The document provides an extensive overview of male reproductive physiology, detailing the stages of spermatogenesis, the anatomy of the male reproductive system, and the hormonal regulation of sperm production. It discusses the physiological processes involved in male sexual function, including erection, lubrication, emission, and ejaculation. Additionally, it explains the mechanisms of sperm maturation and fertilization, highlighting the roles of various glands and enzymes in facilitating reproductive success.

1. Reproductive Physiology
By; T/berhan H.
MSc. Medical Physiology

2. 2
 Process of;
◦ Procreation: maintenance of ones species
◦ Recreational and Relational
 Two types of reproduction
1. Asexual; Binary fission, budding, .....
2. Sexual; involves copulation of male and a female of the
same species
Reproduction

3. 3
 Sexual reproduction results in genetic diversity due to
 Shuffling of genes
 Crossing-over in meiosis and
 Fertilization
 Sexual reproduction produces new individual that is
genetically different from it’s parents
 So new combinations of genes occur in each generation.
….cont

4. 4
 During 7th
week of IUL, bi-potential primordial germ cells
(primitive gonadal cells) appears
 The embryo has a primitive female and male genital tracts
called the Mullerian and Wolffian duct respectively.
 In the absence of Y-chromosome, these germ cells
develop into ovaries
 In the presence of Y-chromosome, the primitive gonadal
cells develop into testis
Development and differentiation of reproductive
organs and tracts

5. 5
 In the absence of functioning testis
◦ The Wolffian duct regresses and
◦ The Mullerian duct develops into the female internal genitalia; the
fallopian tube, uterus and upper 2/3 of vagina
◦ The urogenital slit remains open and the female external genitalia
develops.
 In the presence of functioning testis
◦ Wolffian duct develops into the male internal genitalia, ie,
epididymis, vas deferens, seminal vesicles and prostate
◦ Urogenital slit is closed and male external genitalia (penis and
scrotum) develops

6. 6

7. 7

8. THE MALE REPRODUCTIVE
PHYSIOLOGY

9. Composed of;
 Gonads;
◦ Testes
 Reproductive tract;
◦ Epididymis
◦ Vas deference
◦ Urethra
 External genitalia
◦ Penis;
 Corpora cavernosa
 Corpora spongiousum
 Accessory glands
◦ Prostate
◦ Seminal vessicles
◦ Bulbourethral glands
Functions;
◦ Production of sperm (spermatogenesis)
◦ Delivery of sperm to female
9
Male reproductive system

10. 10
Seminiferous tubule
 There are about 900 coiled
seminiferous tubules in both testis
 Each averaging more than one-half
meter
 Site of sperm production
Epididymis
 Coiled tube which is about 6 meters
long
 The next structure where sperm is
emptied and
 Site of sperm storage

11. 11

12. Male reproductive functions can be divided into three
major subdivisions:
1. Spermatogenesis - formation of sperm cells
2. Performance of the male sexual act
3. Production of hormones
12

13. At embryonic life,
 Primordial germ cells migrate into the testes and
 Become immature germ cells called spermatogonia, which
 Lie in inner surfaces of the seminiferous tubules
During puberty,
 Spermatogonia begin to undergo mitotic division and continually
proliferate and differentiate to form sperm
 It begins at an average of 13 years of age and
 Continues throughout life
 But decreases markedly in old age
 It happens as a result of stimulation by gonadotropic hormones from
anterior pituitary
13
SPERMATOGENESIS

14.  Serious of repeated mitotic cell division happens first
 During these cell divisions spermatogonia migrate toward
the central lumen of the seminiferous tubule along with
Sertoli cells and mature to become primary spermatocytes
14
STEPS OF SPERMATOGENESIS

15.  Then two successive meiotic division happens
 Which are Meiosis I (secondary spermatocyte) and
Meiosis II (spermatids)
 Spermatids are progressively modified to become
spermatozoa (sperm)
 Each spermatids finally have haploid (23) chromosomes
due to the meiotic division
 The whole process takes about 74 days
15
….cont

16.  Among the 23 pairs of chromosomes in each
spermatogonium, one pair is composed of sex
chromosomes (X and Y chromosomes)
 During meiotic division each strand of the sex
chromosome goes to one spermatid
 This determine the sex of the eventual offspring
16

17. 17

18. 18

19. Testosterone;
 Secreted by the Leydig cells
 Essential for growth and division of the testicular
germinal cells - the first stage of sperm cell formation
Luteinizing hormone;
 Secreted by the anterior pituitary gland
 Stimulates the Leydig cells to secrete testosterone
19
Hormones that stimulate
Spermatogenesis

20. Follicle-stimulating hormone;
 Another hormone from anterior pituitary gland,
 Stimulates the Sertoli cells
Estrogens;
 Formed from testosterone by the Sertoli cells when
stimulated by FSH
 Believed to be essential for spermiogenesis
20

21. Growth hormone ;
 Important in controlling metabolic functions of the
testes, as well as
 It promotes early division of the spermatogonia
 In its absence, spermatogenesis is severely deficient or
absent, thus causing infertility.
21

22.  Sperm cell removed from the seminiferous tubules
and/or early portions of the epididymis are non-
motile and cannot fertilize an ovum.
 In the epididymis sperm cells continue to undergo
some developmental stages and continue to get
matured, but
 Still several inhibitory proteins in the epididymal fluid
prevent final motility until after ejaculation.
22
Maturation of Sperm in the Epididymis

23.  Before ejaculation, sperm cells are not motile and can’t
fertilize an ovum
 Full motility is achieved after ejaculation
 Ejaculated sperm cells also have special nutrient fluid
(from Sertoli cells and the epithelium of the epididymis)
 This fluid contains hormones (like testosterone and
estrogens), enzymes, and special nutrients that are
essential for sperm nutrition
23

24.  Each day about 120 million sperm cells are produced
on both tests.
 Majority of these sperm are stored in the epididymis,
but
 Small quantity is stored in the vas deferens
 Can be stored maintaining their fertility for at least a
month
 During this stay, these are kept in a deeply suppressed,
inactive state by multiple inhibitory substances
24
Storage of Sperm in the Testes

25.  Matured fertile sperm can move on fluid medium at
velocities of 1 to 4 mm/min.
 The activity of sperm is greatly enhanced in a neutral
and slightly alkaline medium
 But, it is greatly depressed in a mildly acidic medium.
 Strong acidic medium can cause the rapid death of
sperm.
25
Physiology of the Mature Sperm

26.  Increasing temperature increases the activity of sperm
but so does the rate of metabolism,
 But in such conditions the life span of the sperm cells
is shorter and
 Ejaculated sperm in the female genital tract can stay
only for 1 to 2 days.
26

27.  Matured sperm have head and tail
Head
 The head contains thin cytoplasmic and cell membrane
layer and mainly condensed with nucleus of the cell
 The head on it’s outside anterior 2/3 is covered with a thick
cup called acrosome, which is formed from Golgi apparatus
27

