1. Histology of Male Reproductive System

2. Lecture Objectives
Describe the histological features of the male reproductive system

3. Male Reproductive System
The male structures of reproduction include the:
testes,
a system of ducts
ductus epididymis
ductus deferens
ejaculatory duct
urethra
accessory sex glands
seminal vesicles
prostate gland
bulbourethral glands
supporting structures
penis

4. Testis: General Organization
Tunica vaginalis – extension of peritoneum
Tunica albuginea – dense CT layer
Mediastinum – projection of the tunica albuginea
Lobules – formed from septa from the tunica albuginea

6. Seminiferous Tubules General structure – 200-500 m in length
Tunica propria – lamina propria surrounding the seminiferous tubules
Myoid cells – 3-5 layers thick, synthesize collagen, contractions help move sperm through the tubules
Basal lamina
Seminiferous epithelium – complex stratified epithelium composed of spermatogenic cells and sertoli cells

7. Spermatogenic cells
Type A spermatogonia – ovoid nuclei, can be either type A dark (stem cells) or type A pale (committed to become sperm)
Type B spermatogonia – formed by mitotic division of type A pale cells, connected to each other by cytoplasmic bridges
Primary spermatocytes – result from the mitotic division of type B spermatogonia, large nuclei with dark staining condensed chromatin
Secondary spermatocytes – formed from the first meiotic division of primary spermatocytes
Spermatids – formed following the second meiotic division
Spermatozoa – formed following spermiogenesis

8. Sertoli (Supporting) Cells
Structure
Long cytoplasmic processes extending between spermatogenic cells
Contain inclusion bodies of Charcot-Böttcher
Functions
Blood-testis barrier – formed from unique tight junctions, separates sperm from immune system
Hormones – release inhibin, androgen binding proteins
Respond to FSH and testosterone
Support – support and nourish spermatocytes, therefore, also known as supporting or sustentacular cells
Other characteristics – do not replicate

9. Leydig Cells Structure Location – interstitium of seminiferous tubules
large, polygonal, acidophilic
Contain lipid droplets & Reinke crystals
Location – interstitium of seminiferous tubules
Function – secrete testosterone in response to LH
Do not replicate
Produce testosterone during early fetal life but are inactive until puberty

10. Spermatogenesis
Note: during spermatogenesis, the developing sperm are connected to each other by cytoplasmic bridges. This ensures synchronous development of each clone
Spermatogonial phase (mitosis)
Type A darkm→itosisType A palemi→tosisType A palem→itosisType B m→itosis primary spermatocytes
Spermatocyte phase (meiosis)
Meiosis I – primary spermatocyte forms two secondary spermatocytes (separation of chromosomes)
Meiosis II – secondary spermatocyte forms two spermatids containing haploid DNA (separation of chromatids)

12. Spermiogenesis there are four phases: Golgi phase Cap phase
Proacrosomal granules – contain glycoproteins (enzymes); granules fuse to form the acrosomal vesicle
Acrosomal vesicle – located near the nuclear membrane; its location determines the anterior pole of the developing sperm
Axonal complex – migration of centrioles to the posterior pole to initiate synthesis of axonemal complex of sperm tail
Cap phase
Acrosomal cap – acrosomal vesicle condenses and covers the anterior half of nucleus
Acrosome phase
Reorientation of spermatid with head pointed down into Sertoli cell
Lengthening of flagellum
Manchette – organization of cytoplasmic microtubules
Centrioles migrate back to nucleus to initiate formation of the neck region
Maturation phase
Residual body – excess cytoplasm is pinched off and phagocytized by Sertoli cells

13. Structure of a Mature Sperm
Head – nucleus & acrosomal cap
Neck – centriole, excess nuclear envelop, striated columns
Tail
Middle piece – 9 outer doublets, central doublet of MTs, 9 outer dense fibers, mitochonderial sheath
Principle piece – outer dense fibers gradually decrease in number and are surrounded by a fibrous sheath
Tail end piece – microtubules, no dense fibers

15. Intratesticular Ducts
Straight Tubules (Tubuli recti)
Location – immediately after seminiferous tubule
Epithelial lining – Sertoli cells only at junction with seminiferous tubules becoming simple cuboidal near rete testis
Function – transport of sperm
Rete Testis
Location – interconnecting within CT of mediastinum
Epithelial lining – simple cuboidal to low columnar
Function – transport
Efferent Ductules
Location – rete testis connects to 20 efferent ductules
Epithelial lining – pseudostratified columnar (sawtooth appearance due to presence of tall ciliated columnar cells used for moving sperm and low columnar cells with microvilli used for fluid absorption; basal cells are also present)
Muscle layer – first appearance of a layer of smooth muscle; elastic fibers are interspersed among the muscle cells

