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Reproduction

1. The Highlights

2. The Male Reproductive System

3. Testes
- produce sperm cells
developed from germ cells in seminiferous
tubule
- secret testosterone by interstitial (Leydig)
cells

4. sperm
testosterone

5. Scrotum
protect testes
and maintain the
temperature of
the testes 2
degrees lower
than body
temperature.

6. Epididymus
the storage site of sperm cells. It absorbs
about 90% of the fluid secreted by the testis.
Sperm remain stored here for 40-60 days and are
absorbed if not ejaculated prior to that time.

9. The fluid
expelled during
orgasm
Mixture of
secretion from
epididymis,
seminal vesicle,
prostate, and
bulbourethral
gland.
Semen (seminal fluid )

10. Major constituents of semen
• Sperm
• Fructose
• Clotting and anticoagulant
factors
• Prostaglandins
• Spermine

11. produce ATP for
sperm motility.
enzymes used to
dissolve a path to
penetrate the egg
gene

12. Sperm cells from epididymis are
present at a count of 50-120 million
sperm/mL.
Sperm count decreased from 113
million sperm/mL in 1940 to 66 million
sperm/mL in 1990. Semen volume
dropped by 19%.
< 20-25 million/ml = infertility (sterility)

13. Fructose
produced by the
seminal vesicles
provides a source of
energy for the sperm.

14. Clotting and
anticoagulant
factors
produced by seminal
vesicles and
prostate.
Semen clots like
blood.
About 15-30 minutes
later, anticoagulant
factors dissolve the
clot.

15. Prostaglandins
produced by the
prostate and seminal
vesicles,
stimulate peristaltic
contractions of the
female reproductive
tract that may help
draw semen into the
uterus.

16. Spermine
is a base that
reduces acidity of
the female
vagina,
increasing the
survival rate of
sperm.

17. Male Sexual
Response
1)erection of the
penis,
allowing it to
penetrate the
female vagina
2)ejaculation,
expelling
semen into
the vagina.

18. Ejaculation
Initiated by sympathetic
nerve impulses
The ducts and
accessory glands
contract, emptying their
contents into the
urethra.
The urethral sphincters
constrict.
The bulbospongiosus
muscles of the penis
contract rapidly and
rhythmically, propelling
semen from the urethra.

19. Fate of sperm cells
capacitated (test tube?)
viable for 2 days (egg: 12-24 hr)
Only ~ 100 reach the
destination.
Only one sperm fertilizes the
egg.

20. Refractory Period
A period following
ejaculation and lasting
anywhere from 10
minutes to a few hours
impossible to attain
another erection and
orgasm

21. Semen analysis
Motility>60% should be motile with in 3hrs of
collection.
Count >40 million /ml is normal.
Liquify-should liquify with in half an hour.
Morphology->80% should have normal
morphology

22. The Male Reproductive System in Midsagital
View
Figure 28.1

23. MALE REPRODUCTIVE SYSTEM
 TESTIS
- thick connective tissue capsule
- connective tissue septa divide
testis into 250 lobules
TUNICA ALBUGINEA
(1) SEMINIFEROUS TUBULES
- each lobule contains 1-4
seminiferous tubules and
interstitial connective tissue
- produce sperm
INTERSTITIAL TISSUE
- contains Leydig cells which
produce testosterone
(2) RECTUS TUBULES
(3) RETE TESTIS
(4) EFFERENT DUCTULES
(5) EPIDIDYMIS

24. MALE REPRODUCTIVE SYSTEM
SERTOLI
CELLS
SPERMATOGONIA
1º SPERMATOCYTE
2º SPERMATOCYTE
SPERMATIDS
 SPERMATOGENESIS
SPERMATOGONIA 1º SPERMATOCYTE 2º SPERMATOCYTE SPERMATIDS
SERTOLI CELLS:
- columnar with adjoining lateral processes
- Sertoli-Sertoli junctions divide
seminiferous tubules into basal and
adluminal compartments
- extend from basal lamina to lumen

