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![Function of Female Reproductive
System
Produce sex hormones
Produce functioning gamates [ova]
Support & protect developing embryo](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-4-320.jpg)
![General Physical Changes
Axillary & pubic hair growth
Changes in body conformation [widening
of hips, development of breasts]
Onset of first menstrual period
[menarche]
Mental changes](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-5-320.jpg)
![Major Organs
Ovaries [ gonads]
Uterine tubes [ fallopian tubes]
Uterus
Vagina
Accessory glands
External genitalia
Breasts](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-6-320.jpg)
![fallopian tubes [uterine tubes]
stretch from the uterus to the ovaries and
measure about 8 to 13 cm in length.
range in width from about one inch at the end
next to the ovary, to the diameter of a strand of
thin spaghetti.
The ends of the fallopian tubes lying next to the
ovaries feather into ends called fimbria
Millions of tiny hair-like cilia line the fimbria and
interior of the fallopian tubes. The cilia beat in
waves hundreds of times a second catching the
egg at ovulation and moving it through the tube
to the uterine cavity.
Fertilization typically occurs in the fallopian tube](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-11-320.jpg)
![Mammary Glands [ breasts]
Present in both sexes - normally only functional in
females
Developmentally they are derived from sweat glands
Contained within a rounded skin-covered breast anterior
to the pectoral muscles of the thorax
Slightly below center of each breast is a ring of pigmented
skin, the areola - this surrounds a central protruding
nipple
Internally - they consist of 15 to 25 lobes that radiate
around and open at the nipple
Each lobe is composed of smaller lobules- these contain
alveoli that produce milk when a women is lactating
non-pregnant women - glandular structure is undeveloped
- hence breast size is largely due to the amount of fat
deposits](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-24-320.jpg)
![Erection
Involves increase in length, width &
firmness
Changes in blood supply: arterioles dilate,
veins constrict
The spongy erectile tissue fills with blood
Erectile Dysfunction [ED] also known as
impotence](https://image.slidesharecdn.com/femalereproductivesystemjonathan-160228233247/85/Female-reproductive-system-jonathan-56-320.jpg)
More Related Content
Similar to Female reproductive system jonathan
Female reproductive system jonathan
- 1.
- 2.
- 3. Adolescence Puberty Burstof hormones activate maturation of the gonads: ovaries Begins: 8-13 yrs of age Abnormally early = precocious puberty Delayed =Primary Amenorrhea
- 4. Function of FemaleReproductive System Produce sex hormones Produce functioning gamates [ova] Support & protect developing embryo
- 5. General Physical Changes Axillary & pubic hair growth Changes in body conformation [widening of hips, development of breasts] Onset of first menstrual period [menarche] Mental changes
- 6. Major Organs Ovaries[ gonads] Uterine tubes [ fallopian tubes] Uterus Vagina Accessory glands External genitalia Breasts
- 7. ovaries Each ovaryis about the size and shape of an almond. In young women the ovaries are about 1½ - 2 inches long, 1 inch wide & 1/3 inch thick. After menopause they tend to shrink. they produce eggs (also called ova) every female is born with a lifetime supply of eggs they also produce hormones: Estrogen & Progesterone Male Homolog = testes
- 9. oogenesis when thegirl becomes sexually mature, the primary oocytes recommence their development, usually one at a time and once a month. The primary oocyte grows much larger and completes the meiosis I, forming a large secondary oocyte and a small polar body that receives little more than one set of chromosomes.
- 10. oogenesis In humans(and most vertebrates), the first polar body does not go on to meiosis II, but the secondary oocyte does proceed as far as metaphase of meiosis II and then stops. Only if fertilization occurs will meiosis II ever be completed. Entry of the sperm restarts the cell cycle
- 11. fallopian tubes [uterinetubes] stretch from the uterus to the ovaries and measure about 8 to 13 cm in length. range in width from about one inch at the end next to the ovary, to the diameter of a strand of thin spaghetti. The ends of the fallopian tubes lying next to the ovaries feather into ends called fimbria Millions of tiny hair-like cilia line the fimbria and interior of the fallopian tubes. The cilia beat in waves hundreds of times a second catching the egg at ovulation and moving it through the tube to the uterine cavity. Fertilization typically occurs in the fallopian tube
- 13. uterus pear-shaped muscularorgan in the upper female reproductive tract. The fundus is the upper portion of the uterus where pregnancy occurs. The cervix is the lower portion of the uterus that connects with the vagina and serves as a sphincter to keep the uterus closed during pregnancy until it is time to deliver a baby. the uterus expands considerably during the reproductive process. the organ grows to from 10 to 20 times its normal size during pregnancy.
