Male Anatomy / Histology

Question 1

How are seminiferous tubules arranged?

Answer 1

• Surrounded by fibrous tunica albuginea w/ invaginations that form septa –> 250-400 lobules
• Ea lobule has 2-4 seminiferous tubules –> start and end in common straight seminiferous tubule –> rete testis –> connects to head of epididymis via efferent ductules

Question 2

Role and Location of Sertoli Cells

Answer 2

Location - BM of seminiferous tubules - direct contact w/ germ cells - maintain microenvironment

• FSH –> Sertoli proliferation and seminiferous tubule elongation b/f puberty (more sertoli cells = greater sperm output)
• FSH stimulation of Sertoli cells is not NEEDED for spermatogenesis but supports it
• Sertoli cells themselves are NEEDED for spermatogenesis

Question 3

Blood Testis Barrier

Answer 3

-Created by Sertoli cells w/ tight junctions

• Adluminal side - protected / immune-privileged; undergoing meiosis
  - Immune-privilege can lead to auto-antibody formation on differentiating germ cells –> immune response (orchitis)
• Basal side - exposed to circulation; mitosis
• If endocrine factors cannot cross border then Sertoli cells release paracrine factors that can

Question 4

Role and Location of Leydig Cells

Answer 4

• In interstitial space outside seminiferous tubules

- LH binds Leydig cells (in interstitial space b/n seminiferous tubules); major source of testosterone

Question 5

Progression of Male Gametes

Answer 5

MOVE FROM BASAL TO LUMINAL

• Spermatogonia - mitosis (“keep going thru mitosis - gonia”)
  
  • A dark - non mitotic reserve
  • A pale - stem cells undergoing mitosis
  • B - mitosis but incomplete cytokinesis so clump together
• Primary spermatocyte - 4N; meiosis I (takes 24 days)
• Secondary spermatocyte - 2N; meiosis II (happens very quickly)
• Spermatid - 1N; final product of meiosis; round cell; formation is called spermatogenesis
• Spermatazoa - 1N; matures into sperm shape; elongated w/ head, acrosome and tail (“zoa b/c zoom w/ flagella”); formation is called spermiogenesis

Question 6

Testes on Histo

Answer 6

• Tubules surrounded by basement membrane, lined w/ Sertoli cells and gametes in center
• Sertoli - euchromatic; run all the way from BM to lumen
• Gap junctions b/n them creates mitotic compartment in base (basal) & others
• Myoepithelial cells outside BM can contract to help force sperm out of lumen
• Interstitial space is connective tissue are w/ vessels and Leydig cells
• Can see all stages of sperm maturation above

Question 7

Testosterone Production

Answer 7

• 95% produced in Leydig cells
• Take in cholesterol via LDL and HDL from circulation or from de novo synthesis from acetate or cholesterol esters stored in cellular lipid droplets
• LH stimulation –> cAMP –> testosterone synthesis and release into circulation
• Rate limiting step = transporting hydrophobic cholesterol into inner mito membrane; but acute LH stimulation –> steroidogenic acute regulatory protein which transports the cholesterol

Question 8

DHT

Answer 8

• From testosterone via 5-alpha reductase
• Needed for scotum, penis and urethra development in utero
• Also needed for effects on prostate and sebaceous glands of skin

Question 9

5 Steps of Sperm Transport

Answer 9

• 1- Sertoli cells secrete fluid into seminiferous tubule lumen (including nutrients and sex hormone binding protein w/ testosterone); this fluid then carries sperm to rete testis
• 2- Rete testis –> efferent ductules –> epididymis
• 3- Sperm conc in epididymis by resorption of water and mature here for 15 days until acquire forward motility
• 4- Moved as dense mass to vas deferens by muscle contraction of epididymis and vas deferens (not swimming - too dense)
• 5- Removed w/ urine or w/ seminal fluid if ejaculation

Question 10

Contributions to Seminal Fluid

Answer 10

• Seminal vesicles, prostate, ampulla and Cowper’s gland all contribute to seminal fluid
• Seminal vesicles provide 60% esp fructose and clotting substance
• Prostate provides 30% including PSA (coagulase to free clotted semen) and PAP (prostatic acid phosphatase); alkalize
• Cowper’s glands (pea-sized below prostate) provide lubrication

Question 11

Erection Process

Answer 11

• Inc blood flow in (NO in walls of precapillary arterioles and sinusoids of corpus cavernosum –> inc cGMP–> relaxation and dilation)
• Expanded corpus cavernosum also presses on tunica to dec blood flow out via venous system
• Viagra = PDE5 inhibitor

Question 12

Sperm Structure

Answer 12

• Head - condensed haploid genome
• Acrosomal compartment - on anterior head; filled w/ hydrolytic enzymes
• Midpiece - mitochondria; energy for tail locomotion

Question 13

Capacitation

Answer 13

• In female tract
• Destabilize sperm head membrane to prepare for acrosome reaction; makes it more fluid and permeable to Ca++
• Inc Ca++ in –> inc cAMP –> hyperactive motility

Question 14

Fertilization

Answer 14

• In fallopian tube
• ZP3 glycoprotein of zona pellucida binds sperm –> acrosome reaction (acrosome releases enzymes which drill thru zona pellucida w/ help of driving force of sperm tail) –> fuses w/ plasma membrane of oocyte –> egg cont meiosis and stimulates granule contents of egg into zona pellucida including proteases that alter zona pellucida/destroy ZP3 so no further penetration by additional sperm

Question 15

How is male infertility determined and defined?

Answer 15

• 2 semen samples wks apart after 2-5 days abstinence
• Normal count > 20 mill sperm / ml ejaculate w/ 75% viability, 40% mobility and 30% normal shape and form
• Oligospermic - < 20 mill / ml
• Azoospermia - no sperm in ejaculate; obstructive or non-obstructive

Question 16

Causes of Male Infertility

Answer 16

• 50% idiopathic
• Varicocele
• ID or inflammation (mumps)
• Kallman
• Immune disorders
• Environmental
• Genetics - CF (absence of vas deferens), Noonan Syndrome, myotonic dystrophy, hemachromatosis, XX reversal, male pseudohermaphroditism (androgen insensitivity), XXY Klinefelters, deletions in Y chromosome

Question 17

4 Prostate Zones

Answer 17

• Anterior
• Transitional - around urethra; responsible for BPH
• Central - around seminal vesicles
• Peripheral - 70% prostate cancer

Question 18

Prostate Histology

Answer 18

• Highly folded lumen w/ smooth muscle
• Corpora amylacea - layered concentrations that inc w/ age; including lactoferrin
• Epithelium of basal layer of cuboidal cells and apical layer of columnar cells
• Do cytokeratin stain; if pos then shows normal (epithelium anchored down into BM)

Question 19

Progression of Prostate Neoplasia

Answer 19

• Normal –> proliferative inflammatory atrophy (PIA) –> prostatic intraepithelial neoplasia (PIN) –> localized cancer (adenocarcinoma) –> metastasize

Question 20

Gleason Score

Answer 20

• Score of 1-5 based on abnormality of 12 specimens
• Then add worst + best + most predominant scores
• For prostate cancer

Question 21

3 Roles of Oxytocin in Males

Answer 21

• Up-regulates 5 alpha reductase –> more DHT
• Maintains prostate tone / inc smooth muscle contraction at ejaculation
• Empathy, social learning, mate bonding, parent-child bonding