16. Ductus epididymus
Efferent ductules coalesce to form a single ductus epididymis Structure – highly coiled; 4-6 m long
Divisions – head, body, tail
Tail is the principle reservoir of mature sperm
Epithelium – pseudostratified columnar with stereocilia
Muscular layer – gradually thickens
the tail has three layers: inner and outer longitudinal and middle circular layer.
The muscle of the head and body move sperm by peristaltic contraction; sperm is ejected during ejaculation by muscle of the tail
Function
Sperm reservoir (tail region)
Fluid absorption and phagocytosis of remaining residual bodies and damaged sperm
Secretion
Further development of sperm – addition of surface glycosides to inhibit sperm binding to egg
Ejection of sperm during ejaculation

17. Vas deferens Ejaculatory ducts Structure
Epithelium – pseudostratified columnar with microvilli
Three muscle layers – inner & outer longitudinal, middle circular
Ampulla – enlargement of the distal end where it is joined by the duct of the seminal vesicle
Functions – secretory; transport
Ejaculatory ducts
Structure – continuation of the vas deferens through the prostate gland
Epithelium - pseudostratified columnar with microvilli
Other features –
NO muscle layers except fibromuscular tissue of the prostate
Empties into the prostatic urethra
Functions – secretory; transport

18. vas deferens
Epididymis

19. Seminal Vesicles Structure
One primary lumen; numerous primary and secondary folds that increase surface area
Pseudostratified columnar epithelium
Inner circular and outer longitudinal muscle layers which contracts during emission adding stored secretions to seminal fluid
Function
produces and secretes 60% of the volume of semen
secretion is viscous, whitish-yellow containing fructose, simple sugars, ascorbic acid, amino acids and prostaglandins.
Secretion requires testosterone

20. Prostate Gland Structure – Consists of 30-50 tubuloalveolar glands
lined with pseudostratified or simple columnar epithelium.
The glandular components are arranged in three layers:
Mucosal layer (central zone) – empty directly in the urethra
Submucosal layer (transition zone) – glands empty first into the prostatic sinus and then into the urethra
Peripheral layer (peripheral zone) – the main prostatic glands, empty into prostatic sinuses
Prostatic concretions (corpora amylacea) – precipitated secretory material that may be calcified, found in alveoli particularly in older men
Capsule – fibroelastic CT and smooth muscle, contracts during emission
Function – produces 30% of semen volume.
Secretion is milky fluid containing citric acid, cholesterol, acid phosphatase, fibrinolysin, and electrolytes
Benign prostatic hypertrophy (BPH) & cancer
BPH normally occurs in older men in the mucosal and submucosal glands
malignancies occur in the epithelium of the main peripheral glands

22. Glands of Littre (urethral glands)
Bulbourethral Glands
Structure – tubuloalveolar, mucus secretory glands lined with simple columnar epithelium
– Surrounded by intermixed smooth & skeletal muscle
Function – secretes preseminal fluid that lubricates the penile urethra prior to ejaculation
Glands of Littre (urethral glands)
Structure – predominantly around penile urethra
Function – mucus secretion protects epithelium from urine

23. Penis
Structure
Erectile tissue – three cavernous bodies surrounded by loose elastic connective tissue with an outer covering of thin skin
skin extends over the glans penis (prepuce or foreskin) unless removed by circumcision.
A thick fibrous sheath called the tunica alboginea surrounds each cavernous body.
The cavernous bodies consist of irregular vascular spaces separated by trabeculae of dense fibroelastic tissue.
The 3 bodies are:
Corpora cavernosa – two dorsal erectile tissues of the penis
Corpus spongiosum (corpus cavernosum urethrae) – ventral erectile tissue, surrounds urethra

24. Results from adrenergic (sympathetic) stimulation
Erection
Results from parasympathetic postganglionic efferent impulses which cause penile arteries to dilate, more blood enters cavernous spaces, cavernous body distends compressing veins, engorgement results in erection
arterial dilation also mediated by nitric oxide produced by endothelial cells
Note: Viagra enhances the effects of nitric oxide resulting in vasodilation
Emission
Results from adrenergic (sympathetic) stimulation
stimulation causes movement of sperm from the tail of the epididymis and contractions of the vas deferens, seminal vesicle and prostate gland
Ejaculation
Results from contraction of skeletal muscle surrounding the corpora cavernosa (the ischiocavernosis) and the corpus spongiosum (the bulbospongiosus)
muscle contraction ejects semen out of the urethra