Male Reproductive System

what are the general functions of the reproductive system

- gametogensis

- fertilization

- development and nourishment of a new individual

- production of reproductive hormones

what are the parts of the male reproductive system

- testes

- ducts (epididymis, ductus deferens, urethra)

- supporting structures (scrotum and penis)

- accessory glands (seminal vesicles, prostate gland, bulbourethral glands)

what are the major reproductive hormones of the male reproductive system

- GnRH, secrete LH and FSH

- LH or ICSH, synthesis and secretion of testosterone

- FSH, support spermatogensis

- testosterone, secondary sex characteristics

what is the scrotum

a sac-like structure that contains the testes and is divided into 2 internal compartments by an incomplete CT septum

what are the compartments of the scrotum externally marked by

raphe = a midline irregular ridge that extends posterior to the anus and anterior into inferior surface of penis

what are the 2 muscles of the scrotum that help regulate temp of the testes

- cremaster, contract and pull testes near body when cold and vice versa

- dartos, wrinkles skin and reduced overall size and vice versa

what is the perinum

diamond- shaped area between thighs that is bounded by the symphysis pubis, coccyx, and ischial tuberosities

what is the perineum divided into

anterior urogenital triangle (base of penis and scrotum) and posterior anal triangle (anal opening)

what are testes

small oval shaped organs within the scrotum that function as both endocrine and exocrine glands

what is the major exocrine secretion vs major endocrine secretion of the testes

sperm cells - testosterone

what is the importance of the testes

site of spermatogenesis, specifically in the seminiferous tubules

why are the testes an external structure of the body

sperm requires lower-than body temp

what is the tunica albuginea

the thick outer part of the testes consisting of mostly fibrous CT that then forms the septa to divid the testes into lobules that contain seminiferous tubules to develop sperm

what does the loose CT that surround the seminiferous tubules contain

clusters of endocrine cells called interstitial cells/Leydig cells that secrete testosterone

where do the seminfierous tubules empty

tubuli recti which turn into rete testis

what is the pathway of sperms to the epididymis

seminiferous tubules -> tubuli recti -> rete testis -> efferent ductules -> epididymis

what do the efferent ductules pass through

tunica albuginea to exit the testis

where do the testes originally sit and then how do they descend

pass from abdominal cavity through inguinal canal to the scrotum

what are inguinal rings

openings in aponeuroses of transverse abdominis, internal, and external oblique that is known to be a weak area of the abdominal wall and can herniate

what is cryptorchidism

Failure of testes to descend into scrotum → prevents normal sperm development due to higher temperature

what is the gubernaculum

Fibromuscular cord that guides testes into scrotum

steps of testes descent

1. At ~8 weeks after fertilization, testes are nonmesenteric, retroperitoneal organs near the developing kidneys

2. The gubernaculum connects testes to the labioscrotal swelling and guides descent

3. The gubernaculum shortens, pulling testes toward the inguinal canal

4. Between 7-9 months, testes pass through the inguinal canal (weak abdominal wall area)

5. The process vaginalis (peritoneal outpocketing) precedes the testes

6. Testes reach the scrotum before birth, where cooler temperature supports sperm development

7. The superior process vaginalis degenerates after descent

8. The inferior portion remains as the tunica vaginalis, a serous membrane that reduces friction

what does the labioscrotal swelling become

the scrotum

what is the tunica vaginalis

serous membrane consisting of a layer of simple squamous resting on a basement membrane that surrounds most of the testis

what does the tunica vaginalis secrete and why

a small amount of fluid to allow the testes to move without friction in the scrotum

where is the site of spermatiogenesis

seminiferous tubules

what are the 2 types of cells in the seminiferous tubules

germ cells and sustentacular cells

mitosis in spermatogensis

Spermatogonia divide → primary spermatocytes + daughter spermatogonia

meiosis I in spermatogenesis

primary spermatocytes → 2 secondary spermatocytes

meiosis II in spermatogensis

each secondary spermatocytes divide → 2 even smaller cells = spermatids

what does each spermatid contain

one of each of the homologous pairs of chromosomes (each sperm has 22 autosomes and either an X or Y)

what do spermatids develop

an acrosome and flagellum

what is an acrosome

A capsule of enzymes on the anterior portion of the sperm cell head that has the enzymes needed for the sperm to penetrate the oocyte

what does each spermatid undergo in the last phase of spermatogenesis

spermiogenesis to form a mature sperm cell by developing a head, mid piece, and flagellum

what are sertoli/sustentacular cells

nourish sperm cells and produce a number of hormones (androgens, estrogens, and inhibins) and form blood-testis barrier