28.  The acrosome contains two main enzymes
 Hyaluronidase enzyme; which can digest proteoglycan
filaments of tissues and
 Powerful proteolytic enzymes; which can digest
proteins
 These enzymes play important roles in allowing the
sperm to enter the ovum and fertilize it
28

29. Tail(flagellum)
 Is the other part of matured spermatozoa which has three
major components:
1. A central skeleton constructed of 11 microtubules,
collectively called the axoneme (similar to that of cilia)
2. A thin cell membrane covering the axoneme
3. A collection of mitochondria around the axoneme in the
proximal portion of the tail (body of the tail).
29

30. 30

31. Motility of sperm
 Achieved by the back-and-forth movement of the tail
which results from a rhythmical longitudinal sliding
motion of the anterior and posterior tubules of the
axoneme.
 This process gets it’s energy from ATP, which is
synthesized by the mitochondria
 Normal sperm move in a fluid medium at a velocity of
1-4 mm/min.
31

32.  Seminal vesicles is lined with a secretory epithelium that
◦ Secretes a mucoid material
◦ With high amount of fructose, citric acid, and other nutrient
substances
◦ It also contains large quantities of prostaglandins and fibrinogen
 Seminal vesicle empties its contents into the ejaculatory duct
which adds greatly to the bulk of the ejaculated semen, and
 So the fructose and other substances in the seminal fluid are
used as a source of nutrient for the ejaculated sperm
32
FUNCTION OF THE SEMINAL
VESICLES

33.  Prostaglandins aid fertilization in two ways:
1. It reacts with the female cervical mucus and make it more
receptive to sperm movement
2. It causes backward, reverse peristaltic contractions in the
uterus and fallopian tubes and this help move the ejaculated
sperm toward the ovaries
33

34.  Prostate gland secretes a thin, milky fluid that
◦ Contains calcium, citrate ion, phosphate ion, a clotting enzyme, and a profibrinolysin.
◦ Is slightly alkaline that helps to neutralize the seminal fluids from the
 Vas deference (due to the presence of citric acid and metabolic end products) and
 Vaginal secretions (pH of 3.5 to 4.0).
 Sperm cell become optimally motile and can fertilize the ovum at pH of 6.0
- 6.5.
 So the slightly alkaline prostatic fluid helps neutralize the acidity of the
other fluids and enhance the motility and fertility of the sperm.
 The average pH of the combined semen is about 7.5, (more than neutralized
by prostatic fluid)
34
FUNCTION OF THE PROSTATE
GLAND

35.  Semen is the fluid ejaculated during the male sexual
act, which is composed of
◦ Fluid and sperm from the vas deferens (10%),
◦ Fluid from the seminal vesicles (60%),
◦ Fluid from the prostate gland (30%), and
◦ Small amounts from the mucous glands, especially the
bulbourethral glands.
 The bulk of the semen is seminal vesicle fluid, which is
the last to be ejaculated and serves to wash the sperm
through the ejaculatory duct and urethra.
35
SEMEN

36. Semen has;
 Milky appearance – due to prostatic fluid
 Mucoid consistency – due to fluid from the seminal vesicles and
mucous glands
 Sticky nature - due to clotting enzymes from the prostatic fluid that
cause the fibrinogen of the seminal vesicle fluid to form a weak fibrin
coagulum that holds the semen in the deeper regions of the vagina
 The coagulum then dissolves during the next 15 to 30 minutes because
of lysis by fibrinolysin formed from the prostatic profibrinolysin.
 In the early minutes after ejaculation, the sperm remain relatively
immobile, possibly because of the viscosity of the coagulum.
 As the coagulum dissolves, the sperm simultaneously become highly
motile
36

37. Life span of sperm;
 For weeks in the male genital ducts
 For only 24 to 48 hours at body temperature
 For several weeks at lowered temperatures, and
 For years when frozen at temperatures below −100°C
37

38.  Sperm cell can’t fertilize an ovum immediately after ejaculation
b/se the inhibitory factors are still present with the ejaculated
semen
 It needs further changes – “capacitation”
 The basic changes are;
1. The uterine and fallopian tube fluids wash away the various
inhibitory factors that suppress the sperm
2. Sperm swim away from the cholesterol vesicles that it covers
towards the uterine cavity so that the membrane at the head of the
sperm (the acrosome) becomes much weaker and allowing release
of it’s enzymes
38
“Capacitation” of Spermatozoa

39. 3. The membrane of the sperm also becomes much more
permeable to calcium ions, so
 Calcium now enters the sperm in abundance and changes
the activity of the flagellum, giving it a powerful
whiplash motion in contrast to its previously weak
undulating motion.
 In addition, the calcium ions cause changes in the cellular
membrane that cover the leading edge of the acrosome,
making it possible for the acrosome to release its enzymes
rapidly and easily as the sperm penetrates the granulosa
cell mass surrounding the ovum, and even more so as it
attempts to penetrate the zona pellucida of the ovum.
39

40.  Acrosome of the sperm contains large quantities of hyaluronidase
and proteolytic enzymes.
Hyaluronidase;
 Depolymerizes the hyaluronic acid polymers in the intercellular
cement
 Open pathways between the granulosa cells so that the sperm can
reach the zona pellucida.
The proteolytic enzymes;
 Digest proteins in the structural elements of tissue cells that still
adhere to the ovum.
 Open a penetrating pathway for passage of the sperm head
through the zona pellucida to the inside of the ovum
40
“Acrosome Reaction” and Penetration of
the Ovum

41.  After a few minutes of the first sperm penetrates the zona
pellucida, calcium ions diffuse inward through the oocyte
membrane and cause multiple cortical granules to be
released by exocytosis from the oocyte into the
perivitelline space.
 These granules contain substances that permeate all
portions of the zona pellucida and prevent binding of
additional sperm, and they even cause any sperm that have
already begun to bind to fall off.
 Thus, almost never does more than one sperm enter the
oocyte during fertilization.
41
Why does only one sperm enter the
Oocyte?

42. Two important areas of initiation
1. Glans penis; most important source of sensory nerve
signals for initiating the male sexual act
 The glans contains an especially sensitive sensory end-
organ system that transmits into the central nervous
system
 Sexual signals from sensory end-organ pudendal
nerve sacral plexus sacral portion of
spinal cord undefined areas of the brain
42
MALE SEXUALACT

43. Signals could also come from;
 Outer nearby structures like the anal epithelium, the
scrotum, and perineal structures
 Internal structures, like in the areas of urethra, bladder,
prostate, seminal vesicles, testes, and vas deferens
43

44. 2. Psychic element of sexual stimulation
 Can greatly enhance the ability of a person to perform the sexual
act
 Can even result in nocturnal emissions during dreams, often
called “wet dreams,”
 So it can be initiated by either
◦ Psychic stimulation from the brain or
◦ Actual sexual stimulation from the sex organs, but
◦ Usually it is a combination of both
Integration of the male sexual act in the Spinal Cord
 Male sexual act is mainly integrated in the spinal cord (sacral
and lumbar spinal cord)
44