25. Basal Lamina
2n 2nSpermatogonia (stem cells)
2nmitosis
Daughter cell Type A
spermatogonium
remain at basal lamina
as a precursor cell
Daughter cell Type B Spermatagonium
Moves to adluminal compartment
n
n 1° spermatocyte
n
Meiosis I completed
2° spermatocyte
n n n n
Early spermatids
n n n nLate spermatids
Meiosis II

26. MALE REPRODUCTIVE SYSTEM
 SPERMATOGENESIS
THREE PHASES:
(1) Spermatogonial Phase (Mitosis)
(2) Spermatocyte Phase (Meiosis)
(3) Spermatid Phase (Spermiogenesis)
- acrosome formation; golgi granules fuse to
form acrosome that contains hydrolytic
enzymes which will enable the
spermatozoa to move through the
investing layers of the oocyte
- flagellum formation; centrioles and
associate axoneme (arrangement of
microtubules in cilia)
- changes in size and shape of nucleus;
chromatin condenses and shedding of
residual body (cytoplasm)

27. MALE REPRODUCTIVE SYSTEM
 HORMONAL REGULATION OF
MALE REPRODUCTIVE FUNCTION
HYPOTHALAMUS REGULATES ACTIVITY OF
ANTERIOR PITUITARY (ADENOHYPOPHYSIS)
ADENOHYPOPHYSIS SYNTHESIZES HORMONES
(LH and FSH) THAT MODULATE ACTIVITY OF
SERTOLI AND LEYDIG CELLS
Luteinizing Hormone (LH): stimulates testosterone
production by Leydig cells
Follicle Stimulating Hormone (FSH): stimulates production of sperm
in conjunction with testosterone by regulating activity of Sertoli cells
SERTOLI CELLS STIMULATED BY FSH AND TESTOSTERONE RELEASE
ANDROGEN BINDING PROTEIN WHICH BINDS TESTOSTERONE;
THEREBY INCREASING TESTOSTERONE CONCENTRATION WITHIN THE
SEMINIFEROUS TUBULES AND STIMULATING SPERMATOGENESIS

29. SPERMATOGENESIS
DEFINITION: The development and maturation
of spermatozoa is called spermatogenesis. It
consists of two parts
Spermatocytogenesis.
 Spermiogenesis.

30. The sperm formation involves two steps : in the
first step spermatogenic cells form rounded cells
called spermatids which in the second step
differentiate into specialized cells known as
sperms. These processes are labeled respectively
as
 Spermatocytogenesis
Spermiogenesis

31. Site of sperm formation
Seminiferous tubules of Testis

33. Spermatocytogenesis
The primitive sex cells
appear earliest in 4
th
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

34. Spermatocytogenesis
At puberty the germ cells
awaken and start the actual
process of spermato genesis
These cells increase in number
by simple mitosis to form cells
known as spermatogonia ;
type- A and type- B.
Type-B spermatogonia,
replicate DNA to have 46 double
structured chromosomes to
begin meiosis-1 and are called
primary spermatocytes.

37. Spermatocytogenesis (cont.)
As steps of
spermatogenesis continue
the spermatocytes
progressively move from
basement membrane to
the luminal side of
seminiferous tubule
The cells of Sertoli
provide nutrition and
pockets of support to
developing spermatocytes

38. Spermatocytogenesis (cont.)
The spermatocytes in
different stages of
development remain
attached by
cytoplasmic bridges
All the spermatocytes
are not in the same
stage of development
in the seminiferous
tubules

39. SPERMIOGENESIS
Transformation of spermatids into a
tailed,motile spermatozoa is called
spermiogenesis.
Spermatozoa are mature germ cells,haploid and
posses a -
Head
Middlepiece
Tail .

40. About 512 spermatozoa develop from a single
spermatozoa.

41. SPERMIOGENESIS
Spermatids are rounded
cells.
They modify to assume
specific shape of the sperm.
This process is called
Spermiogenesis. In it they
elongate and reorganize
internal structure to
acquire the particular
shape.