- 15. endometrium Functional zone– layer closest to the cavity – contains majority of glands. Thicker portion – undergoes changes with monthly cycle Basal zone – layer just under myometrium, attaches functional layer to myometrial tissue, has terminal ends of glands. Remains constant
- 16. Uterine arteries Arcuatearteries - encircle endometrium Radial arteries – connect arcuate to straight Straight arteries – deliver blood to basilar zone Spiral arteries – deliver blood to functional zone
- 17. The Cervix thelower portion or neck of the uterus. The cervix is lined with mucus, the quality and quantity of which is governed by monthly fluctuations in the levels of the estrogen and progesterone. When estrogen levels are low, the mucus tends to be thick and sparse, hindering sperm from reaching the fallopian tubes. But when an egg is ready for fertilization, estrogen levels are high, the mucus then becomes thin and slippery, offering a “friendly environment” to sperm at the end of pregnancy, the cervix acts as the passage through which the baby exits the uterus into the vagina. The cervical canal expands to roughly 50 times its normal width in order to accommodate the passage of the baby during birth
- 18. The Vagina vagin= sheath a muscular, ridged sheath connecting the external genitals to the uterus. functions as a two-way street, accepting the penis and sperm during intercourse and roughly nine months later, serving as the avenue of birth through which the new baby enters the world
- 21. External genetalia vulva—whichruns from the pubic area downward to the rectum. Mons pubis or "mound of Venus" is the V-shaped area covered with hair Labia majora or "greater lips" are the part around the vagina containing two glands (Bartholin’s glands)which helps lubrication during intercourse. Male Homolog = scrotum Labia minora or "lesser lips" are the thin hairless ridges at the entrance of the vagina, which joins behind and in front. In front they split to enclose the clitoris The clitoris is a small pea-shaped structure (equivalent to penis in males ) It plays an important part in sexual excitement in females. Male Homolog = penis
- 22. External genetalia Theurethral orifice or external urinary opening is below the clitoris on the upper wall of the vagina and is the passage for urine The introitus or opening of the vagina is separate from the urinary opening (unlike males) and located below it. The hymen is a thin cresentic fold of tissue which partially covers the opening of the vagina. medically it is no longer considered to be a 100% proof of female virginity.
- 24. Mammary Glands [breasts] Present in both sexes - normally only functional in females Developmentally they are derived from sweat glands Contained within a rounded skin-covered breast anterior to the pectoral muscles of the thorax Slightly below center of each breast is a ring of pigmented skin, the areola - this surrounds a central protruding nipple Internally - they consist of 15 to 25 lobes that radiate around and open at the nipple Each lobe is composed of smaller lobules- these contain alveoli that produce milk when a women is lactating non-pregnant women - glandular structure is undeveloped - hence breast size is largely due to the amount of fat deposits
- 26. glands Lesser Vestibular(Paraurethral, Skene's) Male Homolog = prostate located on the upper wall of the vagina, around the lower end of the urethra. They drain into the urethra and near the urethral opening Function - mucus production to aid lubrication during intercourse Greater Vestibular (Bartholin's) Male Homolog = bulbourethral glands located slightly below and to the left and right of the opening of the vagina. They secrete mucus to provide lubrication, especially when the woman is sexually aroused
- 27. Table 1. ProductionRate of Sex Steroids in Women at Different Stages of the Menstrual Cycle DAILY PRODUCTION RATE SEX STEROIDS* Early Follicular Preovulatory Midluteal Progesterone (mg) 1 4 25 17-Hydroxyprogesterone (mg) 0.5 4 4 Dehydroepiandrosterone (mg) 7 7 7 Androstenedione (mg) 2.6 4.7 3.4 Testosterone (µg) 144 171 126 Estrone (µg) 50 350 250 Estradiol (µg) 36 380 250 From Baird DT. Fraser IS. Blood production and ovarian secretion rates of esuadiol-17β and estrone in women throughout the menstrual cycle. J Clin Endocri-nol Metab 38: l009-1017. 1974. @ The Endocrine Society. *Values are expressed in milligrams or micrograms per 24 hours.
- 28. The female hormonesthat control the cyclic growth and shedding of the endometrium are estrogen and progesterone. Estrogen and progesterone are produced by the ovaries. Estrogen causes the growth or proliferation of the endometrium during the first 2 weeks of the menstrual cycle. After ovulation, the ovary produces progesterone. Hormones and the menstrual cycle
- 33.
