Male Reproductive System Flashcards
Function
Production of androgens
Production, nourishment, storage of male gametes
Introduction of male gametes into female reproductive tract
Components
Testes Scrotum Ducts: - epididymal - vas deferens - urethra Glands: - seminal vesicles - prostate - bulbourethral Penis
Testes & scrotum
4cm long, 2.5cm diameter
Enclosed in sac = scrotum
Scrotal septum seperates scrotum in 2 parts
Each testes is suspended from spermatic chord
Passes through inguinal canal to/from abdominal cavity
–> Testes:
Contains.. Vas deferens, testicular artery, cremasteric artery, testicular venous plexus, lymph vessels, nerves
What are the 2 tissue layers covering the testes?
Tunica vaginalis - thin serous outer layer Tunica albuginae - white coat - tough fibrous inner layer (divides testes into testicular lobules)
Testicular lobules
Each testes is divided into 300 by each tunica albuginea
Each lobule contains 1-4 seminiferous tubules
Site of spermatogenesis
What are seminiferous tubules?
Walls formed of sertoli cells
Sertoli cells secrete nutrients for developing spermatozoa
Spermatogenic cells are in the walls(most immature by basement membrane)
At maturity, sperm released into the lumen
What is mitosis?
Division of parent cell into 2 daughter cells that are genetically identical
Diploid (2n)
What is meiosis?
Division of parent cells into 4 daughter cells with half the number of chromosomes
Haploid (n)
Forms gametes
Spermatogenesis
- Diploid spermatogenia duplicte –> diploid primary spermatocytes
- Primary spermatocytes divide into 2 haploid daughter cells –> secondary spermatocytes
- Secondary spermatocytes divide into 4 haploid daughter cells = spermatids
- Development of spermatids into mature spermatozoa
Structure of sperm
Head —- acrosome (outer) nucleus (inner)
Neck
Middle piece —- spiral mitochondria, axoneme
Tail (flagellum)
What are the 2 cells in seminiferous tubules called?
Sertoli cells - required for maturation of spermatozoa - form 10% of cells in testes - necessary for spermatogenesis - support and nourishment - more developing sperm towards lumen - produce fluid for transport - forms blood-testes barrier - prevents immune response - secrete testicular fluid: > inhibin > androgen-binding protein > Mullerian-inhibiting substance Leydig cells - secrete androgenic steroids near capillaries
How does the endocrine system control the male reproductive system?
- release of GnRH from anterior pituitary gland
- Stimulates release of FSH and LH
- FSH travels to the seminiferous tubules and sustentacular cells, which cause the secretion of inhibin, synthesis of androgen-binding protein and stimulation of spermatogenesis
- LH travels to the interstitial cells, causing the secretion of testosterone, causing the stimulation of sustentacular cells to release inhibin, ABP and spermatogenesis
- the release of testosterone also has affects on the CNS, causes stimulation of bone and muscle growth, establishes and maintains male secondary sex characteristics, and maintenance of accessory glands and organs
What happens if sperm count is too high?
Inhibin release is increased, negative feedback on FSH and GnRH by hypothalamus
What happens if sperm count is decreased below 20 million?
Inhibin release is decreased
Temperature control of testes
Testes kept just below body temperature at 35c
Testes are drawn closer to the body by the cremaster muscle in response to cold
Dartos muscle decreases SA and assists cremaster
Testes cooled by heat exchange at pampiniform plexus
Describe the duct system
Straight seminiferous tubules Rete testis Efferent ductules Epididymal duct Vas deferens Ejaculatory duct Urethra
Epididymis
Attached to posterior surface of testes
Spermatozoa are matured and stored in the tail
Continuous with bas deferens
Vas deferens
45cm long fibromuscular tube-
narrow lumen surrounded by thick smooth muscle layer
Ascends posterior to testis along spermatic chord
Enters abdominal cavity through inguinal canal
Dilated terminal portion (ampulla) joins the ejaculatory duct
Stores and conveys spermatozoa (expelled by peristalsis)
VASECTOMY = sperm still produced but deteriorates and are phagocytosed, success of reversal depends on patient eg age
What are the accessory glands and what do they do
Seminal vesicles
Prostate gland
Bulbourethral gland
These glands produce the majority of semen (sperm + accessory gland secretions)
Seminal vesicles
Convoluted muscular glands 5-7cm long
Posterior to bladder
Joins vas deferens to form ejaculatory duct when sperm and seminal fluid mix
Yellowish viscous alkaline fluid containing fructose, ascorbic acid, prostaglandins, coagulating enzymes
- 60% semen volume
Prostate gland
Lies inferior to bladder Surrounds prostatic urethra Milky, slightly acid fluid containing citrate and enzymes, and prostate-specific antigen Role in activating sperm - 30% semen volume Has tubular-alveolar glands Main prostatic glands in outermost ring
Problems with prostate gland
Often enlarged in older males: benign prostatic hyperplasia
- lower urinary tract symptoms:
- increased frequency, nocturia, weak stream
Treatment:
- alpha adrenergic blockers eg. tamsulosin - reduce smooth muscle tone
- 5-alpha reductase inhibitors eg. finasteride - blocks conversion of testosterone to dihydrotesterone
Prostatitis:
- acute or chronic
- pain when urinating and ejaculating, general discomfort in pelvic area
Treatment:
- acute = antibiotics and painkillers
- chronic = antibiotics, analgesics
Prostate cancer
To do with levels of prostate-specific antigen
- during coughing and sneezing prostatic blood may enter vertebral veins
- lower vertebral and pelvic metastases
Bulbourethral glands
Pea-sized glands inferior to the prostate gland
Lined by mucus-secreting epithelium
Mucus-like secretion enters urethra during sexual arousal
Drains into spongy part of urethra
Neutralised urine residue
