The process of spermatogenesis occurs in the seminiferous tubules of the testes and involves the formation and maturation of spermatozoa from spermatogonia. It begins at puberty and has five stages: 1) spermatogonial multiplication, 2) growth, 3) first meiotic division, 4) second meiotic division, and 5) spermiogenesis. During spermiogenesis, spermatids undergo morphological changes to become spermatozoa, including condensation of the nucleus and formation of the flagellum. Mature sperm are stored in the epididymis and acquire motility and the ability to fertilize an egg through maturation.

1. SPERMATOGENESIS

2. MALE REPRODUCTIVE SYSTEM
 TESTES
 EPIDIDYMIS
 VAS DEFERENS
 SEMINAL VESICLES
 PROSTATE
 BULBOURETHRAL GLANDS
 URETHRA

3. Male Reproductive System

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SPERMATOGENESIS
• Process of formation
and maturation of
spermatozoa from a
spermatogonia.
• Occurs in the walls of
the seminiferous
tubules of TESTIS.

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 The primitive sex cells
appear earliest in 4th week of
intra uterine life in the wall of
yolk sac as primordial germ
cells
 They migrate to the
developing testes and lie
dormant among the cells
lining the seminiferous
tubules
 At puberty the germ cells
awaken and start the actual
process of spermatogenesis

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SPERMATOGENESIS
• ONSET: Begins at the age of puberty
• Continues through old age
• Extra gonadal origin of primordial germ cells
• STAGES: 5 stages
1. Spermatogonia multiplication
2. Growth
3. 1st Meiotic division
4. 2nd Meiotic division
5. Spermiogenesis

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I. SPERMATOCYTOSIS
• Germ cells multiply by
mitotic division to give a
continuous supply of
spermatogonia
• Two types :
• Type A spermatogonia
• Type B spermatogonia

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• Type A (dark): divides
into Type A (dark) and
Type A (pale).
• Type A (pale):
differentiates into Type B.
• Type B:
differentiates into primary
spermatocyte.

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II. GROWTH
• Type B spermatogonium
enlarges several times
to give rise to the
primary spermatocyte

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III. 1ST MEIOTIC DIVISION
(REDUCTION MEIOSIS)
• Primary spermatocyte
divides into secondary
spermatocyte
• Chromosome number
reduces to half (46 to
23)
• Haploid number of
chromosomes

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IV. 2ND MEIOTIC DIVISION
( EQUATION MEIOSIS)
• Secondary spermatocyte
divides to form
spermatids.
• Reduction in size. No
reduction in number of
chromosomes.
• Maintains haploid no. of
chromosomes.

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V. SPERMIOGENESIS
(SPERMATELEOSIS)
• Each spermatid
undergoes
metamorphic
changes to
become a
spermatozoon/
sperm.

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CHANGES DURING SPERMIOGENESIS
• Each spermatid possesses:
• Golgi apparatus
• A spherical nucleus
• Two centrioles
• Numerous mitochondria
• Abundant cytoplasm

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CHANGES DURING SPERMIOGENESIS
1. Golgi apparatus spreads
over the ant. pole of
nucleus, forms
acrosomic cap.
2. Centrioles occupies the
post. pole of nucleus,
gives rise to axial
filament/ flagellum

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CHANGES DURING SPERMIOGENESIS
3. Mitochondria
aggregates in the
middle in a spiral
manner, forms the
mitochondrial
sheath of middle
piece.
4. Nucleus constitutes
the head of sperm.

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CHANGES DURING SPERMIOGENESIS
5. The spermatid
elongates
6. Most of the
cytoplasm extruded
as residual bodies.
7. Cell membrane
persists as covering
of the sperm

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21

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STRUCTURE OF SPERM
1. HEAD
2. NECK
3. BODY/ MIDDLE
PIECE
4. TAIL/ PRINCIPAL
PIECE

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HEAD
• Contains the nucleus
with 23 chromosomes
(haploid)
• Ovoid shape
• Overlapped by
acrosomal cap
• Entire head enveloped
by cell membrane

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NECK
• Narrow.
• Has a funnel shaped
basal body (connecting
piece)
• Contains the centriole.

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BODY (MIDDLE PIECE)
• Long, cylindrical
• Consists of axial
filament in the
centre, surrounded
by mitochondrial
sheath
• A ring centriole
(annulus) situated at
the junction of body
and tail.

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TAIL (PRINCIPAL PIECE)
• Long, flagellum-like
• Axial filament continues
from the body into the tail.
• Surrounded by a fibrous
sheath.
• Terminal portion where
fibrous sheath is absent –
end piece.

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• Axial filament :
• A pair of central
fibrils
• 9 pairs of fibrils
arranged around the
central pair.

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• Spermatazoon produced in the seminiferous
tubule are:
• Immature
• Non-motile
• Incapable of fertilizing an ovum
• These immature sperm are carried to the
epididymis

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MATURATION
• Maturation process takes
place in epididymis
• Changes in the
glycoproteins of plasma
memb. covering the head.
• Sperm acquire motility

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CAPACITATION
• Final step of
maturation.
• Ability to fertilize an
ovum is called
capacitation.
• Sperm acquires this
ability within the
female genital tract.

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ACROSOMAL REACTION
1
2
3
4 5
6
1. Head of the sperm contacts the jelly coat of the egg
- triggers the release of hydrolytic enzymes which
dissolve the jelly coat and starts the acrosomal
reaction

33. ABNORMAL SPERMS
They are with:
Two heads
Two tails
Dwarf
Giant
Contrary to oocytes
abnormal sperms are
seen more frequently

34. PROSTATE GLAND
•Prostate is a single, midline
gland just inferior to urinary
bladder.
•Prostate secretions:
•Fructose
•PROSTAGLANDINS –
promote uterine
contractions to help facilitate
sperm movement up uterus
into fallopian tubes.
SEMINAL VESICLE
•Plastered up against the
dorsal side of urinary bladder.
• provide secretions that make
up most of seminal fluid.
•Fluid lubricates path of exiting
sperm.
•Secretions slightly alkaline –
helps to neutralize slightly
acidic environment of vagina.

35. ACCESSORY GLANDS
• Seminal vesicles
• Empty into ejaculatory duct
• Produce about 60% of semen
• Secretion contains fibrinogen
• High pH
• Prostate gland
• Produces about 30% of semen
• Thin, milky secretion, high pH
• Contain clotting factors, and fibrinolysin
• Bulbourethral glands
• Contribute about 5% to semen
• Mucous secretion. Just before ejaculation
• Helps neutralize pH of female vagina

36. SEMEN OR SEMINAL FLUID
• 2-5 mL of fluid expelled, Mixture of sperm and seminal fluid
• 60% seminal vesicle fluid, 30% prostatic, 10% sperm
• normal sperm count 50-120 million/mL
• Provides transport medium, nutrients
components of semen
• fructose - energy for sperm motility
• fibrinogen causes clotting
• enzymes convert fibrinogen to fibrin
• fibrinolysin liquefies semen within 30 minutes
• prostaglandins stimulate female peristaltic contractions
• spermine is a base stabilizing sperm pH at 7.2 to 7.6

37. Vasectomy

38. NORMAL ABNORMAL

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POINTS TO REMEMBER
• Time taken for spermatogonia to convert into a
spermatozoa : 64 days.
• A single ejaculation usually contains: 200-300 million
sperms.
• Degeneration time of sperm:
• 48 hours after ejaculation