- 34. Adolescence Puberty Burstof hormones activate maturation of the gonads: testes Begins: 9 – 14 yrs of age Abnormally early = precocious puberty Delayed = eunuchoidism
- 35. General Physical Changes Enlargement of the external and internal genitalia Voice changes Hair growth Mental changes Changes in body conformation and skin Sebaceous gland secretions thicken/increase acne
- 36. External Genitalia Gonads= testes undescended by birth= cryptorchidsim Scrotum Penis
- 37. Testes Each testisis an oval structure about 5 cm long and 3 cm in diameter Covered by: tunica albuginea Located in the scrotum There are about 250 lobules in each testis. Each contains 1 to 4 -seminiferous tubules that converge to form a single straight tubule, which leads into the rete testis. Short efferent ducts exit the testes. Interstitial cells (cells of Leydig), which produce male sex hormones, are located between the seminiferous tubules within a lobule.
- 40. scrotum consists ofskin and subcutaneous tissue A vertical septum, of subcutaneous tissue in the center divides it into two parts, each containing one testis. Smooth muscle fibers, called the dartos muscle, in the subcutaneous tissue contract to give the scrotum its wrinkled appearance. When these fibers are relaxed, the scrotum is smooth. the cremaster muscle, consists of skeletal muscle fibers and controls the position of the scrotum and testes. When it is cold or a man is sexually aroused, this muscle contracts to pull the testes closer to the body for warmth.
- 42. Epididymis a longtube (about 6 meters) located along the superior and posterior margins of the testes. Sperm that leave the testes are immature and incapable of fertilizing ova. They complete their maturation process and become fertile as they move through the epididymis. Mature sperm are stored in the lower portion, or tail, of the epididymis
- 43. spermatic cord containsthe proximal ductus deferens, testicular artery and veins, lymph vessels, testicular nerve, cremaster muscle and a connective tissue covering.
- 44. Ejaculatory Duct Eachductus deferens, at the ampulla, joins the duct from the adjacent seminal vesicle (one of the accessory glands) to form a short ejaculatory duct. Each ejaculatory duct passes through the prostate gland and empties into the urethra.
- 46. Urethra extends fromthe urinary bladder to the external urethral orifice at the tip of the penis. It is a passageway for sperm and fluids from the reproductive system and urine from the urinary system. divided into three regions: The prostatic urethra, the membranous urethra & the penile urethra (also called spongy urethra or cavernous urethra)
- 47. accessory glands arethe seminal vesicles, prostate gland, and the bulbourethral glands. These glands secrete fluids that enter the urethra.
- 48. Seminal Vesicles glandsposterior to the urinary bladder. Each has a short duct that joins with the ductus deferens at the ampulla to form an ejaculatory duct, which then empties into the urethra. The fluid is viscous and contains fructose, prostaglandins and proteins.
- 49. Prostate a firm,dense structure about the size of a walnut that is located just inferior to the urinary bladder. encircles the urethra as it leaves the urinary bladder. Numerous short ducts from the prostate gland empty into the prostatic urethra. The secretions of the prostate are thin, milky colored, and alkaline. They function to enhance the motility of the sperm.
- 50. Bulbourethral Glands (Cowper's) small, about the size of a pea, and located near the base of the penis. A short duct from each enters the proximal end of the penile urethra. In response to sexual stimulation, the bulbourethral glands secrete an alkaline mucus-like fluid
- 52. Seminal Fluid orSemen a slightly alkaline mixture of sperm cells and secretions from the accessory glands. Secretions from the seminal vesicles make up about 60 percent of the volume of the semen, with most of the remainder coming from the prostate gland. The sperm and secretions from the bulbourethral gland contribute only a small volume. The volume of semen in a single ejaculation may vary from 1.5 to 6.0 ml. There are between 50 to 150 million sperm per milliliter of semen. Sperm counts below 10 to 20 million per milliliter usually present fertility problems.
- 53. penis is acylindrical pendant organ located anterior to the scrotum and functions to transfer sperm to the vagina. consists of three columns of erectile tissue that are wrapped in connective tissue and covered with skin. The two dorsal columns are the corpora cavernosa. The single, midline ventral column surrounds the urethra and is called the corpus spongiosum.
