Male reproductive system

TestisMonkey, H & E× 3

• TA: TUNICA ALBUG-

INEA, very dense CT

capsule.

• INCOMPLETE CT

SEPTA radiate from

mediastinum into

parenchyma to

form 250 lobules

per testis.

Testicular tunicae:Most external: visceral tunica vaginalis propria covered by mesothelium

Functional Histology 2004

• Each LOBULUS contains 1-4 seminiferous tubules (ST), lined by GERMINAL

EPITHELIUM. The lenght of one tubule is 30-70 cm!

• This epithelium produces immature spermatozoa.

• The seminiferous epithelium is encircled by a basement membrane and a

WALL formed by collagenous fibers, fibroblasts, and contractile myoid cells.

Myoid cells are responsible for the rhythmic contractile activity that propels

the nonmotile sperm to the rete testis.

Sperm acquire forward motility after they have passed through the

epididymal duct.

• Between the coils of ST lie blood and lymph capillaries, CT fibers,

fibroblasts, mast cells, and testosterone-secreting Leydig interstitial cells.

Lobuli testis

Seminiferous Tubule (ST) is highly coiled, ca 70 cm!

ST is supported by the 1. basal lamina, plus 2 or more alternating 2. layers of

collagen fibres, and 3. muscle-like/myoid cells (M).

Functional

Histology

2004

SPERMATOGENESIS in the germinal epithelium is

initiated by the pituitary hormone FSH and passes

through the stages:

(a) spermatogonium, spheroid cell lying basally

divides mitotically for several generations, then

becomes a

(b) primary spermatocyte, larger, divides by the first

meiotic division (to halve the chromosome number to

haploid 23 and introduce genetic variety), to produce

(c) secondary spermatocytes, small, soon

undergoing the 2nd meiotic division, maintaining

the chromosome number at 23 to give

(d) spermatids, smaller and incompletely

separated, which, without dividing transform by

the process of spermiogenesis - into

(e) spermatozoa, released into the tubule's

lumen.

Spermiogenesis: ovoid spermatids transform into slim, movable spermatozoa, it takes ca. 3 weeks

JUNQUEIRA 2004

Major stages of spermiogenesis

Stevens, Lowe, Histology,

Major stages of spermiogenesis

The development of the flagellum proceeds from a distal centriole:

typical axoneme is surrounded by outer dense fibres and a fibrous sheath;

The proximal part of flagellum called middle pieceis encircled by mitochondria.

Development of the acrosome:

synthesis and storage of hydrolytic enzymes in acrosomal sac is required for fertilization.

Stevens, Lowe, Histology

Functional

Histology

2004

THE SPERMATOZOON is a very elongated motile cell, with a cell membrane

enclosing the:

• acrosomal head cap with an enzyme - proacrosin - to aid binding to and

penetration of the zona pellucida of the oocyte

• nucleus, streamlined in shape, with dense chromatin,

• neck joining the HEAD (nucleus and head cap) to the

• flagellar TAIL

Functional

Histology

2004

TAIL,of a spermatozoon is composed of:

a) middle piece, with an axial axonemal core of microtubules in a cilium-like

array, 9 dense longitudinal fibers (F) and a sheath of mitochondria (Mi)

ending at the annulus (An)

b) principal piece, with both longitudinal and circumferential (Rb) fibres

around the axoneme;

c) end piece, with microtubules like a cilium, however, there are

no dense fibres.

Blood-testis barrier

• Adjacent Sertoli cells are united by band-like, (tight)

occluding junctions.

• These junctions divide the seminiferous tubule into a basal

compartment and an adluminal compartment.

Spermatogenesis is protected to a degree by the tight

attachments between the capillary endothelial cells and,

separately, between the Sertoli cells, creating a two-tiered

blood-testis barrier, for example, against immune attack

(protection of developing sperm cells from autoimmune

reactions).

The inner protected compartment of the seminiferous tubule is

the 'adluminal' compartment.

JUNQUE I RA

2004

Functions of the Sertoli cell

• Structural and metabolic support of differentiating spermatogenic cells.

• They protect, nourish, and release the spermatids.

• Maintain blood-testis barrier

• phagocytose excess cytoplasm (residual bodies) released by maturing

spermatids

• secrete fluid into the lumen that transports spermatozoa through the excretory ducts

• secrete androgen-binding protein (ABP) under the influence of folliclestimulating hormone (FSH) from the anterior pituitary. ABP binds and concentrates testosterone.

