Male Anatomy / Histology Flashcards
1
Q
How are seminiferous tubules arranged?
A
- 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
2
Q
Role and Location of Sertoli Cells
A
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
3
Q
Blood Testis Barrier
A
-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
4
Q
Role and Location of Leydig Cells
A
- In interstitial space outside seminiferous tubules
- LH binds Leydig cells (in interstitial space b/n seminiferous tubules); major source of testosterone
5
Q
Progression of Male Gametes
A
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
6
Q
Testes on Histo
A
- 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
7
Q
Testosterone Production
A
- 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
8
Q
DHT
A
- 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
9
Q
5 Steps of Sperm Transport
A
- 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
10
Q
Contributions to Seminal Fluid
A
- 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
11
Q
Erection Process
A
- 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
12
Q
Sperm Structure
A
- Head - condensed haploid genome
- Acrosomal compartment - on anterior head; filled w/ hydrolytic enzymes
- Midpiece - mitochondria; energy for tail locomotion
13
Q
Capacitation
A
- 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
14
Q
Fertilization
A
- 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
15
Q
How is male infertility determined and defined?
A
- 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