45. STAGES OF THE MALE SEXUAL ACT
Penile Erection - Parasympathetic Nerves
 Is the first effect of male sexual stimulation,
 Degree of erection is proportional to degree of stimulation,
 Release of nitric oxide and/or vasoactive intestinal peptide
 Relaxation of the arteries of the penis and the trabecular
meshwork of smooth muscle fibers in the erectile tissue of
the corpora cavernosa and corpus spongiosum
45

46.  The erectile tissue consists of large cavernous sinusoids that are
normally empty of blood
 But become dilated when arterial blood flows rapidly into them
under pressure while the venous outflow is partially occluded
 The two corpora cavernosa, are surrounded by strong fibrous
coats; therefore,
 High pressure within these sinusoids causes ballooning of the
erectile tissue
 Then the penis becomes hard and elongated – erection
46

47. 47

48. Lubrication - Parasympathetic NS
 During stimulation, the PNS impulses stimulate the
urethral and bulbourethral glands to secrete mucus.
 This mucus flows through the urethra during
intercourse to aid in lubrication during coitus
 But, most of the lubrication of coitus is provided by the
female sexual organs
 Without adequate lubrication, intercourse causes
grating and painful sensations that inhibit sexual
sensations
48

49. Emission and Ejaculation – Sympathetic NS
 Final stages of sexual act
 When the sexual stimulus reaches it’s climax,
sympathetic impulses start to be emitted from the reflex
centers of the spinal cord
 It leaves the cord at T12 - L2 and pass to the genital
organs through the hypogastric and pelvic sympathetic
nerve plexuses
49

50. Emission;
 Begins with contraction of the vas deferens and the ampulla
to cause expulsion of sperm into the internal urethra.
 Then, contractions of the muscular coat of the prostate gland
followed by contraction of the seminal vesicles expel
prostatic and seminal fluid also into the urethra.
 All these fluids mix in the internal urethra with mucus
secreted by the bulbourethral glands to form the semen.
 This all is the process of emission.
50

51. Ejaculation;
 The filling of the internal urethra with semen elicits
sensory signals that are transmitted through the
pudendal nerves to the sacral regions of the cord,
giving the feeling of sudden fullness in the internal
genital organs.
 These sensory signals further excite rhythmical
contraction of the internal genital organs and cause
contraction of the ischiocavernosus and
bulbocavernosus muscles that compress the bases of
the penile erectile tissue.
51

52.  These together increases the pressure in the erectile
tissue of the penis, genital ducts and urethra
 This helps “ejaculate” the semen to the exterior -
ejaculation
 At the same time, rhythmical contractions of the pelvic
muscles and some of muscles of the body trunk causes
 Thrusting movements of the pelvis and penis, which
also help propel the semen into the deepest recesses of
the vagina
52

53.  This entire period of emission and ejaculation is called
the male orgasm.
 At its termination, the male sexual excitement
disappears almost entirely within 1 to 2 minutes and
erection ceases, a process called resolution.
53

54. Secretion of Testosterone
 The testes secrete several androgens which are also called male sex
hormones
 These including testosterone, dihydrotestosterone, and
androstenedione
 Testosterone is more abundant and considered as the primary testicular
hormone
 But, much of the testosterone is eventually converted into the more
active hormone dihydrotestosterone in the target tissues
54
TESTOSTERONE AND OTHER
MALE SEX HORMONES

55.  Testosterone is formed by the Leydig cells
 Leydig cells;
◦ Found in the interstices between the seminiferous tubules and
◦ Constitute about 20% of the mass of the adult testes
◦ Are numerous in newborn in the first few months of life and
after puberty
◦ Are less easily destroyed by x-ray or excessive heat
55

56.  Androgens are also produced elsewhere in the body
besides the testes
1. Adrenal gland
◦ But it doesn’t have significant masculinizing effect
◦ However, in tumorous conditions significant amount may be
produced and cause male secondary sexual characteristics, even
in the female
2. Ovary also produces minute/insignificant quantities of
androgens
 All androgens are steroid and can be synthesized either
from cholesterol or directly from acetyl coenzyme A.
56

57.  About 97% of testosterone becomes either
◦ Loosely bound with plasma albumin or
◦ More tightly bound with beta globulin and
◦ Circulates in the blood in these states for 30 minutes to several
hours.
 Then it is either transferred to the tissues or degraded into
inactive products that are subsequently excreted
 Much of the testosterone fixed to the tissues is converted
to dihydrotestosterone, especially in certain target organs
57
Metabolism of Testosterone

58.  The testosterone that does not become fixed to the
tissues is rapidly converted in to other forms mainly by
the liver
 Then excreted either into the gut by way of the liver bile
or into the urine
58

59. Estrogen production
 Small amounts of estrogens are also formed in the male
(about 1/5th
of non-pregnant female)
 The exact source isn’t known, but the following are the
possible sources:
1. Conversion of testosterone to estradiol by Sertoli cells
2. Formation of estrogen from testosterone and
androstanediol by other tissues (liver)
59

60. 60

61.  Generally, testosterone is responsible for masculinization of
the body
Functions of Testosterone During Fetal Development
 Is responsible for the development of the male body
characteristics, including the formation of a penis and a
scrotum
 It also helps formation of prostate gland, seminal
vesicles, and male genital ducts
 It also suppresses the formation of female genital
organs.
 Testosterone is the main stimulus for decent of testes
61
FUNCTIONS OF TESTOSTERONE

62. Effect on Development of Adult Primary and Secondary
Sexual Characteristics
 After puberty, testosterone cause the penis, scrotum,
and testes to enlarge about eightfold before the age of
20 years.
 Causes the secondary sexual characteristics of the male
to develop, starting from puberty
 Also causes growth of hair in different body parts;
pubis, linea alba, face, chest, …
62

63.  Testosterone causes male pattern baldness
 Testosterone also causes masculine voice (causes
hypertrophy of the laryngeal mucosa and enlargement
of the larynx)
 Testosterone increases thickness of skin and contribute
to the development of acne
 Testosterone increases protein formation and muscle
development
63

64.  Testosterone increases bone matrix and causes calcium
retention
 Testosterone increases the basal metabolic rate
 Testosterone increases red blood cells
 Effect on electrolyte and water balance
◦ Has a little effect on electrolytes, but still increases
◦ Blood and ECF volume (increases by 5-10% of body wt)
64

65.  Most of the effects result basically from increased rate of protein formation
 So basically testosterone enters the cell and is converted to
dihydrotestosterone with the action of 5α-reductase
 This in turn binds with cytoplasmic receptor protein and enters the nucleus
 Then it binds with nuclear protein to induce DNA-RNA transcription
 Then RNA concentration increases which progressively rising the cellular
proteins
 The number of DNA also rises increasing the number of cells too
65
BASIC INTRACELLULAR MECHANISM
OF ACTION OF TESTOSTERONE

