ERS21 Histology Of Male Reproductive System

Question 1

Components of male reproductive system

Answer 1

1. Gonads
   - Testes: spermatogenic stem cells that continuously divide
   —> produce new generations of spermatozoa/sperm/male gametes
   —> produce sex hormones
2. Reproductive tracts
   - Epididymis: storage and maturation of sperm
   - Ejaculation: sperm leave Epididymis via Ductus/Vas deferens —> exit through Urethra
3. Accessory glands
   - Prostate
   - Seminal vesicle (paired)
   - Bulbourethral glands (paired)
   —> variety of secretion added to sperm to form semen
4. External genitalia
   - Penis: copulatory organ
   - Scrotum: support testes

Question 2

Structure and Functions of Testes

Answer 2

1. Tunica albuginea
   - thick connective tissue capsule surround testes
2. Septum
   - extension of Tunica albuginea
3. Mediastinum testes
   - thickened part of Tunica albuginea
   - hilum of gland

ALL continuous

• ***Dense irregular CT
• Structural support + Protection for tubular system of testes

4. Tunica vaginalis
   - external of Tunica albuginea
5. Lobule
   - ~250 incomplete compartments
6. Seminiferous tubule
   - 1-4 coiled tubes in each lobule lined by ***Germinal epithelium (Stratified)
   - spermatogenic cells divide, mature, transformed into sperm
7. Straight tubule
   - continuation of Seminiferous tubule
   - enter Mediastinum testes to form network of tubes: Rete testis
8. Rete testis
   - newly released sperm pass to Straight tubules —> enter Rete testis
9. Efferent ductules
   - short tubules leading to Epididymis

Sequence: Seminiferous tubule —> Straight tubule —> Rete testis —> Efferent ductules —> Epididymis —> Vas deferens —> Ejaculatory duct —> Urethra

Question 3

Structure and Functions of Reproductive tract

Answer 3

1. Epididymis
   - storage and maturation of sperm
2. Vas deferens
   - strong contraction of smooth muscle expel sperm towards ejaculatory duct and urethra during sexual excitation
3. Ejaculatory duct
   - continuation of Vas deferens
4. Urethra
   - Prostatic urethra: **Transitional
   - Membranous urethra: **Pseudostratified columnar
   - Spongy/Penile urethra: ***Non-keratinized Stratified squamous

Question 4

Structure and Functions of Accessory glands

Answer 4

Secretions of accessory glands (Non-cellular) + Spermatozoa
—> Semen
—> Ejaculates from penis into cervix, increase likelihood of sperm penetrating cervical mucus and enter central lumen of uterus

1. Seminal vesicle (paired)
   - key role in normal functioning of semen
   - 70% of semen volume
   - **Semenogelin, **Fructose, Ascorbic acid, Stimulators of sperm motility
2. Prostate (15-30%)
   - secrete **Proteolytic enzymes (Prostatic acid phosphatase) into semen
   —> **break down Semenogelin in ejaculate
   —> allow semen remain in fluid state
   —> moving throughout female reproductive tract for potential fertilisation
   - Citric acid, Zinc
3. Bulbourethral glands (paired)
   - secrete ***Alkaline lubricating mucus secretion —> contribute to final volume of semen (5%)

Question 5

Structure and Functions of External genitalia

Answer 5

1. Penis
   - 3 masses of erectile tissue
   —> Corpus cavernosum (paired)
   —> Corpus spongiosum
   - engorged with blood —> penis erect during sexual stimulation
2. Scrotum
   - fibromuscular cutaneous sac

Question 6

***Epithelial lining of reproductive system

Answer 6

1. Seminiferous tubules —> Germinal epithelium (production of sperm cells)
2. Straight tubule —> Simple cuboidal
3. Rete testis —> Simple cuboidal
4. Efferent ductules —> Columnar with cilia
5. Epididymis —> Pseudostratified columnar with stereocilia (help movement of sperm during ejaculation)
6. Vas deferens —> Pseudostratified columnar with stereocilia
7. Ejaculatory duct —> Pseudostratified columnar with stereocilia
8. Seminal vesicles —> Glandular (production of supportive substances in semen)
9. Prostate —> Glandular
10. Bulbourethral glands —> Glandular
11. Urethra
    - Prostatic —> Transitional
    - Membranous —> Pseudostratified columnar
    - Spongy/Penile —> Non-keratinized Stratified squamous (reproductive + urinary function)