- 54. penis 3 parts:a root, body (shaft), and glans penis. The root of the penis attaches it to the pubic arch the body is the visible, pendant portion. The corpus spongiosum expands at the distal end to form the glans penis. The urethra, which extends throughout the length of the corpus spongiosum, opens through the external urethral orifice at the tip of the glans penis. A loose fold of skin, called the prepuce, or foreskin, covers the glans penis.
- 56. Erection Involves increasein length, width & firmness Changes in blood supply: arterioles dilate, veins constrict The spongy erectile tissue fills with blood Erectile Dysfunction [ED] also known as impotence
- 57. Hormones Follicle-stimulating hormone(FSH) stimulates spermatogenesis Interstitial Cell Stimulating Hormone (ICSH) stimulates the production of testosterone testosterone stimulates the development of male secondary sex characteristics & spermatogenesis.
- 59. Spermatogenesis Sperm areproduced within the seminiferous tubules. Interspersed within the tubules are large cells which are the sustentacular cells (Sertoli's cells), which support and nourish the other cells.
- 60. Spermatogenesis Each primaryspermatocytes goes through the first meiotic division, meiosis I, to produce two secondary spermatocytes, each with 23 chromosomes (haploid). Just prior to this division, the genetic material is replicated During meiosis I, one chromosome, goes to each secondary spermatocyte. In the second meiotic division, meiosis II, each secondary spermatocyte divides to produce two spermatids. There is no replication of genetic material in this division, but a single-stranded chromatid goes to each cell. As a result of the two meiotic divisions, each primary spermatocyte produces four spermatids. each spermatid has 23 chromosomes (haploid), one from each pair in the original primary spermatocyte.
- 62. Spermatogenesis The finalstep in the development the spermatids formed from spermatogenesis become mature spermatozoa, or sperm. The mature sperm cell has a head, midpiece, and tail. The head, also called the nuclear region, contains the 23 chromosomes surrounded by a nuclear membrane. The tip of the head is covered by an acrosome, which contains enzymes that help the sperm penetrate the female gamete. The midpiece, metabolic region, contains mitochondria that provide adenosine triphosphate (ATP). The tail, locomotor region, uses a typical flagellum for locomotion.
- 65. Spermatogenesis The spermare released into the lumen of the seminiferous tubule and leave the testes. They then enter the epididymis where they undergo their final maturation and become capable of fertilizing a female gamete. Sperm production begins at puberty and continues throughout the life of a male. The entire process, beginning with a primary spermatocyte, takes about 74 days. After ejaculation, the sperm can live for about 48 hours in the female reproductive tract.
Editor's Notes
- #8 They are among the first organs to be formed as a female baby develops in the uterus. At the 20-week mark, the structures that will become the ovaries house roughly 6 to 7 million potential egg cells. From that point on, the number begins to decrease rapidly. A newborn infant has between 1 million to 2 million egg cells. By puberty the number has plummeted to 300,000. For every egg that matures and undergoes ovulation, roughly a thousand will fail, so that by menopause, only a few thousand remain. During the course of an average reproductive lifespan, roughly 300 mature eggs are produced for potential conception. The ovaries produce these hormones throughout the fertile period of a woman's life. It is the hormones that control the menstrual cycle. As you get older and menopause approaches, the ovaries make less and less of these hormones and the periods eventually stop altogether. So the normal ovaries cannot usually be felt in a clinical examination except in young, thin women. The ovaries are the main source of female hormones (estrogen and progesterone). These hormones control the development of female body characteristics, such as the breasts, body shape, and body hair. They also regulate the menstrual cycle and pregnancy. What is estrogen? Estrogen is a group of female sex hormones that stimulate the appearance of secondary female sex characteristics in girls at puberty. Estrogen controls controls the growth of the lining of the uterus during the first part of the menstrual cycle, cause breast development in pregnancy and regulates various metabolic processes.
- #10 Which chromosomes end up in the egg and which in the polar body is entirely a matter of chance.
- #12 (4 to 6 inches) = length called fimbria (Latin for "fringes" or "fingers").each tube has about about 20 to 25 Millions of tiny hair-like cilia line the fimbria and interior of the fallopian tubes. The cilia beat in waves hundreds of times a second catching the egg at ovulation and moving it through the tube to the uterine cavity. Other cells in the tube's inner lining or endothelium nourish the egg and lubricate it's path during its stay inside the fallopian tube. Once inside the fallopian tube, the egg and sperm meet and the egg is fertilized. If an egg doesn't become fertilized within 24 to 36 hours after ovulation, it will deteriorate and be removed by the body's immune system like any other dead cell in the body.