66. GnRH;
 Is secreted by neurons in the hypothalamus and released
into the hypothalamic-hypophysial portal vascular system.
 GnRH is then transported to the anterior pituitary gland in
the hypophysial portal blood
 Then it stimulates the release of the two gonadotropins, LH
and FSH
66
CONTROL OF MALE SEXUAL FUNCTIONS BY
HORMONES FROM THE HYPOTHALAMUS AND
ANTERIOR PITUITARY GLAND

67.  GnRH is secreted for a few minutes at a time once
every 1-3 hours – pulsatile release of GnRH
 It’s secretion is determined by
1) The frequency of these cycles and
2) The quantity of GnRH released in each cycle
 The rate of FSH release is slightly affected by this
pulsatile release of GnRH, rather
 It changes more slowly over a period of many hours in
response to long term changes in GnRH
67

68.  But, the secretion of LH is also cyclical, which follows
the pulsatile release of GnRH.
 Because of this closer relation between GnRH and LH
secretion, GnRH is also widely called LH-releasing
hormone
68

69. 69

70. Gonadotropic Hormones: LH and FSH
 These are glycoprotein hormones secreted by the same cells of
anterior pituitary gland, called gonadotropes.
 Almost no LH or FSH are secreted in the absence of GnRH
 Testosterone secretion by Leydig cells only occurs when
stimulated by LH from the anterior pituitary gland and
 The rate of secretion is almost proportional and
 Anterior pituitary gland secretion of LH and FSH is inhibited
by testosterone-Negative feedback control
70

71. Role of FSH and Testosterone on Spermatogenesis
 Both FSH and testosterone are obviously necessary for
spermatogenesis
 FSH binds with specific FSH receptors at the Sertoli cells
 This causes the Sertoli cells to grow and secrete various
spermatogenic substances.
 Simultaneously, testosterone (and DHT) diffusing into the
seminiferous tubules also
 Cause strong tropic effect on spermatogenesis
71

72. Role of Inhibin in Negative Feedback Control
 This hormone has a strong direct effect on the anterior
pituitary gland to inhibit the secretion of FSH
 It operates with and in parallel of the negative feedback
mechanism for control of testosterone secretion
72

73. Human Chorionic Gonadotropin
 Secreted by the placenta and circulates both in the
maternal and fetal circulation
 Stimulates testosterone secretion by the fetal testes
 Has almost the same effects on the sexual organs as LH
73

74. Female Physiology Before
Pregnancy and Female Hormones
By; T/berhan H.
MSc in Medical Physiology

75. Composed of;
 Gonads;
◦ Ovaries
 Reproductive tract;
◦ Uterine (fallopian) tube
◦ Uterus
◦ Vagina
 External genitalia
◦ vulva;
 Vaginal opening
 Clitoris
 Labia minora/majora
 Accessory glands
◦ Vestibular glands
Functions;
◦ Production of ova (oogenesis)
◦ Reception of sperm from male
◦ Transport of ova
◦ Maintenance of developing fetus
◦ Childbirth (parturition)
75
Female reproductive system

76. Female reproductive system
Composed of;
• Gonads;
– Ovaries
• Reproductive tract;
– Uterine (fallopian) tube
– Uterus
– Vagina
• External genitalia
– vulva;
• Vaginal opening
• Clitoris
• Labia minora/majora
• Accessory glands
– Vestibular glands
Functions;
• Production of ova
(oogenesis)
• Reception of sperm and
fertilization
• Transport of ova
• Maintenance of developing
fetus
• Childbirth (parturition)
76

77. 77

78. 78

79. OOGENESIS AND FOLLICULAR
DEVELOPMENT
• Oogenesis; differentiation of developing egg
(oocyte) into a mature egg (ovum)
• Starts with migration of primordial germ cells
First from the dorsal endoderm of the yolk sac to
the outer surface of the ovary – with repeated cell
division
Then further into the substance of the ovarian
cortex - now called oogonia or primordial ova
79

80. ….cont
• Then each oogonia collects spindle cells from the
ovarian stroma around it and
• These cells take on an epithelioid characteristics which
are then called granulosa cells.
• The ovum at this stage is now called primordial follicle
(primary oocyte)
• By the fifth month of fetal development, the oogonia
completes mitotic replication and prophase I
80

81. …cont
• From then, mitotic cell division ceases and no additional
oocytes are formed
• At birth there are about 1 to 2 million primary oocytes
At puberty
• Meiotic cell division of the oocyte continues and completes
meiosis I
• So, each oocyte divides and gives a large secondary oocyte
(ovum) and a small first polar body where both containing 23
pairs of chromosomes
81

82. ….cont
• The first polar body disintegrates with/without second
meiotic division
• The ovum then starts second meiotic division, and paused
at metaphase II
• If fertilization occurs meiosis II will continue and
complete it’s stages
• Half of the sister chromatids remain in the fertilized ovum
and the other half are released in the second polar body
82

83. ….cont
• At puberty, only a small percentage of the only
300,000 oocytes remained in the ovaries become
mature
• Out of these, only 400 to 500 of the primordial
follicles develop enough to expel their ova (one
each month) during reproductive life (13-46 years
of age)
• The remaining thousands of oocytes degenerate
83

84. 84

85. FEMALE HORMONAL SYSTEM
Consists of three hierarchies of hormones
• Hypothalamic hormone - GnRH
• Anterior pituitary hormones – FSH and LH
• Ovarian hormones - estrogen and progesterone
Secretion;
• GnRH is secreted in short pulses once every 90 minutes like in males
• But the secretion rate of the other hormones during the monthly
sexual cycle is quite different
85

86. 86

87. MONTHLY OVARIAN CYCLE;
• Average monthly sexual cycle is 28 days (20-45)
• Two importance;
1. Release of single ovum each month
2. Preparation uterine endometrium for implantation
The monthly ovarian changes are completely due to the
gonadotropic hormones, FSH and LH
In the absence of these hormones, the ovaries remain
inactive
Starts at puberty (age of 11-15 years) 87

88. 1) FOLLICULAR PHASE OF THE OVARIAN
CYCLE
• At birth each ovum is surrounded by a single
layer of granulosa cells – which is called
primordial follicle
• Till puberty the granulosa cells;
1. Provide nourishment and
2. Secrete an oocyte maturation inhibiting factor
(that keeps them in prophase I)
88

89. • At puberty; higher amount of FSH and LH is
secreted
• The ovaries with some of the follicles within it
begin to grow
• The first stage of follicular growth begins with
Moderate enlargement of the ovum, (twofold to
threefold)
Growth of additional layers of granulosa cells
Which are now called primary follicles
89

90. Development of Antral and Vesicular Follicles
• FSH, cause accelerated growth of 6 - 12 primary
follicles each month
• Rapid proliferation of the granulosa cells, giving
rise to many more layers
• Then spindle cells (from the ovary interstitium)
collect around the granulosa cells, giving rise to
a second mass of cells called the theca
90

91. • Theca has two cell layers
1. Theca externa – is the outer layer
 Develops into a highly vascular connective tissue
capsule
 Becomes the capsule of the developing follicle
2. Theca interna – inner layer
 Develops an epithelioid nature like the granulosa
cells and
 Develop the ability of secreting additional steroid
sex hormones (estrogen and progesterone)
91