Question 7

Gonads histology

Answer 7

Testis:

1. Tunica albuginea
2. (Interlobular) Septum
3. Mediastinum testes
   - location of Retes testis

ALL dense irregular CT: Structural support + Protection for tubular system of testes

4. Lobules (300) (divided by septum)

• Parenchyma (functional role)
  —> Seminiferous tubules (1-4 blinded ended) —> Straight tubules —> Retes testis (in Mediastinum testes)

- Stroma (supportive/protective role, in-between tubular organs)
—> Blood vessels
—> Lymphatic vessels
—> Nerves
—> Interstitium (Leydig cells)

Question 8

Seminiferous tubules histology

Answer 8

Features:
- Germinal epithelium (thick)
—> Sertoli cells + Spermatogenic cells
- Thin layer of CT
- Highly convoluted —> form loops

Parenchyma (Seminiferous tubules / Germinal epithelium):

1. Sertoli cells
   - support Spermatogenic cells
   - surrounded by thick Basal lamina
2. Spermatogenic cells
   - i.e. Spermatogonia —> Spermatozoa

Stroma (outside of Seminiferous tubules):

3. Myoid cells / Myofibroblasts (epithelial-like, smooth muscle cells)
   - surround Seminiferous tubules
4. Leydig cells (Interstitial cells)
   - produce Testosterone
   - ***Reinke crystals
   - abundant reddish cytoplasm
5. Other cells: Endothelial cells, Smooth muscle, Neurons

Question 9

Spermatogenesis

Answer 9

• Spermatozoa/Sperm formation process
• Begins at puberty, when Leydig cells start to produce Androgens
• Non-motile Spermatogonia —> Spermatids
• occur on each side of wall of Sertoli cells independently —> ***no synchronous production of sperm
• 65-75 days, simultaneously at different times, regions —> ***even production and availability of sperm
• Development of **Acrosomal cap, **Flagellum

**Spermatogonia (diploid 2N 2C (46) immature sperm cells from embryonic germ cells) dividing by mitosis
—> DNA replication —> **Primary spermatocytes (2N 4C (46x2))
—> Meiosis 1 —> **Secondary spermatocytes x2 (1N 2C (23x2))
—> Meiosis 2 —> **Spermatids (haploid 1N) x4 (1N 1C (23))
—> Spermiogenesis —> ***Spermatozoa/Sperm cells (1N 1C (23)) (Spermiogenesis: Spermatids mature into Sperm)

Question 10

Spermatozoa

Answer 10

1. Head
   - Acrosome
   - Nucleus
2. Neck
   - Connecting piece
3. Tail
   - Midpiece
   —> Mitochondrial sheath
   - Principal piece
   - End piece

Released into lumen of Seminiferous tubules
—> transported into Epididymis, inside Testicular fluid produced by Sertoli cells
—> ***Non-motile at this stage

Question 11

Sertoli cells (Sustentacular cells)

Answer 11

• Elongated, ***Pyramidal in shape
• Nucleus: Triangular shape, Prominent nucleolus
• Partially envelope spermatogenic cells
• Basal side: Basal lamina
• Apical side: Lumen of Seminiferous tubules
• Lateral side: Processes surrounding spermatogenic cells

1. ***Support, protect and nourish spermatogenic cells
   - mediate exchange of nutrients and metabolites
   - protect spermatogenic cell lines from autoimmune attacks
2. Secrete supporting substances
3. Phagocytose cytoplasmic remnants of Spermatids
4. Establish **Blood-testes barrier
   - **Tight occluding junctions near Basal lamina (binding adjacent Sertoli cells together)

