Lecture 18: Reproduction (Male Anatomy Spermatogenesis)

Question 1

What are some of the male reproductive organs? What is the overall major function of the male system?

Answer 1

-Major function is to produce and deliver spermatozoa to the female

Major organs:
-Testis that has spermatogenesis
-Epididymis is covering one half of the testes which is where the sperm matures
-Cremaster muscle propels sperm down spermatic cord and duct down from the epididymis to the probate gland passing the liver
-Prostate gland is sperm get mixed in with other fluids to form semen
-Bulbourethral gland
-Retractor muscle
-Glans penis (penis head)

Question 2

What is the process of sperm from the testes to ejaculation?

Answer 2

1. Testes
   -Makes lots of spermatozoa/day
   -Must be at the correct temperature
2. Final maturation
   -‘Finishing shops’
   - Putting finishing touches
3. Sperm is ready and waiting
   -storage for 5-10 ejaculations
   -Smooth muscle contacts upon sexual stimulation

4.Mixed with fluid from accessory gland
-Metabolic substrates
-Surface coatings

5.Delivery system
-Erection
-Protrusion
-Emission
-Ejaculation

Question 3

Why is temperature control key?

Answer 3

-Testes need to be kept 4-6 C below temperature for spermatogenesis (need a cooling system)
-During late part of gestation or early life: testicular descent via the inguinal canal (towards the scrotum) is required if not ill never produce sperm
-Later in life: temperature by thee veins of the “pampiniform plexus” (in the spermatic cord) forming a countercurrent heat exchange

Question 4

What happens outside the testes?

Answer 4

-Testes are located in the scrotum= skin sac from the abdominal cavity with a layer of smooth muscle (tunica dartos) (projection of skin from abdominal cavity)
-On the inside of the scrotum: layers of connective tissue (scrotal fascia and partial vaginal tunic)
-Covering the testes is a layer of vascularized connect tissue (tunica albuginae + visceral vaginal tunic) that projects septa in the testis
-Smooth muscle cover the septa (helping moving immature sperms)

Question 5

What are the 2 major parts inside the testes?

Answer 5

1. Seminiferous tubules (S.T): site of sperm production. Ducts collect sperm to rate testis in the centre= tubes that bring the sperm to the epididymis
2. Interstitial (b/w S.T) composed if connective tissue, nerve, blood vessels, and Leydig cells which produce testosterone

Question 6

What is some general information about the boar reproductive tract?

Answer 6

-Testis structured similar to bull but more pronounced interstitium (leydig cells produce wider array of androgens, C16, C19 steroids plus estrogens)
-Testis location against the abdominal cavity reduces efficiency of heat exchange (closer to the body and adapt to environmental changes)
-Large seminal vesicles = large volume (produce bulk semen)
-Large bulbo-uretheal glands = gel (produces gel last part of ejaculation to prevent leak
-Copious ejaculate/prolonged ejaculation
-Smaller sperm ‘reserves’ vs bull (collect bull more than boar but seminate more bc larger ejaculate

Question 7

Briefly explain the process of spermatogenesis.

Answer 7

Set of mitotic divisions close to the basal lamina

3 components
-Proliferation: A phase in the basal lamina, still spermatogonia
-Meiosis: move closer to the Sertoli cells, reduction of genetic material, maturation as enter meiosis 1= 64 to 128
-Differentiation: maturation, meiosis 2 256 spermatids, right # of chromosomes but nt sperm nothing to swim etc. Pack genetic material in head of sperm, grow tail

Question 8

What is the process of meiosis?

Answer 8

Interphase: replication of DNA (4chromatids - 2n)
Prophase 1:
-Leptotene: condensation of chromatin
-Zygotene: pairing of homologues (forming a tetrade) ie 2 chrom physically interacting with each other
-Pachytene: crossing-over and recombination
-Diplotene: Synaptonemal complexes dissociate
-Diakinesis: Chiasma disappear and homologues begin to repel

Metaphase 1: homologue centimetre binds to spindle fiber

Anaphase 1: homologous pairs separate and begin to move

Telophase 1: Chromosomes migrate to each pole, cell division. 1 chromosome of pair in each cell = (2c-1n)

Prophase 2: Spindle fibres rearrange and chromosomes recondense

Metaphase 2: Chromosomes align along spindle equator

Anaphase 2: Sister chromatids separate and move to opposite poles

Telophase2: Daughter cell nucleus has one set of chromosomes (1c-1n)

Question 9

What are Sertoli cells?

Answer 9

-Blood testis barrier
-Basal/luminal and adluminal compartments
-Provide nutrients and several factors to control spermatogenesis
-‘fluid pumping’ during final maturation of sperm
-Produce androgen-binding protein (modulates testosterone) and inhibin (inhibits FSH by pituitary) which is produced by sertoli
-Express FSH receptors (regulated by FHS)

Question 10

What is spermiogenesis?

Answer 10

-In contact with Sertoli cells
-Nuclear condensation
-Formation of the acrosomal cap (derived from Golgi) (enzymes packed in vesicles and put into cap, physically enter oocyte to fertilize)
-Development of tail (to propel)
-The distal centriole provides a template for accretion of cytoskeletal elements comprising the contractile lattice of the tail
-Mitochondria become concentrated into the sheath of the middle piece

Question 11

What are leading cells?

Answer 11

-Interstitial cells- located in the spaces b/w tubules
-Highly perfused (blood vessels/capillaries)
-Synthesize androgens -testostone (main fxn of leydig cells)
-Express LH receptors

Question 12

What happens from the head of the epididymis to the tail?

Answer 12

-Head: immotile, infertile
-Body: acquisition of potential to be- motile, fertile
-Tail: Upon dilution- motile, fertile

-Waits in the distal tail before going through the ductus deferent

Question 13

What are some of the accessory glands and why are they important?

Answer 13

Ampler gland (ampullae, absent in boar and dogs) = enlargement of the ductus defferent

Vesicular (asset in dogs) secretes
-Fructose: sperm energy pack
-Vitamins and prostaglandins important for mobility and survival
-Proteins for coagulation

Prostate: alkaline substances to enhance motility

Bulbourethral: alkaline substances to neutralize acidity and mucus to lubricate vagina during copulation

Question 14

What are the steps for arousal?

Answer 14

1. Sensory stimulation: optic, olfactory, tactile and auditory (depends on species)
   2.Stimulation of nerves in the supraoptic and paraventricular nuclei (just know hypothalamus)
2. Release of oxytocin from posterior pituitary
3. Contractions of smooth muscle in distal tail of epididymis and ductus deferens
4. Transport of spermatozoa into an ejaculatory position

Question 15

What are the steps of the Ejaculatory process?

Answer 15

1. Intromission (penetration)
2. Sensory stimulation of glands penis (temperature and pressure)
3. Sudden and powerful contraction of urethralis, bulbospongiosus and ischiocavernosus muscles
4. Expulsion of semen (into female repro. tract)

Question 16

Can we stimulate the ejaculatory phase without a dummy or female?

Answer 16

yes
-Innervation of the male genital system
-Level of the sacral vertebrae
-A way to artificially stimulate w/o prior arousal
-Called “electro ejaculation”
-Various collection tools, with heater to keep harm, or pressure