- #14 Size = 3 in long x2 inch diameter Weighs about 1-1.5 oz Pregnancy – watermelon sized
- #15 Each month the uterus goes through a cyclical change, first building up its endometrium or inner lining to receive a fertilized egg, then, if conception does not occur, shedding the unused tissue through the vagina in the monthly process called menstruation
- #18 The vagina ends at the cervix, (cervical mucus changes: employed by birth control pills, shots and implants. One of the ways they prevent conception is to render the cervical mucus thick, sparse, and hostile to sperm.)
- #23 It was thought to be proof of virginity as it is broken after the first sexual intercourse. However it is stretchable, and may break due to vigorous exercises, cycling, gymnastics or tampon use.Therefore
- #25 Large sebaceous glands in the areola make it slightly bumpy & produce sebum that reduces chapping and cracking of the skin of the nipple Autonomic NS controls smooth muscle fibers in the areola and nipple cause the nipple to become erect when stimulated by tactile or sexual stimuli & when exposed to the cold Lobes are padded & separated from each other by fibrous connective tissue and fat The connective tissue forms suspensory ligaments that attach the breast to the underlying muscle fascia
- #29 Progesterone causes the endometrial glands to secrete nutritive substances required by the embryo and to allow it to implant into the endometrial lining. If fertilization and implantation do not occur, the progesterone falls and the endometrial lining is sloughed off - resulting in menstrual bleeding. If fertilization and implantation do occur, then the ovary continues producing progesterone and the endometrium remains intact to support embryo development and pregnancy.After ovulation, in the space where the egg used to be, a second small cystic area known as the corpus luteum develops and begins to secrete progesterone. The corpus luteum eventually gets reabsorbed by the ovary.
- #31 Once a mature egg has begun its trip through the fallopian tube, remnants of the winning follicle form the corpus luteum, or “yellow body.” Progesterone from the corpus luteum halts development of the remaining follicles and brings the lining of the uterus to peak preparedness. Meanwhile, the follicle that held the egg still has a critical role to play. First it shrinks markedly, then begins to accumulate fatty substances, or lipids, that give it a yellowish tinge. The resulting structure, now called the corpus luteum (yellow body), produces progesterone and estradiol, two of the hormones critical to reproduction. In a non-pregnant woman, the corpus luteum lasts for about 14 days, after which it shrinks and dries up, eventually becoming a speck of fibrous scar tissue. If conception occurs, however, a hormone from the developing placenta, which surrounds the baby in the uterus, stimulates the corpus luteum to maintain its production of progesterone during the first trimester of pregnancy
- #35 period when the endocrine and gamete – producing functions of the gonads have first developed to where reproduction is possible
- #38 the tunica albuginea, surrounds each testis and extends inward to form septa that partition the organ into lobules There are about 250 lobules in each testis. Each contains 1 to 4 highly coiled seminiferous tubules that converge to form a single straight tubule, which leads into the rete testis. Short efferent ducts exit the testes. Interstitial cells (cells of Leydig), which produce male sex hormones, are located between the seminiferous tubules within a lobule
- #41 A vertical septum, or partition, of subcutaneous tissue in the center divides it into two parts, each containing one testis. Smooth muscle fibers, called the dartos muscle, in the subcutaneous tissue contract to give the scrotum its wrinkled appearance. When these fibers are relaxed, the scrotum is smooth. the cremaster muscle, consists of skeletal muscle fibers and controls the position of the scrotum and testes. When it is cold or a man is sexually aroused, this muscle contracts to pull the testes closer to the body for warmth
- #43 a long tube (about 6 meters) that is tightly coiled to form a comma-shaped organ located along the superior and posterior margins of the testes. Sperm that leave the testes are immature and incapable of fertilizing ova. They complete their maturation process and become fertile as they move through the epididymis. Mature sperm are stored in the lower portion, or tail, of the epididymis
- #47 It is a passageway for sperm and fluids from the reproductive system and urine from the urinary system. While reproductive fluids are passing through the urethra, sphincters contract tightly to keep urine from entering the urethra.
- #49 saccular glands posterior to the urinary bladder. Each gland has a short duct that joins with the ductus deferens at the ampulla to form an ejaculatory duct, which then empties into the urethra. The fluid is viscous and contains fructose, which provides an energy source for the sperm; prostaglandins, which contribute to the mobility and viability of the sperm; and proteins that cause slight coagulation reactions in the semen after ejaculation.