• Mechanical barrier that separate blood from Seminiferous tubules
  —> very few substances from blood found in Testicular fluid
• Protect spermatogenic cells
  —> from immune system, bloodborne noxious agents once Primary spermatocyte undergo meiosis (∵ becomes genetically different)
  —> Primary spermatocytes move towards lumen and new tight junction forms behind it
• Basal compartment: Interstitial fluid + Spermatogonia
• Luminal compartment: Testicular fluid + Lumen of Seminiferous tubules + Intercellular spaces down to level of tight junctions

Question 12

Interstitium

Answer 12

Space between

• Basal lamina of adjacent Seminiferous tubules
• Basal lamina of capillaries

Occupied by CT:
- Collagenous fibres hold tissue together

Cells:
1. Leydig cells
- becomes apparent during puberty
- dispersed through interstitial tissue between Seminiferous tubules
- exist as small clusters
- large round nucleus in centre
- **Testosterone synthesis
—> abundant, tightly packed **sER (typical feature of steroid-secreting cells)
—> well-developed **Golgi apparatus + **Mitochondria
—> released via Fenestrated capillary
- ***Reinke crystals (unknown function) in cytoplasm

2. Myoid cells
   —> have characteristics of smooth muscle
   —> ***peristaltic waves of contraction to pass along Seminiferous tubules
   —> propels spermatozoa towards Straight tubules
3. Fibroblast
4. Mast cells, Macrophages

Question 13

Reproductive tracts

Answer 13

Intratesticular ducts:

1. Straight tubules
   - short tubules continuous with Seminiferous tubules
   - gradual loss of spermatogenic cells
   - Sertoli cells (initially) —> ***Simple Cuboidal cells (later)
2. Rete testis
   - within Mediastinum testes
   - highly anastomotic network of channels
   - **Simple Cuboidal cells with **numerous short microvilli with single flagellum
3. Efferent tubules
   - 10-20 short tubules
   - pierce Tunica albuginea to conduct sperm to Epididymis
   - gradually fuse to form Epididymis
   - **Smooth muscle cells outside basal lamina —> also helps in propelling content
   - **Non-ciliated Cuboidal cells —> **resorb most luminal fluid by Sertoli cells
   - **Ciliated Columnar cells —> to move sperm

Question 14

Epididymis

Answer 14

• Single highly coiled tube
• **Pseudostratified columnar epithelium with stereocilia (help movement of sperm during ejaculation)
  —> **uptake + digestion of the residual bodies eliminated during spermatogenesis

Cells:

1. ***Basal cells (round)
2. ***Principal cells (columnar) with Stereocilia (Basal cell上面)
3. Smooth muscle (最外層包住)
   - peristaltic contraction propel sperm

Question 15

Vas deferens, Ejaculatory duct

Answer 15

Vas deferens
- Straight tube —> muscular
- Continues towards Ejaculatory duct —> Prostate
- Narrow lumen
- Folded mucosa
—> Pseudostratified columnar epithelium with stereocilia
—> lie on thin Lamina propria rich in elastic fibres

Cells:

1. Basal cells
2. Columnar cells with Stereocilia
3. Smooth muscle (thick, **3層)
   - **Inner longitudinal
   - **Intermediate circular
   - **Outer longitudinal
   - strong peristaltic contraction —> expulsion of sperm during ejaculation

Ejaculatory duct

• Continuation of Vas deferens —> enter Prostate
• Pseudostratified columnar epithelium with stereocilia
• ***Muscle layer disappears

Question 16

Male Urethra

Answer 16

• 15-20 cm long
• Carries:
  1. Urine from urinary bladder to penile opening
  2. Semen during ejaculation

Epithelium

• Prostatic: Transitional
• Membranous: Pseudostratified columnar
• Spongy/Penile: Non-keratinized Stratified squamous

Question 17

Seminal vesicles

Answer 17

• NOT reservoir for spermatozoa
• paired
• highly coiled ***tube, irregular lumen
• posterior to bladder, superior to prostate gland
• ***excretory duct joins dilated / terminal part of Vas deferens —> form Ejaculatory duct

Mucosa:
- **Glandular epithelium supported by extensive lamina propria
—> rich in secretory granules
- Seminal fluid (stored in lumen)
1. Alkaline —> neutralise acid in female reproductive tract
2. **Fructose —> energy source for sperms
3. **Semenogelin (coagulation)
4. **Sperm motility
5. ***Stability of sperm chromatin
6. Suspension of immune activity in female reproductive tract

