The Male Reproductive System YONG-MEI CHEN ( 陈咏梅 ) Dept. of Anatomy, Histology & Embryology Peking Union Medical College Tel:69156461 E-mail address: pumc_he@126.com
Content Spermatogenesis Spermiogenesis Structure & function of Sertoli cell & Leydig cell Structure & function of Genital ducts, accessory glands & penis
I. Introduction:
I. Introduction:
II. Testis Migration of primordial germ cells (PGCs)
descent of testis Cryptorchidism
Structure of testis 1. Testicular capsule: (1) tunica vaginalis: (2) tunica albuginea lobuli testis mediastinum testis (3) tunica vasculosa
2. Seminiferous tubule total length is nearly 0.5 km (1) tunica propria muscle-like myoid cells (2) basal lamina (3) seminiferous (or germinal) epithelium stratified epithelium
1) Spermatogenic cells Spermatogenesis & meiosis a. Spermatogonia: located in basal compartment, mitosis Dark type A spermatogonia: heterochromatin Pale type A spermatogonia: euchromatin Type B spermatogonia: only b. Primary spermatocyte: the largest male germ cells, having chromosome within cells. c. Secondary spermatocytes: short-lived cells d. Spermatid
Spermiogenesis: round spermatids elongated spermatids through shedding of much of their cytoplasm, rearrangement of their organelles, and formation of flagella
Main changes during spermiogenesis: Golgi apparatus acrosome Centriole flagellum Mitochondria mitochondrial sheath Microtubule manchette (caudal tube) Nucleus becomes condensed and elongated sperm head Residual bodies are shed, and phagocytosed by Sertoli cell
acrosome (acrosomal cap): a specialized lysosome, proacrosomal granules acrosomal granule within a acrosome vesicle
e. Spermatozoon morphologically mature Head Neck Tail: middle piece, principal piece, end piece
Clonal nature of the germ cells Syncytium of germ cells Cytoplasmic bridges
2) Sertoli cells a. Structure: LM: tall columnar cell; a large, pale, oval or irregular shaped nucleus; a prominent nucleolus; invisible lateral cellular limits.
EM: cell membrane & nucleus with infoldings; many organelles; tight junctions & gap junctions.
Blood-testis barrier Basal compartment Adluminal compartment
b. Functions: Support, protection and nutrition of developing germ cells. Secretion. e.g.: androgen-binding protein (ABP), inhibin & antimüillerian hormone, and a fructose-rich medium. Formation of blood-testis barrier. Regulation the release of`spermatozoa. Phagocytosis of residual bodies.
3. Interstitial tissue (1) Interstitial cell (Leydig cell): 1) Structure: LM: always in clusters; large, polyhedral cell; acidophilic cytoplasm; central located nucleus.
EM: containing numerous of SER, mitochondria with tubular cristae, and lipid droplets. 2) Function: secretion of testosterone.
(ICSH)
(2) Others: including C.T., Nerve, Blood & Lymphatic vessels.
4. intratesticular genital ducts:
(1) tubuli recti (straight tubules): Lined by Sertoli cells in proximal half and simple cuboidal epithelium in distal half, supported by loose C.T.
(2) Rete testis: A system of labyrinthine spaces housed within the mediastinum testis, lined by simple low cuboidal epithelium, supported by vascular C.T.
(3) Ductuli efferentes: Forming the head of the epididymis, lined by pseudostratified columnar E.
III. extratesticular genital ducts
1. Ductus epididymidis Forming the body and tail of the epididymis. Lined by pseudostratified columnar E., basal cells: principal cells: long stereocilia.
2. Ductus deferens (Vas deferens) pseudostratified columnar E.
Spermatic cord: passes through the inguinal canal, including arteries, veins and ductus deferens.
Pampiniform plexus Countercurrent heat-exchange system
3. Ejaculatory duct 4. Urethra (1) Prostatic urethra Transitional E. (2) Membranous urethra pseudostratified columnar E. (3) Spongious part pseudostratified columnar E. Glands of Littre
IV. Accessory sex glands
1. Seminal vesicles Highly coiled tubuli, simple cuboidal-columnar to pseudostratified columnar E., producing fructoserich seminal fluid
2. Prostate gland (1) Mucosal glands (central zone) (2) Submucosal glands (transition zone) (3) Main glands (peripheral zone)
Branched tubuloalveolar glands, Simple cuboidal-columnar to pseudostratified columnar E.
Prostatic concretions (corpora amylacea)
3. Bulbourethral glands Tubuloalveolar, mucus-secreting glands, lined by a simple cuboidal or columnar epithelium.
V. Penis
1. Structure: Each of three columns of erectile tissue, which is encircled by tunica albuginea, has large venous sinuses separated by trabeculae. (1) Corpora cavernosa of the penis: Paired, located dorsally. Helicine arteries (2) Corpus cavernosum of the urethra (corpus spongiosum): ventrally located, containing penile urethra.
Helicine arterie Intimal cushion
2. Functions: (1) Urination (2) Copulation organ Penile erection: a hemodynamic event
Spermatogenesis Summary
Spermiogenesis
Sertoli cell
Interstitial cell (Leydig cell):