Blood-Testis Barrier

Protects developing sperm from immune system

Leydig (Interstitial) Cells

Produce testosterone in response to LH

Testosterone Conversion

sustentacular cells convert testosterone → dihydrotestosterone (DHT) and estradiol

what do interstitial cells secrete

testosterone

what does the head of sperm contain

DNA and acrosome covering (contains enzymes to penetrate egg)

what does the midpiece of the sperm contain

mitochondria

what occurs in spermiogenesis

Spermatids develop into sperm with head, midpiece, and tail/flagellum

what is the pathway of sperm

Seminiferous tubules → tubuli recti → rete testis → efferent ductules → epididymis

what is the function of the epididymis

site of sperm maturation and storage

how long does it take for the sperm to travel through the epididymis and appear in the ejaculate

12-16 days

what does the sperm consist of once in the epididymis

has a head, body, and long tail

ductus/vas deferns

Transports sperm from epididymis to abdominal cavity

what are the contents of the spermatic cord

Ductus deferens, testicular artery, venous plexus, lymphatics, nerves, process vaginalis remnants

what is the spermatic cord

a bundle of nerves, ducts, and blood vessels connecting the testicles to the abdominal cavity

what covers the spermatic cord

External spermatic fascia, cremaster muscle, and internal spermatic fascia

what is the ampulla

widened distal end of ductus deferens near the prostate gland

what does the wall of the ductus deferens have

smooth muscle that exhibits peristalsis during ejaculation

what is the seminal vesicle

A gland that secretes fluids that help compose semen and joins the ampulla of ductus deferens to form the ejaculatory duct

location of ejaculatory duct

end at urethra within prostate gland

what is the importance on inhibin that is secreted by the sertoli cells

provides negative feedback to the pituitary to specifically inhibit FSH

what is the urethra

tube that carries urine and male reproductive fluids from the bladder to distal end of penis

what are the 3 parts of the urethra

prostatic, membranous, spongy/penile

prostatic urethra

connected to the bladder and passes through the prostate and 15-30 prostatics ducts empty into the urethra

membranous urethra

Extends through perineum (muscular floor of pelvis -> urogenital diaphragm)

spongy/penile urethra

passes through the penis and several mucus-secreting urethral glands empty here

functions of the penis

Urination, erection, delivery of sperm

what are the 3 columns of erectile tissue that engorge with blood in the penis

corpora cavernosa, corpus spongiosum, crura and blub

corpora cavernosa

two columns of erectile tissue found in the shaft of the penis and expands at the base for form the crus which attaches the penis to the pelvic bones

corpus spongiosum

one column of erectile tissue that surrounds the spongy urethra and expands to form the bulb

crura and bulb

together they make up the root of the penis

glans penis

bulging structure of corpus spongiosum at the distal end of the penis

prepuce

covers glans penis (circumsision = surgical removal)

what is the external urethral orifice of the penis

Opening for urine and semen

seminal vesicles

sac-like glands next to ampulla of ductus deferens and joins with it to form the ejaculatory duct (60%)

what do the secretions of the seminal vesicle contain

fibrinogen and nutrients

what is the pH like in the seminal vesicles

high

prostate gland

has both glandular and muscluar tissue that secretes thin, milky alkaline fluid with clotting factors & fibrinolysin (30%)

bulbourethral glands (Cowper's glands)

small glands near membranous urethra that secrete mucus before ejaculation and help neutralize vaginal pH (5%)

semen vs. sperm

- Semen = fluid mixture

- sperm = male gametes

what is semen

secretions of all 3 accessory glands + sperm

what do the testes secrete into the semen

a small amount of fluid for motility of sperm

what does the urethral mucosa do

add mucus to semen

what is the normal sperm count

75-400 million/mL

what is the normal ejaculation amount

2-5 mL

puberty

age at which individuals become capable of sexual reproduction = about 12-14

what occurs prior to puberty

GnRH secretion (from hypothalamus) is inhibited by adrnal testosterone

what occurs at puberty

the pituitary is less sensitive to the GnRH inhibition which ↑GnRH = ↑LH & FSH = testosterone

LH function in males

Stimulates Leydig cells → testosterone

FSH function in males

Stimulates Sertoli cells → spermatogenesis

how does the urinary and reproductive system work together for electrolyte management

While the kidneys manage K+ and Na+ via Aldosterone , the reproductive system also utilizes Inhibin and sex steroids that can influence overall fluid balance

how does the urinary and digestive system have homeostatic compensation

The kidneys compensate for metabolic disturbances by reabsorbing Bicarbonate and excreting H+ ions -> this is critical if digestive processes (like severe vomiting or diarrhea) alter the body's pH

how does the urinary system and the liver regulate pressure

The liver synthesizes the plasma protein Albumin, which is essential for maintaining the colloid osmotic pressure that opposes filtration in the kidney -> if the liver fails, filtration dynamics in the nephron are significantly altered