Flashcards in Reproduction - male Deck (33)
Name two layers of the testes
1. Tunica vagnalis - sac-like extensions of peritoneum, descends into scrotum with testes (outer layer), flattened mesothelial cells
2. Tunica albunginea - the white fibrous capsule, collagen
3. Tunica Vasculosa - loose connective tissue containing blood vessels and lymphatics
Name the type of spermatid daughter cells in the testis, what do they do?
Type A - remain outside of blood-testes barrier (BTB), they produce daughter cells until they die (dark nuceli)
Type B - these differentiate into primary spermatocytes cells, they then pass through the BTB and move towards the lumen of the testes
Meiosis I then occurs - producing two secondary spermatocytes
Meiosis II then produces 4 spermatids
These spermatids sprout a tail and discard cytoplasm
What occurs in the epididymus?
Site of sperm maturation and storage
Describe the passage of the sperm (SEVEN UP)
S - SEMINIFEROUS TUBULES in the testes (Tubuli recti connect to Rete Testis, then efferent ducts and the epididymis)
E - EPIDIDYMUS
V - VAS DEFERENES (vas and efferent duct join to form ejuact.duct)
E - EJUACTULATORY DUCT
U - URETHRA
P - PENUS
What are the two cell types in the testis?
1. Sertoli cells (produce sperm) - form blood-testes-barrier
-Phagocyotic, protective, supportive
2. Leydig cells (produce testosterone), large amounts of SER (to produce hormone)
contain Reinke's crystals (no known function, useful to identify)
Describe the differentiation of spermatogonia and describe the nucleus at each stage
1. Spermatogenia (type A and B) - uniform nucleus
2. Spermatocyte - speckled nucleus (primary 2n, to secondary n)
3. Spermatid - dense nucleus
4. Spermatozoon - oval nucleus, mature haploid cell
Describe the axoneme of sperm
-Dynein arms act in a similar way to troponin in muscle
-9 +2 arrangement of microtubules (one complete and one partial membrane)
What occurs in the Rete Testis?
(Seminiferous tubules to Tubuli recti to Rete testis to efferent ducts)
-Fluid reabsorption occurs in the rete testis so that the spermatozoa is concentrated
-Cuboidal epi, microvili and cilia
What are stereocilia? Where are they found?
Stereocilia have long projections, immotile (unlike cilia - this means fluid volume propels along)
-Found on epididymis, efferent tubules and van deferenes
What occurs in epididymus?
-Sperm enter the head imotile and leave two weeks later from tail motile :)
-Has head, body and tail
-Reabsorbs seminiferous tubule fluid
-muscle has no peristaltic motion
Describe the vas deferens
-pseudo stratified columnar
-thick 3 layered muscular wall = peristalic motion
-Vas joins the efferent duct to form the ejaculatory duct within the prostate
What is the cremaster muscle?
Covers the testes and the spermatic cord
Describe the prostate and its function
-Secretes alkaline fluid to neutralise acidic environment of female genital tract
-30-50 tubuloalveolar glands with ducts
-Combines with seminal vesicle
-Periurethral mucosal glands
-Periurethral submucosal glands
What do seminal vesicles produce?
Produces 50% volume of fluid for ejaculate
-Empties into ejaculatory duct
What do Cowper's (bulbourethral) glands produce?
Lubricating mucus, empties into post-prostatic urethra
Describe the structure of the penis
-L and R corpora cavernosa on dorsal side
-Corpus spongiosum on ventral side, surrounds urethra
-Rich nerve supply
Name the important features of a sperm
1. head - contains nucleus, cell membrane, acrosome
2. mid piece - mitochondria
3. tail - flagellum, contractile filaments (whip like motion)
What forms the Blood-testes-barrier
-each cell is joined by tight junctions
-prevents the movement of chemicals from blood into the lumen of the seminiferous tubule and helps retain luminal fluid
-different compartments of sertoli cells = different conditions = different germ cell development
What do sertoli cells secrete?