92. • After days of proliferative phase of growth,
granulosa cells secretes a follicular fluid that
contains a high concentration of estrogen
• As a result an antrum appears within the mass
of granulosa cells
• This whole growth of primary follicle up to the
antral stage is stimulated by FSH alone
92

93. • Then even larger follicles called vesicular follicles
develops more rapidly as a result of;
1. Increased number of FSH receptors formed by
granulosa cells due to the secretion of estrogen in to
the follicle. This makes the granulosa cells even more
sensitive to FSH – positive feedback
2. Both FSH and estrogen promote LH receptors on the
granulosa cells, allowing LH stimulation and creating
an even more rapid increase in follicular secretion.
3. The increased estrogen and LH act together to cause
proliferation of the follicular thecal cells and increase
their secretion as well.
93

94. • Then antral follicles begin to grow rapidly
• The ovum itself enlarges with about 3-4 fold in
diameter, resulting in total increase of up to
10-fold, or a mass increase of 1000-fold.
• As the follicle gets enlarged, the ovum is kept
at one pole of the follicle surrounded in a mass
of granulosa cells.
94

95. • Only one follicle fully matures each month
– Outgrowth of one follicle and atresia of the other all (5 - 11
developing follicles), and the probable reason is
– The negative feedback of estrogen from the most rapidly growing
follicle causing on hypothalamus, where
– The largest follicle continues to grow due to its intrinsic positive
feedback effects
– This is important because it prevents development of more than
one child in each pregnancy
– At ovulation, only a single follicle matures with a diameter of 1 -
1.5 cm & called the mature follicle
95

96. 96

97. Ovulation
• Through the process of rapid follicular development a
protruding outer wall of the follicle begins to swell like a nipple
called stigma
• Then, fluid begins to ooze from the follicle through the stigma,
that later ruptures widely and allowing a more viscous fluid,
which has occupied the central portion of the follicle, to
evaginate outward.
• This fluid carries with it the ovum surrounded by corona radiata
(mass of several small granulosa cells).
• Ovulation occurs 14 days after the onset of menstruation in a woman
with 28-days of female sexual cycle.
97

98. A surge of LH is needed for ovulation
• 2 days prior to ovulation, LH secretion rises 6 - 10 fold &
peaks about 16 hours before ovulation
• Similarly FSH increases 2-3 fold and
• Both FSH and LH act synergistically to cause rapid swelling
just a few days before ovulation.
• The LH also causes the granulosa and theca cells mainly
secrete progesterone
• As a result rate of estrogen secretion falls about 1 day before
ovulation
98

99. Initiation of ovulation
• LH causes the rapid secretion of follicular steroid hormones
mainly containing progesterone
• This in turn causes two main events to happen which are
important for ovulation:
1. Release proteolytic enzymes from lysosomes by theca externa
 Causing degeneration and weakening of the stigma wall and
 Further swelling of the entire follicle
2. Rapid growth of new blood vessels into the follicle wall, and
secretion of prostaglandins (local vasodilators)
• As a result of these two events there will be transudation of
plasma into the follicle that furthers add to the swelling
• Finally, the follicular swelling & degeneration of the stigma
causes rupture of the follicle and discharge of the ovum.
99

100. 100

101. 2) LUTEAL PHASE OF THE OVARIAN
CYCLE
• After a few hours of ovum expulsion, the remaining granulosa
and theca interna cells change rapidly into lutein cells
• These cells enlarge in diameter (>2x) and become filled with
lipid inclusions that give them a yellowish appearance
• This process is called luteinization, and the total mass of cells
together is called the corpus luteum
• A well-developed vascular supply also grows into the corpus
luteum
101

102. • The granulosa cells in the corpus luteum form
large amounts of the female sex hormones
progesterone and estrogen (more progesterone
than estrogen) and
• The theca cells form mainly androgens
(androstenedione and testosterone)
• However, most of these hormones are converted
into estrogens by the aromatase enzyme in the
granulosa cells
102

103. • The corpus luteum will have about 1.5 cm of
diameter after 7 - 8 days of ovulation.
• Afterwards it begins involute and eventually
loses its
– Secretory function
– Yellowish and lipid characteristic and
– Becomes the corpus albicans that is replaced by
connective tissue which is finally absorbed
103

104. Luteinizing Function of LH ;
• LH is responsible for the conversion of granulosa
and theca interna cells into lutein cells
• This function gives LH its name - “luteinizing,”
for “yellowing”
• Until ovulation local hormone in the follicular
fluid, called luteinization-inhibiting factor, hold
the luteinization process in check
104

105. Secretion by the Corpus Luteum (role of LH):
• Corpus luteum is a highly secretory organ, that continues to
secrete large amounts of progesterone and estrogen
• Once LH (mainly secreted during the ovulatory surge) has acted
on the granulosa and theca cells,
• The newly formed lutein cells seem to be programmed to go
through predetermined sequence of
1. Proliferation
2. Enlargement, and
3. Secretion, followed by
4. Degeneration
• All this occurs in about 12 days.
105

106. Involution of Corpus Luteum and onset of next ovarian cycle
1. Estrogen in particular and progesterone to a lesser
extent, have strong feedback effects in maintaining low
levels of FSH and LH
2. Similarly inhibin hormone secreted by lutein cells also
inhibits FSH secretion
• Both thess causes low secretory rates of FSH and LH
• Low or total loss of FSH and LH finally causes the corpus
luteum to degenerate completely
• This process called involution of the corpus luteum.
106

107. • This happens at the end of 12th
day of corpus luteum
life (26th
day of the sexual cycle) which is 2 days
before menstruation begins.
• The sudden cessation of estrogen, progesterone, and
inhibin secretion by the corpus luteum removes the
feedback inhibition of the anterior pituitary gland,
• This results in the secretion increased amounts of
FSH and LH again and
• Beginning of new ovarian cycle
107

108. Monthly Uterine Cycle
• Refers to cyclical changes in the endometrial lining of the uterus
• Resulting in an overt bleeding from the genital tract
• Also called endometrial cycle
• Is the period between menstrual flows
• Involves cyclic rise and fall in female reproductive hormones
• Is variable at the extremes of reproductive ages
Rationale
• Periodic preparation for fertilization + pregnancy
108

109. A. Proliferative Phase (Estrogen phase)
 Begins with the last days of menses and ends around ovulation
 Dominant ovarian hormone: estrogen
Main events;
a. Stroma & epithelium:
•↑ Proliferation and growth of epithelial + stromal cells.
•At the time of ovulation the endometrium regains its thickness (3 - 5 mm thick)
b. Glands:
• Progressive growth of endometrial glands
• Cervical epithelium secrets a thin, watery mucus
c. Angiogenesis:
• Lengthening of the vessels
• Neovascularization of layers
d. Receptors:
• ↑Estrogen + progesterone receptors on endometrial cells
109