• secrete inhibin that inhibits synthesis and release of FSH

Interstitial Leydig cells

• stimulated by the LH hormone of the anterior pituitary they secrete testosterone

• large eosinophilic cells located between seminiferous tubules

• Ultrastracture typical for steroid-secreting cells:

abundant SER, tubular-type mitochondria, smooth

ER, lipid droplets

• Characteristic feature are crystals of Reinecke

Seminiferous tubules continue via straight tubuli recti into cuboidal epithelium-lined ducts of rete testis, which lead through the mediastinum to roughly 6-12 ductuli efferentes.

They take spermatozoa to a

single, coiled, tubular

EPIDIDYMIS located behind

the testis.

DUCTUS DEFERENS is a thick-

walled duct. Peristaltic

contractions of its smooth

muscles moove sperm along

the duct.

JUNQUEIRA 2004

Tests, epididymis, and vas deferens

Paths traversed by spermatozoa

1. Efferent ducts/Ductuli efferentes/Head of epididymis

Unevenly lined by simple, columnar, epithelial cells, in groups of tall ciliated

and short secretory cells: the wall has circular smooth muscle;

functions - reabsorption of the fluid used to move sperm out of the testis;

MATURATION OF THE SPERM.

2. Epididymis/ductus epididymis (body and tail)

Regularly lined by tall, absorptive, columnar principal cells with non-motile

stereocilia, and smaller basal cells, together forming a pseudostratified

columnar epithelium:

outside the basal lamina is a little smooth muscle and, between the coils,

is a stroma of dense connective tissue with capillaries;

FUNCTIONS - AS FOR DUCTULI EFFERENTES.

Maturation of spermatozoa takes place in the epididymis

• Head of epidydimis– Not motile - swim in

circular motion

– Not fertile

• Body of epidydimis – some spermatozoa show

motility

– Some are fertile and may bind to oocyte

• Tail of epidydimis – Normal motility

– Fertile

– Able to bind to oocyte

• Transport of sperm through the epidydimis takes 9-13 days depending on species – and is mandatory

DUCTUS DEFERENS

• Lined by epithelium similar to that of the epididymis, that is

supported by a lamina propria: in the ampulla, this mucosa has

many folds.

• most of the very thick wall is SMOOTH MUSCLE: inner,

longitudinal; middle, circular; outer, longitudinal

• adventitia made of CT binds it to nerves, blood and lymphatic

vessels, and skeletal cremaster muscle, to comprise the

SPERMATIC CORD

FUNCTION - RAPID TRANSPORT OF SPERM DURING EJACULATION,

UNDER CONTROL OF SYMPATHETIC NS.

EJACULATORY DUCTS arise on both sides from the dilation of the ampulla of ductus deferens• Lined by pseudostratified or simple columnar epith that rests on CT, no smooth muscle• Ducts open into the prostatic urethra through a hillock on the posterior urethral wall -verumontanum = colliculus seminalis with its blind recess –utriculus masculinus.

Accessory glands of the male reproductive tract. Three sets of glands connect

to the ductus deferens or urethra: the paired seminal vesicles, the prostate, and the paired bulbourethral glands. Prostate - solid tissue mass which secretes during copulation, secretion contains mainlyionic compounds (NaCl, Na citrate), and a variety of enzymes. Bulbourethral (Cowper's) – small, muscular gland associated with caudal pelvic urethra, contain large volume of stored gel (sialic acid) which is emitted during ejaculation.

Basic Histology, 12 ed.

PROSTATE GLAND: 30-40 tubulo-alveolar glands

Lobulated by septa of CT with much smooth muscle.• Divided, with histology and rectal-probe ultrasound, into several zones:

o peripheral(prone to cancer)o transitionalo centralo periurethral (subject to benign prostatic hyper-trophy

JUNQUEIRA 2004

A diagram of a transverse section of the penis shows the relationships of the three erectile

bodies, tunica albuginea, and major blood vessels.

The corpus spongiosum (CS) is on the ventral side of the penis and surrounds the urethra (U). Two corpora cavernosa (CC) fill the dorsal side and all three bodies of cavernous or erectile tissue are surrounded by dense, fibrous tunica albuginea (TA). Along the dorsal side run the major blood vessels (V) and deep in each mass of erectile tissue are smaller blood vessels (V), including the central arteries. Externally the penis is covered by skin (S) attached to the tunica albuginea or neighboring connective tissue. X15. H&E.

Structure of the penis

ENDOCRINE TESTIS

LEYDIG interstitial CELLS constitute a diffuse, steroid-secreting

endocrine gland; lie outside the tubules' basal lamina. They are

controlled by gonadotrophic Luteinizing Hormone (LH) of the

anterior pituitary, and produce the androgenic hormone.

TESTOSTERONE is responsible for:

(a) spermatogenesis

(b) development and maintenance of reproductive ducts

and accessory glands

(c) secondary sexual characteristics:

- male mating behaviour

- anabolic effects on metabolism.