Chapter 19 Male Reproductive System 沈 阳 医 学 院 组织胚胎学教研室...

Chapter 19

Male Reproductive System

沈 阳 医 学 院沈 阳 医 学 院 组织胚胎学教研室组织胚胎学教研室

丛敬丛敬

Ⅰ. General description 1. Consists of paired testes, ge

nital ducts, accessory glands and penis.

2. Genital ducts epididymis ductus deferens ejaculatory ducts urethra.3. Accessory glands seminal vesicles prostate bulbourethral glands

Ⅱ. Testes 1. General structure

A. Capsule -- 2 layers:

the visceral layer of tunica vaginalis

tunica albuginea

B. Mediastinum testis

C. Septum + testicular lobules

D. Interstitial tissue

C. Testicular lobules --- highly coiled tubules contained in the lobules.

a. Composition:

Seminiferous tubules

Short straight tubules

Rete testis

Testis section

b. Seminiferous tubules

germinal epithelium:

- a specialized stratified epi

- consists of 2 types of cells: spermatogenic cells (male reproductive cells) Sertoli cells

Lamina propria: basement membrane collagen layer myoid cells.

seminiferous tubules

2. Spermatogenic cells

--include 5 successive cells.

Spermatogonia

Primary spermatocytes

Secondary spermatocytes

Spermatids

Spermatozoa

A. Spermatogonia a. Adjacent to the BM, with round or ovoid nucleus.

b. Classified into type Ad, type Ap, and type B on the basis of nuclear staining.

type A--nucleolus in the periphera of nuclear,

Ad--nuclear dark ; Ap--nuclear pale

type B ---nucleolus in the center of nuclear

c.

Type Ad (stem cells) →Type Ad → type Ad type Ap → type B

Primary spermatocytes

spermatogenesis

B. Primary spermatocytes --- (stop in the prophase of first meiosis for 22 days )

a.The largest cells with nuclei in various stages of meiosis, easily visible, nuclear as woolen ball

b. Contain diploid (2n) chromosomes (44+XY) and tetraploid (4n) DNA. c. Undergo the first meiosis (homologous chromosomes separate) producing the secondary

spermatocytes.

C. Secondary spermatocytesa. Smaller cells near the lumen, with round nucleus, and few i

n number.

b. Contain haploid (1n) chromosomes (22+X or Y) and 2n DNA.

c. Quickly undergo the second

meiosis producing the spermatids.

※not easy to be seen for short-lived

and quickly divide into second

meiosis.

D. Spermatids and spermiogenesisa. The smallest, round or ovoid cells close to the lumen.

b. Haploid cells (1n) in the

number of chromosomes and

in the amount of DNA.

c. Do not divide, and transform

from round cells into tadpole-

like spermatozoa by

spermiogenesis.

d. spermiogenesis:

spermatid spermatozoa

spermatozoon

d. Spermiogenesis includes following changes:

a) The nucleus becomes condensed and elongated.

b) Golgi apparatus transforms into vesicle and then acrosome.

c) Centrioles migrates to a position opposite acrosome and forms the flagellum (axoneme).

d) Mi move and aggregate around proximal part of the flagellum forming a sheath.

e) Much of cytoplasm is no longer required and cast off as residual bodies.

E. Spermatozoona. A mature spermatozoon has a head and a tail, about 60

m in length (head=5um,tail=55um)

tadpole in shape.

E. Spermatozoon

b. The head is pear-shaped, flattened and contains condensed nucleus (22+X or Y). The anterior 2/3 portion of the head is covered by the cap-like acrosome, which contains hydrolytic enzymes in it and is important for fertilization.

E. Spermatozoon

c. The tail is long and slender, containing a 9+2 microtubular axoneme (structure for motility) in its core. It is subdivided into 4 segments:

neck middle Principal terminal piece

E. Spermatozoon

①The neck is very short and contains one centriole.

②The middle has a sheath of mitochondria which provides the energy for motility.

E. Spermatozoon③The principal has a fibrous sheath providing suppo

rt and protection.

④The terminal contains only the axoneme.