110. 110
Uterine gland
Uterine artery
Uterine lumen
Organization of glands and blood flow within the uterine endometrium

111. B. Secretory Phase (Progestational Phase)
a. Duration: 14th
- 28th
day.
b. Predominant hormone:
• Progesterone (10x, corpus luteum).
• Estrogen
c. Epithelium and stroma:
• Marked secretory changes and swelling of the endometrium
• Further thickening of endometrium
• All these changes are important for implantation of fertilized ovum
• ↑ Adhesivity of surface epithelium.
d. Mucous glands:
• Elongation and coiling
• Secrete thick viscous fluid
• Glycogen
• Cervical mucus becomes thick
f. Angiogenesis:
`
• Spiraling of the blood vessels
• ↑ Vascularity
g. Receptors:
• ↓ Number of estrogen + progesterone receptors.
111

112. Organization of glands and blood flow within the uterine endometrium
112

113. C. Menstrual Phase
I. If no fertilization + no production of hCG, CL involutes →↓E, P
(Luteolysis/luteal regression).
Then 3 events follows to cause menstrual bleeding
a. ↓ E, P → ↓ stimulation of endometrial cells → rapid involution
of the endometrium → ↑ local Pgs
b. Then, vasospasm of the tortuous blood vessels (due to Pgs) →
↓nutrients → ischemia and necrosis → formation of hemorhagic
and edematous layer, then
c. Desquamation and separation of the necrotic outer layer →
initiation of uterine contractions that expel the uterine contents
→ bleeding
II. If conception occurs: the functional life span of corpus luteum is
extended (due to hCG)
113

114. 114

115. 115
Normal menstrual cycle:
a. Duration: 2-8 d
b. Cycle length: 21-35 d (28 + 7)
c. Vol. blood loss: 20-150ml (aver. 50ml).
d. Type of blood flow: 75% arterial, 25% venous.
e. Contents: tissue debris, Pgs, fibrinolysin
f. No clot formation:
but, (if no fibrinolysin + excessive bleeding → clot formation)

116. 116
Cervical Cycle
Quantity + quality of mucus is changed
i. E: → Profuse, watery, alkaline (penetrability by sperm is maximal)
ii. P: scanty, viscous, infiltration with cellular elements
Vaginal cycle
i. E: ↑Cornification (hardening), ↑ acidophilic cells (Pap smear)
ii. P: Thick mucus, infiltration with PMNL, ↓acidophilic cells

117. 117
Cyclic Changes in the Breasts
• E: Proliferation of mammary ducts.
• P: causes growth of lobules and alveoli.
• Distention of ducts/hyperemia + edema → breast swelling,
tenderness & pain.

118. 118
The cycle of ovulation and menstruation

119. 119
Physiological and behavioral variables
1. Core body temperature
• 0.5°C in the luteal phase/oral or rectal.
• Progesterone/resetting thermostat center + thermogenic effect.
2. Sensory acuity
• Olfactory acuity (menstrual synchronization).
3. Sexual activity
• Human female sexual behavior around the mid-cycle
( Androgens)
4. Eating behavior and body weight
•  Food intake in luteal phase ( 5-HT activity).

120. 120
Hypothalamic – Hypophyseal - Ovarian Axis
Purpose
a. Production of physiologic quantities of sex steroids
b. Generation of healthy ova that become mature female gamets

121. 121
Components
a. Hypothalamic GnRH/LHRH Hypophysis
Neural
b. Hypophyseal Gns Ovary
LH, FSH
c. Ovary
i. Granulosa cells Estradiol/inhibin/activin
ii. Thecal cells Androgens/estradiol
 Negative feedback
 Positive feedback control

122. 122
Negative Feedback

123. 123
Positive Feedback Negative Feedback
?
?

124. 124
Hypothalamus
GnRH
Gonadotropes
LH FSH
Theca cells Granulosa cells
Androgens
Inhibin
+
¯
+ +
+
Estradiol
¯
¯
Chronic illness
Weight & fat loss
Stress, drugs, exercise
¯
GnRH analogues
• Breast Ca.
• Endometriosis
• Leiomyomas
Summary of H-P-O axis

125. The Physiology of Ovarian Hormones
1) Estrogens (17β-estradiol, estrone, estriol)
a. Biosynthesis;
Origin: Ovary: granulosa cells + theca cells
Corpus Luteum
Placenta/pregnancy
Adrenal cortex
Testis (Males: Sertoli cells, aromatization)
Chemistry
Precursors: Cholesterol/C-27 Animal fat in the diet,
De Novo synthesis.
125

126. b. Secretion and bioavailability;
•98% is found bound to carrier proteins.
38% to sex hormone binding globulin (SHBG)
60% to plasma albumin
•2% exist in free form.
c. Metabolism:
Liver → bile, urine
126

127. 2) Progestins: Progesterone
17α-hydroxyprogesterone
Origin: Ovarian follicles
Corpus luteum
Placenta/pregnancy
Adrenal cortex
Testes/males
127

128. Synthesis
• Cholesterol (C-27) → C-21 steroid
Bioavailability
•Bound to: 80% to albumin
18% transcortin (CBG)
2% Free
Metabolism: Liver (urine)
128

129. The Physiological adjustments to Pregnancy
a. Amenorrhea
b. Morning sickness
•4th
-5th
week of pregnancy/peak at the 8th
week.
• Disappears at 14th
week.
•??? hCG
•??? Steroids of pregnancy→↓ Intestinal motility
129

130. 130
c. Enlargement of reproductive tract
•Ovary: ↑ size/∵ CL of pregnancy.
•Uterus: 50gm → 1100gm (volume = stretching + hypertrophy).
• Cervix: ↑
• Vagina + vulva: ↑
•Breasts: ↑ (2x)
d. Acromegalic features
e. Weight gain:  11-12.5kgs
oFetus = 3.5kgs
oAmniotic fluid, placenta + fetal membranes = 2kgs
oUterus = 1kg
oBreasts = 1kg
oBlood & ECF = 2.5kg
oFat = 1 kg

131. 131
• ↑Appetite + food intake/hormonal + flow of substrates from the maternal
blood to the fetus
f. BMR: ↑10-15% (↑T4
, ↑sex steroids, ↑adrenocortical hormone).
(To supply energy that is expended to carry the extra load.)
g. Hematological changes:
•  Blood volume: 40-45% (Plasma volume +RBC mass/450ml, plasma>RBC)
• ↑Plasma volume → haemodilution → Physiological anaemia
(↓ RBC count, ↓ Hb, ↓ Hct).
• ESR (plasma globulins, fibrinogen).
•  Fe requirement

132. Significance of volume expansion:
• It meets the metabolic demands of the enlarged uterus and its greatly
hypertrophied vascular system.
• It provides abundant nutrients and elements to support the rapidly
growing placenta and fetus.
• It protects the mother, and in turn the fetus, against the deleterious
effects of impaired venous return in erect positions.
• It safeguards the mother against the adverse effects of parturition-
associated blood loss.
132

133. Δs in total blood volume + plasma + RBC volumes during pregnancy
133

134. 134
h. Cardiovascular
• ↑ CO (35%, 27wks) → ↑ HR, ↑SV (Placenta: A-V shunt).
• ↑ Venous return
• ↑ Blood flow: lungs, skin, kidneys, GIT, coronaries and breasts).
• ↑ Blood volume: 1-1.5l
• ↑ Uteroplacental blood flow: uterus, placenta/625ml/min.