- #50 a firm, dense structure that is located just inferior to the urinary bladder. It is about the size of a walnut and encircles the urethra as it leaves the urinary bladder. Numerous short ducts from the substance of the prostate gland empty into the prostatic urethra. The secretions of the prostate are thin, milky colored, and alkaline. They function to enhance the motility of the sperm.
- #51 small, about the size of a pea, and located near the base of the penis. A short duct from each gland enters the proximal end of the penile urethra. In response to sexual stimulation, the bulbourethral glands secrete an alkaline mucus-like fluid. This fluid neutralizes the acidity of the urine residue in the urethra, helps to neutralize the acidity of the vagina, and provides some lubrication for the tip of the penis during intercourse.
- #53 a slightly alkaline mixture of sperm cells and secretions from the accessory glands. Secretions from the seminal vesicles make up about 60 percent of the volume of the semen, with most of the remainder coming from the prostate gland. The sperm and secretions from the bulbourethral gland contribute only a small volume. The volume of semen in a single ejaculation may vary from 1.5 to 6.0 ml. There are between 50 to 150 million sperm per milliliter of semen. Sperm counts below 10 to 20 million per milliliter usually present fertility problems. Although only one sperm actually penetrates and fertilizes the ovum, it takes several million sperm in an ejaculation to ensure that fertilization will take place.
- #54 the male copulatory organ, is a cylindrical pendant organ located anterior to the scrotum and functions to transfer sperm to the vagina. consists of three columns of erectile tissue that are wrapped in connective tissue and covered with skin. The two dorsal columns are the corpora cavernosa. The single, midline ventral column surrounds the urethra and is called the corpus spongiosum.
- #57 spongy erectile tissue is a loose network of connective tissue with many spaces ED – inability to achieve or maintain an erection Affects approx. 30 mil men in USA. Not unusual to experience sometime – usually due to psychological problems: stress, depression, worrying, grief Physical problems: nerve damage – usually accompanying diabetes or alcoholism Atherosclerosis [fatty deposits] in arteries supplying penis medications: HTN, antihistamines, antinausea & antiseizure, antidepressants, sedatives, tranquilzers Cigarettes, marijuana & alcohol Treat ED – eliminate problem. Medications: Viagra type enhance nitric oxide that is released with arousal and caused arterioles to dilate
- #60 Sperm are produced within the seminiferous tubules. A transverse section of a seminiferous tubule shows that it is packed with cells in various stages of development. Interspersed with these cells, there are large cells that extend from the periphery of the tubule to the lumen. These large cells are the supporting, or sustentacular cells (Sertoli's cells), which support and nourish the other cells
- #61 Each primary spermatocytes goes through the first meiotic division, meiosis I, to produce two secondary spermatocytes, each with 23 chromosomes (haploid). Just prior to this division, the genetic material is replicated so that each chromosome consists of two strands, called chromatids, that are joined by a centromere. During meiosis I, one chromosome, consisting of two chromatids, goes to each secondary spermatocyte. In the second meiotic division, meiosis II, each secondary spermatocyte divides to produce two spermatids. There is no replication of genetic material in this division, but the centromere divides so that a single-stranded chromatid goes to each cell. As a result of the two meiotic divisions, each primary spermatocyte produces four spermatids. During spermatogenesis there are two cellular divisions, but only one replication of DNA so that each spermatid has 23 chromosomes (haploid), one from each pair in the original primary spermatocyte. Each successive stage in spermatogenesis is pushed toward the center of the tubule so that the more immature cells are at the periphery and the more differentiated cells are nearer the center.
- #63 The final step in the development of sperm is called spermiogenesis. In this process, the spermatids formed from spermatogenesis become mature spermatozoa, or sperm. The mature sperm cell has a head, midpiece, and tail. The head, also called the nuclear region, contains the 23 chromosomes surrounded by a nuclear membrane. The tip of the head is covered by an acrosome, which contains enzymes that help the sperm penetrate the female gamete. The midpiece, metabolic region, contains mitochondria that provide adenosine triphosphate (ATP). The tail, locomotor region, uses a typical flagellum for locomotion. The sperm are released into the lumen of the seminiferous tubule and leave the testes. They then enter the epididymis where they undergo their final maturation and become capable of fertilizing a female gamete. Sperm production begins at puberty and continues throughout the life of a male. The entire process, beginning with a primary spermatocyte, takes about 74 days. After ejaculation, the sperm can live for about 48 hours in the female reproductive tract.