E. Spermatozoon

d. The spermatozoa in the testes appear morphologically mature but functionally immature, that is, they are non-motile and do not fertilize the ovum.

Spermatogenesis

The spermatogenesis is the process by which spermatogonia divide and differentiate into spermatozoon

about 64 days from spermatogonium to spermatozoon3 stages

Spermatogenesis

3. Sertoli cell (supporting cell)

pyramidal in shape,

basal--close to the BM

apical--close to the lumen

lateral

--project to lateral processes

--tight junction

3. Sertoli cell (supporting cell)

a. Irregular outline

b. Elongated triangular and pale-stained nucleus with a prominent nucleolus.

c. Abundant SER, as well as RER, Golgi apparatus, etc.

d. Tight junctions between adjacent cells near their bases, which lie in a basal compartment and adluminal compartment

e. functiona) support, protect, nourish, regulate and release germinal cell

b) secret androgen-binding protein (ABP); bind to androgen, maintain the level of androgen concentration of lumen. And inhibin suppresses FSH synthesis and release.

e. functionc) phagocytose degenerated cells and residual bodies from

spermiogenesis.d) constitute the blood-testis barriere) resistant to most factors: radiation, f) high temperature, infection, malnutrition, aging, etc.

blood-testis barrierconstitute:

endothelium and BM of capillary,

CT, and BM of seminiferous epithelium

tight junction between the Sertoli cells.

function:

--- provide micro-environment for spermatogenesis

--- avoid spermatozoon passing through the wall of

seminiferous tubule and from autoimmune reaction

blood-testis barrier

4. Leydig (interstitial) cellsA. Large, round or polygonal cells usually in groups, present i

n the interstitial tissue.

B. Nucleus is large, pale-stained with 1-2 nucleoli.

C. Cytoplasm is acidophilic and has abundant SER, lipid droplets, and Mi with tubular cristae.

D. Secrete testosterone under the control of LH.

hypothalamus hypophysis testis hormone regulate

GnRH FSH

LH

Sertoli cell

interstitial cell (leydig)

ABPInhibinandrogen

spermatogenesis

Control factors during spermatgenesis

5. straight tubules ( tubulus rectus )

position: near the mediastinum testis

shape : straight and short canal

structure: simple cuboidal cells without seminiferous epithelium (thinner wall)

6. rete testisposition: within the mediastinum testis

shape: labyrinthine network (large and irregular lumen)

structure: as straight tubules

Ⅲ. Epididymis

1. Consist of :

--head: the efferent ductules

(8-12 pieces).

--body and tail :

a highly coiled tube, ductus

epididymis (only 1 pieces).

2. Ductus efferents Ductus efferents have an epithelium composed of groups of nonciliated cuboidal cell alternating with ciliated cells.

The nonciliated cells absorb much of the fluid secreted by the seminiferous tubules. The cilia beat towards the epididymis and assist in the transportation of the spermatozoa.

The activity of ciliated cells and fluid absorption create a fluid flow that sweeps spermatozoa toward the epididymis.

3. ductus epididymis The ductus epididymis is lined with a pseudostratified columnar epithelium, containing 2 types of cells. Tall principal cells form a smooth lumen surface andhave numerous stereocilia.Short base cells may be germinative.

Ductus epididymis Ductus efferentes

epididymis duct Efferent duct

4. Has both absorptive and secretory functions

A. Absorbs most of the fluid that leaves the testis.

B. Secretes carnitine, glycerylphosphorylcholine,

sialic acid, etc.

C. Spermatozoa become mature functionally, acquiring motility and fertilizability when they

slowly pass the epididymis.

Ⅳ. Prostate

1. Compound glands around the urethra;

Ⅳ. Prostate

covering: CT and SM

parenchyma: 30-50 compound

tubuloaveolar gland.

-- mucosal gland in the innermost zone(within urethral mucosa)

-- submucosal gland in the middle zone (within submucosal layer)

-- main gland in the peripheral zone (other portions)

2. simple epi ( cuboidal, columnar and pseudostratified )

3. within the cavity, there may be prostatic concretion,

HE: round or oval acidophilic bodies showing

concentric layers

※especially in older man.