42. SPERMIOGENESIS (Cont.)
The changes include ;
1.Golgi apparatus forms
acrosomal cap-proteolytic
enzymes
2.Nucleus is condensed
3.Centrioles: make collar
around neck
4.Microtubules, form flagellum,
5.Mitochondria arrange as
spiral around neck
Excess cytoplasm cast off as
residual body
Cytoplasmic bridges break
and sperms release from
Sertoli cells to lie free in
lumen of seminiferous
tubules.
About 74 days are required to
go from a spermatogonium
to a sperm

44. SPERMIOGENESIS (cont.)
A mature sperm has head,
neck and tail
From lumen of seminiferous
tubules sperms enter duct of
epididymis
They take 20 days to travel
this 4-6 meter long tortuous
duct
If ejaculation does not occur
they die and degenerate

45. Abnormal sperms
They are with:
Two heads
Two tails
or:
Dwarf
Giant
Contrary to oocytes
abnormal sperms are
seen more frequently

46. Hormonal Regulation of Testicular Function
The hypothalamus releases
gonadotropin-releasing
hormone (GnRH)
GnRH stimulates the anterior
pituitary to secrete FSH and LH
FSH causes sustentacular cells
to release androgen-binding
protein (ABP)
LH stimulates interstitial cells
to release testosterone
ABP binding of testosterone
enhances spermatogenesis

48. Hormonal Regulation of Testicular Function
Feedback inhibition
on the hypothalamus
and pituitary results
from:
Rising levels of
testosterone
Increased inhibin

49. BLOOD TESTIS BARRIER
Tight junctions between adjacent sertoli cells
near the basal lamina form a blood testis barrier.
It prevents large molecules from passing from
the interstital tissue and part of tubule near
basal lamina to the region near tubular
lumen(adluminar compartment),
and lumen.

51. significance
Blood testis barrier protects different stages of
spermatogenesis from blood borne toxic
substance and from circulating antibodies.
It prevents entry of byproducts of gametogenesis
into the blood that is why autoimmune reaction
does not occur.

52. Androgens
-Includes testosterone, DHT & androstenedione
- Testosterone serves as a prohormone for
Dihydrotestosterone (DHT)
Oestradiol

53. TESTOSTERONE
C19 steriod,secreted by cholesterol in the leydig
cells.
Androstenedione secreted from adrenal cortex.

54. Cholesterol
Pregnenolone
Progesterone
17-α- Hydroxy
pregnenolone
17- Hydroxy
progesterone
Dehydro-epi
androsterone
Andro-
stenedione
Oestrone
Oestriol
TESTOSTERONE OESTRADIOL

55. Regulation of secretion
• Oestrogen – similar to Testosterone
• Inhibin inhibits FSH secretion at A.P level

56. T DHT DHT- R
T- R
R
R
T- R
Nucleus
90%
10%
5-reductase
cytoplasm

57. Testosterone & DHT
• growth of genitals in a boy
• production of sperm
• growth of facial, pubic & axillary hairs
• muscular development
• growth of larynx & voice deepens
• inhibition of bone growth
• thickening of skin, loss of s.c. fat
• behavioral changes in men
• nitrogen retaining effect
• erythropoietin secretion increased
• Increased LDL & decreased HDL

58. Composition of Human Semen.
1.Color: White, opalescent
2. Specific gravity: 1.028
3. pH: 7.35–7.50
4.Sperm count: Average about 100 million/mL, with fewer than 20% abnormal
forms
5.Other components: From seminal vesicles (contributes 60% of total volume)

Fructose (1.5-6.5 mg/mL)
Phosphorylcholine
Ergothioneine
Ascorbic acid
Flavins
Prostaglandins
Spermine
 

59. - From prostate (contributes 20% of total volume)
Citric acid
Cholesterol,
phospholipids
Fibrinolysin,
fibrinogenase
Zinc Acid phosphatase
Phosphate Buffers
Bicarbonate
Hyaluronidase

60. Semen analysis
Motility>60% should be motile with in 3hrs of
collection.
Count >40 million /ml is normal.
Liquify-should liquify with in half an hour.
Morphology->80% should have normal
morphology

61. 

Table 25–5 Distribution of Gonadal Steroids and
Cortisol in Plasma.

    % Bound to Steroid % Free CBG GBG Albumin
Testosterone 2 0 65 33 Androstenedione 7 0 8 85
Estradiol 2 0 38 60 Progesterone 2 18 0 80 Cortisol
4 90 0 6