135. I. Renal
• ↑ GFR/50% → ↑ Urine output
i. Hypervolemia-induced haemodilution lowers the protein
concentration and oncotic pressure of plasma entering the
glomerular microcirculation.
ii. Renal plasma flow increases by approximately 80%
• Gravid uterus compresses the bladder + ↓volume capacity →
↑frequency of urination
135

136. 136
Cardiovascular and renal changes in pregnancy

137. J. Respiration
• ↑ O2
requirements (30%).
• ↑ Minute ventilatory volume/↑30-50%
i. To supply the fetus + to support the increased metabolic rate.
ii. Progesterone increases sensitivity of respiratory chemoreceptors
to CO2
+ ventilation is adjusted to keep the arterial PCO2
lower
than normal.
• ↑ Tidal volume, inspiratory capacity
•  Peak expiratory flow rate
137

138. • Airway conductance, Total pulmonary resistance.
• ↓ Functional residual capacity (↓Expiratory reserve +↓Residual volume).
• ↓ Total lung volume, ↓ Inspiratory reserve.
• Total lung capacity remains unchanged.
• Expanding uterus pushes the abdominal viscera up against diaphragm
and interferes with breathing/↑RR.
138

139. k. Immune system
• Cell-mediated immunity is suppressed
(Maintenance of pregnancy + protection of the fetus, progesterone).
l. GIT
• ↑ Gastric emptying time, ↓ intestinal motility → constipation
(↑ Progesterone).
• ↓ lower esophageal sphincter tone → reflux esophagitis or
‘Heartburn’ (↑ Progesterone).
139

140. 140
m. Integumentary system
I. Hyperpigmentation (   MSH).
• ↑ Melanocyte activity:
Darkening of the areola.
Linea nigra (mid line below umbilicus)
• Temporary darkening of the skin (nose, cheeks – ‘Mask of
pregnancy’, chloasma).
 ↑ Gravid uterus→ stretching the dermis-tears the collagen tissue →
striae gravidarum/reddish → silver white/
II. Vascular changes (hyperestrogenemia).
• Angiomas/spider angiomas (face, neck, upper chest, and arms).
• Palmar erythema

141. 141
n. Endocrine system
i.Anterior pituitary
• ↑ 50% increment in size, ↑ TSH, ↑ Prolactin.
• ↓ FSH, LH/∵ inhibitory effect of E + P from the placenta.
• ↓ GH
ii. Adrenal cortex
• ↑Plasma glucocorticoids
• ↑ Aldosterone/2x → ↑ salt + H2
O retention/hypertension.

142. 142
iii. Thyroid Gland (↑50%)
• ↑TSH → ↑ T3
, T4
→ ↑ BMR
iv. Parathtyroid Glands
• ↑ Size → ↑ PTH → mobilize Ca2+
from the mother’s bone to make
it available to the fetus

143. 143
v. Relaxin (Corpus Luteum & placenta)
a.Remodeling of the pelvic girdle, softening of the Cx + the
vagina
b.Cervical softening, effacement + dilatation, decrease time to
delivery
c.Laxity of pelvic joints and separation of the pubic symphysis
d.Relaxin + Progesterone → inhibit myometrial contractions →
quiescence → maintenance of pregnancy

144. The Endocrine Placenta
Placental Functions: Respiratory, Nutritive, Excretory, Endocrine
o Maintains a quiescent gravid uterus
o Maternal physiology to ensure fetal nutrition in utero.
o Maternal pituitary function + mammary gland development
o Determines the time of labor and delivery.
o Source of hCG
144

145. 145
Role of the placenta in exchanges between the fetal & maternal compartments

146. 146
Peptide hormones: hCG + hPL
Others: Relaxin, inhibin, GnRH, ACTH, CRH, TRH, IGFs
β-endorphin,

147. 147
Human chorionic gonadotropin (hCG)
• Origin: syncytiotrophoblast of the placenta.
• Synthesis: glycoprotein, 236aa, 38kd, 2 noncovalently linked
subunit (α, β)
• Homology: LH, FSH, TSH
(Luteinizing + Luteotropic).
• Secretion and plasma
o 6-8d after conception
o Peak: 60-90d
o Plateauing: 120d before delivery.
o After delivery: 12-24hrs.

148. o ↑ hCG: Multiple pregnancy
Rh – isoimmunization
Diabetic woman in pregnancy
Choriocarcinoma
o  hCG: Ectopic pregnancy
Miscarriage ….???abortion
148

149. 149
• Function:
a. Maintain the early corpus luteum of pregnancy (LH).
b. Promote steroidogenesis.
c. Regulate the development + secretion of T by the fetal testes
d. Give immunological privilege to the developing trophoblast.

150. 150
Circulating levels of hCG in maternal blood during pregnancy.

151. 151
Human Placental Lactogen (hPL, CGP, hCS)
•Origin: syncytiotrophoblast
•Chemistry: a single chain polypeptide
•Homology: GH
•Secretion & Plasma
o 3rd
week after conception.
o Appears at plateau at term.
o [hPL]  placental weight.
•Nature
o Mainly - lactogenic activity
o 3% - growth promoting activity
o t½ = 20min (it can not be detected after birth).

152. 152
• Functions
a. Spares maternal glucose → providing continued nutrition for the
developing fetus (insulin-resistance state).
b. hPL exerts metabolic effects in pregnancy similarly to those of GH.
i. Stimulation of lipolysis → ↑ free FA (accelerated starvation).
ii. Inhibition of glucose uptake in the mother → development of
maternal insulin resistance (diabetogenic).
iii. Inhibition of gluconeogenesis →↑ transportation of glucose and
protein to the fetus.