1. Androgen-binding protein (ABP) = this binds to testosterone which crosses sertoli cell barrier to enter tubule
ABP maintains high levels of testosterone also inhibits inhibin (inhibin inhibits FSH secretion) and other paracrine factors
2. Also phagocytose defective sperm
3. secrete müllerian-inhibiting substance in embryonic life
What are some other effects of androgens? (DHT and testosterone) (in boys)
Stimulate bone growth (growth hormone)
Secretion of erythropoietin (increased RBC production)
-increased libido and aggression
What is andropause?
Equivalent of female menopause
-steady decrease of testosterone from about 40 years of age
-decreased sperm motility
-emotional problems = depression is common in older men
Explain hormonal control of male repro
How does it differ from female tract
1. Hypothalamus fires about every 90 mins
2. Secretes GnRH
3. Stimulates anterior pit. to secrete FSH and LH
4. LH acts on leydig cells - they produce testosterone (-ve feedback stoppping ant. pit. from secreting LH) Testosterone acts on other parts of repro tract and other organs
5. FSH stimulates sertoli cells to
a) secrete inhibin (-ve feedback stopping ant. pit. from secreting FSH)
-total amounts of GnRH, FSH, LH and testosterone and fairly constant day to day unlike female tract
* in some cells testosterone is converted to DHT (5-alpha-reductase)
in the brain testosterone is converted to estradiol (aromatase)
How does testosterone affect men?
1. Stimulates spermatogenesis
2. -ve feedback of Lh on ant. pit.
3. -ve feedback decreases GnRH from hypothalamus
4. Induces differentiation of male accessory repro organs and maintains function
5. Secondary male sex characteristics
6. Stimulates anabolism, bone growth and cessation of bone growth
What is in the spermatic cord? Describe the passage to the penis tip
Binds vas deferens, blood vessels and nerves
-passes to the testes through the inguinal canal
-after entering the abdomen the 2 vasa deferentia continue to behind the urinary bladder base
-ducts from the seminal vesicles join the vasa defrentia to form 2 ejaculatory ducts
-the ducts enter the prostate gland (secretes fluid) and join the urethra
-the bulbourethra glands lie below the prostate and drain into the urethra to the penis
What occurs during an erection?
During sexual excitement small arteries dilate, blood flow is increased and 3 vascular compartments become engorged with blood and high pressure - the penis becomes rigid
How is can an erection be stimulated? How does this result in an erection?
1a) descending pathways CNS - triggered by thoughts, emotions, sight and smells *higher brain functions can have a profound stimulatory/inhibitory affect on an erection
1b) input from penis mechanoreceptors
2) neurons to penis
-increase nitric oxide = causes smooth muscles to dilate
-decrease activity of symp neurons (noadrenergic and noncholinergic autonomic neurons are activated. norepinephrinic are inhibited)
3) Penis becomes erect - causes compression of veins - greater erection
What causes ejaculation?
-The discharge of semen is expelled due to;
1. Smooth muscle of epididymus, vas deferens, ejactulatory ducts, prostate and seminal vesicles contract due to symp innervation
2. This empties sperm and glandular secretions into urethra (called emission)
3. Semen is expelled from urethra by a series of rapid contractions of the urethral smooth muscle and skeletal muscle at the base of the penis (during ejaculation the sphincter at the base of the urinary bladder is closed so that sperm cannot enter the bladder and urine cannot be expelled)
What are the two muscles of the penis?
-2 X corpus cavernosum on top (dorsal)
-1 X corpus spongiosum on bottom (ventral)
What is the reduction division? where does it occur?
Primary spermocytes (2n) to secondary (n)
Spermagonia develop to spermocytes, then spermocytes, then reduction divison, then pass through BTB (sertoli cells)
(if passes through BTB then body attacks it like a foreign cell)
(then spermatids, then spermozoa)