Male Reproductive System

Question 1

Descent of the Testis

Answer 1

• Testes arise intraabdominally
• starts around 13 weeks
• Develops from meonephric kidney which also develops the excurrent duct system

Gubernaculum

• CT
• As the fetus develops, holds the testis in a lower abdominal position
• in response to hormones, around 7 months, promotes contraction of gubernaculum, it draws the testis down into the scrotum

Question 2

Embryology

Answer 2

• Mesonephric kidney gives rise to part of the testes
• Mesonephric tubules become the efferent ducts
• Mesonephric duct becomes the epididymis
• Mesonephros plays a role in the development of the gonads and retention of the tubules and ducts as part of the excurrent duct system

Question 3

Pampiniform Plexus

Answer 3

Countercurrent heat exchange system

• cools abdominal blood passing to testis and epididymis
• heats blood returning from testis and epididymis to abdomen

Question 4

Testicular Capsule of CT

Answer 4

3 layers

1. Tunica vaginalis
   - single layer of cuboidal epithelium
2. Tunica albuginea
   - Thickest layer
   - CT layer
   - Forms the septa that divides into lobules (seminferous tubules within lobules)
   - mediastinum - thickening of tunica albuginea with cavities into which sperm from semineferous tubules collect and drain into efferent ducts
3. Tunica Vasculosa
   - layer of blood vessels to provide nutrients and oxygen
   - goes between tubules

Question 5

.Leydig Cells

Answer 5

• synthesize testosterone
• found between seminferous tubules
• Abundant smooth ER
• Mitochondria with tubular cristae

Question 6

Seminferous Tubules

Answer 6

Epithelium consisting of:

• Sertoli cells (diploid) - support cells
• Germ cells - various kinds (spermatogonia, primary spermatocytes, etc.)
• at the end of each tubule, there is a terminal segment that is sertoli cells only
• this is connected to the tubulus rectus (simple cuboidal epithelium)
• which is then connected to rete testis

Question 7

LH and FSH Control

Answer 7

• LH stimulates leydig cells to produce testosterone

- FSH causes sertoli cells to produce proteins that support germ cels

Question 8

Testosterone

Answer 8

• maintains spermatogenesis
• Maintains accessory glands
• Secondary sex characteristics (facial hair, muscularity)
• Libido - sex drive

Question 9

Testosterone Synthesis

Answer 9

• starts with cholesterol
• have intermediates
• becomes testosterone
• needs to bind to androgen receptor

Question 10

Sertoli Cells

Answer 10

• Create tight junctions with adjacent sertoli cells
• 3 consequences

1. barrier that prevents blood from getting to the germ cells undergoing meiosis
2. compartmentalize the germinal epithelium
   - Basal compartment - Has interaction with blood vessels
   - Adluminal compartment - no interaction with blood vessels, instead sertoli cells provide nutrients to germ cells (sustaintacular role)
3. Sustentacular role - needed for germ cell viability

Question 11

Spermatogenesis

Answer 11

• going from most primitive spermatogonia to a sperm

spermatogonia undergo various rounds of mitosis

spermatogonia -> primary spermatocytes
- going from 2n to 4n

Primary spermatocytes undergo first meiotic division to produce secondary spermatocytes

Secondary spermatocytes (2n)
- undergo second meiotic division to produce round spermatid

Rounded spermatids - hapoid, 1n
- undergoes elongation to create spermatids

Question 12

Spermiogenesis

Answer 12

• going from a rounded spermatid to an elongated sperm

Question 13

Spermatids

Answer 13

• 1n DNA content = haploid
• acrosomal granule on one end - flattens out on top of the nucleus
• The other end contains centrioles
• from the distal centriole you get the formation of the axoneme (9+2 arrangement of microtubules)
• around the axoneme, mitochondria gather to form the middle piece
• residual body - excess cytoplasm
• phagocytized by the sertoli cells

Question 14

Sperm

Answer 14

Head

• contains DNA
• Acrosome contains hydrolytic enzymes
• needed for going through the follicle for fertilization of the ooctye

Mid Piece

• axoneme (9+2) arrangement of microtubules
• surrounded by outer dense fibers (9 of them)
• surrounded by mitochondrial sheath- provides energy for motility

Principle piece

• axoneme surrounded by outer dense fibers
• mitochondria are replaced by fibrous sheath

End piece
- axoneme only

Question 15

Rete Testis

Answer 15

• Sperm is released from the semineferous tubules into the rete testis
• Rete are spaces in the mediastinum of the tunica albuginea
• lined by simple cuboidal epithelium
• occasional cilia

Question 16

Efferent Ducts

Answer 16

• ductus efferentes
• derived from the meosnephric tubules of the mesonephric kidney
• about 20 ducts bundled together
• lined by ciliated cells and resportion cells
• ciliated cells help to move the sperm along
• Resorptive cells- reabsorb 95% of fluid before entering the epididymis
• becomes very concentrated

Question 17

Epididymis

Answer 17

• one long duct that is highly folded and coiled upon itself
• psuedostratifed columnar epithelium with sterocilia
• reabsorbs fluid, concentrating the sperm
• As sperm goes through the epididymis, from the head to vas deferens, there is an increase in ability to fertilize an oocyte
• The diameter of the duct increases, the flow rate of the sperm declines as it reaches the end of the epididymis

Question 18

Ductus (vas) Deferens

Answer 18

• same tube as epidiymis, therefore derived from the mesonephric duct
• more smooth muscle - used for ejaculatory process
• inner and outer longitudinal
• middle circular

Epithelium becomes more folded

• Folds increase in size as you go down the ductus vas deferens
• lots of folds as you get to the ampulla region

Question 19

Seminal Vesicles

Answer 19

• Pair of seminal vesicles attached to each vas deferens
• Contains one tube that’s highly folded
• simple columnar or pseudostratified columnar epithelium
• secrete fluids during ejaculation that helps to promote the viability of the sperm

Question 20

Prostate Gland

Answer 20

• sits at the base of the bladder
• the two ejaculatory ducts (vas deferens) go thorugh it
• transitional, central and Periurethral zones
• contains more smooth muscle

Lining epithelium is pseudostratified or simple columnar

corpora amylacea
- shows up in the prostate of aging men

Question 21

Bulbourethral Glands

Answer 21

• Cowper’s Glands
• Alveolar Gland
• Secretes mucin
• Base of the penis

Lines the urethra

• protecting from acrosomal proteases
• protects sperm from remains of urine
• skeletal muscle is histologically unique structure

Question 22

Penis

Answer 22

The root
- fixed end of the penis which attaches it to the body wall

The body
- mobile tubular portion

The glans
- expanded distal end surrounding the urethral orifice

Question 23

Histology of Penis

Answer 23

• Paired corpus cavernosum
• Surrounded by CT capsule (tunica albuginea)
• very similar to the clitoris
• urethra surrounded by the corpus spongiosum

Question 24

Male Urethra

Answer 24

Prostatic urethra

• passes through the prostate
• transitional epithelium - some epithelium that lines the prostate

Membranous urethra
- psuedostratified/ stratified columnar epithelium

Penile Urethra
- pseudostratified/ stratified columnar epithelium