Muscularis

• Inner circular
• Outer longitudinal

Adventitia

• surround Muscularis
• blend with CT

Question 18

Prostate

Answer 18

• surrounded by dense CT capsule
• inferior to neck of bladder
• 30-50 ***branched tubules empties into urethra by small ducts

Features:
1. **Glandular acini
- size variable
- wide irregular lumen of ducts
- thin, watery, slightly **acidic fluid (accumulate in lumen)
—> **Citrate —> energy source for sperm motility
—> Amylase
—> **Prostatic acid phosphatase —> cleave Semenogelin
—> **Prostate Specific Antigen (PSA) —> used in diagnosis of prostatic cancer (concentration ↑ in blood during malignancy)
- concentric layers of condensed prostatic secretions
—> **Prostatic concretions (characteristic feature)

2. ***Glandular epithelium
   - Simple Columnar
3. ***Fibromuscular stroma (characteristic feature)

Histological division:

1. Central zone
2. Fibromuscular zone
3. ***Transitional zone (where BPH arise)
4. Peripheral zone
5. Periurethral gland region

Question 19

Benign Prostatic Hypertrophy

Answer 19

• 30% men >50 yo
• frequency and severity ↑ with age
• caused by hyperplasia of **Glandular + **Stromal cells
  —> non-malignant enlargement of gland

Question 20

Bulbourethral glands (Cowper’s glands)

Answer 20

• small, pea size
• embedded into skeletal muscle of ***Urogenital diaphragm
• excretory duct terminate in ***proximal Penile urethra
• virtually devoid of pathological changes in human

***Tubular alveoli glands:
- Each lobule composed of acini
—> Open into central located canal
—> fibrous CT surround and separate acini

• Clear, slippery, mucous fluid during sexual arousal
  —> **Lubricant for penile urethra + **Alkalinity neutralise acidity present in urethra due to residual drops of urine
  —> contribute to final volume of semen

Question 21

External genitalia: Penis

Answer 21

1. Excretory organ of urine
2. Copulatory organ for deposition of sperm into female reproductive tract

Erectile tissue

• Dorsal: Corpus cavernosum (paired)
• Ventral: Corpus spongiosum (expand distally) —> surrounding Urethra

Features:

1. Tunica albuginea
   - strong CT layer cover erectile tissue
2. Erectile tissue: Irregular vascular spaces
   - lined by endothelium
   - **trabeculae between spaces contain collagen + elastic fibres + smooth muscle
   - blood enters via **Dorsal artery (Cavernosum上面) + ***Deep artery of penis (Cavernosum入面)
   - drained by peripheral veins
3. Urethra (Spongiosum入面)
   - extend through entire length of Corpus spongiosum
4. **Layers
   - Skin
   - Superficial fascia (Colles’ fascia) —> Superficial dorsal veins
   - Deep fascia (Buck’s fascia) —> **Deep dorsal vein, Dorsal artery, Dorsal nerve
   - Tunica albuginea

Question 22

Scrotum

Answer 22

Skin pouch divided by Scrotal septum into 2 sacs

1. Skin
   - loose, thin, corrugated, pigmented
   - epidermis: Keratinised squamous epithelium
   - dermis: divided in half by midline Cutaneous raphe/groove (Perineal raphe) —> continues to inferior penile surface + along perineum to anus
2. ***Dartos muscle and fascia (袋縮)
   - 2 coherent plexuses / bundles of smooth muscle cells
   - contracts in cold / during sexual stimulation
   —> regulate temperature of testes (normal sperm production 2-3oC below body temp)
3. **External spermatic fascia
   - **continuation of Aponeurosis of External oblique muscle
4. **Cremasteric muscle
   - small bundles of skeletal muscle
   - **continuation of Internal oblique muscle
5. **Internal spermatic fascia
   - partitioned in midline
   - **continuation of Transversalis fascia
   - attached to Tunica vaginalis
6. Tunica vaginalis (parietal + visceral layer)