153. Placental Steroid Hormones
1. Progesterone
•Source and synthesis: maternal cholestrol, trophoblast
•Functions:
a.Progesterone binds to receptors in uterine smooth muscle
→↓RMP
→ inhibiting smooth muscle contractility →myometrial quiescence
→ prevents premature expulsion of fetus
b. Secretory endometrium → decidua/histiotropic + hemotropic nutrition.
c. Inhibits Pgs formation and other paracrine factors
d. Maintenance of pregnancy: inhibit T-lymphocyte cell-mediated
response
e. Breasts: lobuloalveolar development.
153

154. 154
Maternal serum level of progesterone during pregnancy

155. 155
2. Estrogen
•Origin: Corpus luteum (early wks of preg.) +
syncytiotrophoblast
•Urinary estriol excretion of the mother → index of the state of
the fetus
•It should be steadily increasing throughout pregnancy if the
fetus is growing normally
Functions:
a. Stimulate Pg synthesis
•↑ Uterine blood flow (↑fetal organ maturation + development)
b. Mediate the growth + development of the maternal reproductive
organs
c. Stimulates phospholipid synthesis + turnover

156. 156
Maternal serum levels of estrogens during pregnancy

157. 157
Secretion rates of placental hormones

158. The Physiology of Parturition
1. Defiition  delivery of the baby
•Duration of gestation; 40wks
2. Mechanisms: not known completely
 Mechanical factors
a.Distension of uterus (fetal age size) → ↑ stretching of
smooth muscle, inherent rhythmicity) → ↑ contractility.
158

159. b. Uterine contractions (Braxton Hicks contractions +ve feedback)
↑ Distension + effect of hormones
↓
Uterine contractions
↓
The increased pressure of the baby’s head against the cervix with each
contractions excites the fundus or body of the cervix to contract
↓
Dilatation of cervix & distension of vagina.
↓
Stimuli from the cervix + vagina
↓
↑ Secretion of oxytocin
↓
↑ Uterine contraction until they are strong enough to expel the baby
159

160.  Neuroendocrine factors
a. Progesterone withdrawal
•↓ P at the end of gestation period →↓No. of myometrial
progesterone receptors
•↓ Antagonistic effect of progesterone to oxytocin + Pgs
•↓ Progesterone → synchronizing uterine contractions
160

161. 161
b. Estrogen
•↑ E (in amount) →↑ prostaglandin synthase activity in the
tissues
of the uterus + fetal membrane →↑ myometrial contractions.
•↑ E →↑ myometrial + endometrial oxytocin receptors.
•↑ E →↑ oxytocin production & secretion by the
neurohypophysis
c. Oxytocin
•↑ Uterine contractions/distension + E.
•↑ Oxytocin →↑Pg → stimulate uterine smooth muscle
contraction → expulsion of the fetus

162. 162
d. Relaxin
•Relaxes the pubic ligaments + relaxes the lower part of the uterus.
•Ripen/soften cervix → so eases the passage of the offspring at
birth.
•↑ Sensitivity of the uterus to oxytocin.
e. Prostaglandins
•↑ E →↑Pg synthesis →↑ Intracellular Ca2+
in the myometrium
→ uterine contractions
•Act synergistically with oxytocin/cervical ripening, softening,
dilatation, contractions

163. 3. Mechanics of Labor
a.Uterine contractions begins at the fundus + spread downward
over
the body of the uterus
b. Intensity of contraction is stronger at the fundus than in the lower
segment of the uterus - force the baby downward toward the cervix
c. Frequency of contractions: onset: once in every 30min
later: once in 1 to 3 min.
 Intermittent contraction will not stop the blood flow thru the placenta and
the fetus will not die.
163

164. 164
d. Stages
• 1st
stage: the period from onset of labor up full cervical
dilatation - (8-24hrs or less)
• 2nd
stage: the time interval from the full dilatation of the cervix
till delivery of fetus (hrs to minutes)
• 3rd
stage: the time taken for separation and delivery of the
placenta (10-45min)
• Duration of each stage tends to be longer in a primipara than in a
multipara

165. The Mammary Glands and Lactation
• Mammary glands: replaces the nourishing function of the placenta
after birth.
• Lactation → evolutionarily conserved mammalian physiological
function.
1. Mammogenesis
• Puberty: ↑ Estrogen → duct growth
↑ Progesterone→ lobuloalveolar growth
Permissive role: GH + glucocorticoids + PRL + Insulin.
• Pregnancy: milk secretion doesn’t occur (Inhibition of placental E + P)
Following delivery placental E+P ↓→ lactation begins
165

166. 166
2. Lactation
a. Milk synthesis: initiated during the end of pregnancy/PRL, hPL
b. Lactogenesis: synthesis of milk by alveolar cells & its secretion is
initiated by the loss of placental steroids after birth.
c. Galactopoiesis: maintenance of established lactation, controlled by
PRL
d. Milk ejection: passage of milk from alveolar lumen to the duct system
and collection in the ampulla and larger ducts
delivery to the infant
• Controlled by oxytocin.

167. Relationship of the alveolar lobules and duct system
Arrangement of alveoli in a mammary lobule.
167

168. 3. Milk Ejection Reflex
Nipples (Mechanoreceptors → suckling)
↓
Somatic touch pathways (multisynaptic pathway) induced
↓
Signals sent to Hypothalamic nuclei (SON, PVN)
↓
Oxytocin neurons release oxytocin
↓
Induces contraction of myoepithelial cells that surround alveoli and ducts
↓
Mobilization of milk from the alveoli and duct system
to the nipple
↓
Producing the sensation of ‘milk let-down’ in the mother.
168

169. 3.12.3. Milk Secretion Reflex
Suckling of nipples (mechanoreceptors)
↓
Somatic touch pathways (multisynaptic pathway)
↓
Hypothalamic nuclei
↓
Inhibition of PIH secretion
↓
Secretion of PRL from the anterior pituitary
↓
Stimulation of milk secretion by the mammary glands
169

170. Suckling reflexes
170

171. 171
4. Components of milk
• Protein: casein, α-lactalbumin, β-lactoglobulin
• CHO: lactose, fat, minerals (Ca, Mg, P, Fe).
• Electrolytes: Cl-
, K+
, Na+
…
• Vitamins
• Immunoglobulins: IgMs, IgEs, IgAs
• Growth factors: EGF, IGF-1…

172. 172
5. Lactation and Menstrual Cycle
• Mothers who do not nurse → menses/6 wks after delivery.
• Regular nursing→ amenorrhoeic/25-30wks.
• 50% of the cycles in the first 6 months → anovulatory
6. Lactation as a Contraceptive
a. Suckling →↑ PRL secretion → inhibits GnRH/LHRH secretion.
b. Inhibits the action of GnRH on gonadotropes
c. Antagonizes the action of gns in the ovaries.

173. FEMALE SEXUAL ACT
• Sexual desire is higher during ovulation (may be
due to higher estrogen)
• Like in males effective sexual act depends on both
psychic stimulation and local sexual stimulation
• Local sexual stimulation includes
– Clitoris
– Vulva, vagina, and other perineal regions
173

174. • Sexual sensory signals pudendal nerve
and sacral plexus sacral segments of the
spinal cord cerebrum
• But local integration reflexes in the sacral and
lumbar spinal cord are also responsible for
some of the reactions
174

175. Female Erection and Lubrication
• Controlled by parasympathetic NS
• Identical erectile tissues with the glans penis
extends from introitus up to the clitoris
undergoes similar events like in males
• Vasodilation and accumulation of blood on
these areas tightening of introitus
175

176. • Parasympathetic NS also also the bilateral
Bartholin glands mucus secretion inside
the introitus
• Much lubrication is also provided by mucus
secreted by the vaginal epithelium
176

177. Female Orgasm
• Also called female climax
• Best achieved from both sexual stimulations
• Is analogous to emission and ejaculation in male
• Promote fertilization of ovum
• Resolution – after sometime of the orgasm
177