Lecture 4 and 5: Functional Anatomy of the Male Reproductive Tract Flashcards
Gross Anatomy of the male reproductive tract
scrotum
testes
spermatic cord
excurrent duct system
accessory sex glands
penis and associated muscles for protrusion, erection and ejaculation
prepuce
Gross Function of the male reproductive tract
manufacture and delivery of sperm
synthesis and secretion of androgens
Spermatic Cord
FUNCTIONS:
- suspends testes in scrotum via inguinal canal
- constitute a pathway for blood and lymph vessels, nerves, ductus deferens
- contributes to the regulation of temperature and concentration of testosterone in testes
pulse pressure is reduced considerably when the testicular artery enters the spermatic cord
ANATOMY
testicular artery= coiled network around ventromedial testis
testicular vein: surrounds artery
Pampinoform Plexus
counter current heat exchange (arterial to venous)
- heat from arterial blood is 39º transferred to cooler venous blood at 33º
- maintains testis temperature at 33º (lower than 39º of rest of body)
there is also a counter-current exchange of testosterone but in the opposite direction ( venous to arterial)
[higher testosterone concentration in the testes]
Spermatic Cord: Ductus Deferens
sperm transport (part of excurrent duct system)
Cremaster Muscle:
support of testes and aid of blood flow
continuous with the internal abdominal oblique muscle
striated muscle- intermittent contractions
- pumping action
- enhance venous blood and return to body
- aids on heat exchange and temperature regulation of testes
Scrotum
Functions:
- temperature sensor
- temperature regulation
- protection
- support
Anatomy
two lobed sac with 4 layers
1. skin: low fat and hair, lots of sympathetic thermosensitive neurons
– afferent signal to the brain that responds with efferent nerve impulses to sweat glands in the scrotum and respiratory muscles
– lots of sweat glands
2. tunica dartos- smooth muscle layer capable to maintain sustained contractions changes scrotal location relative to body - cold = contraction - hot = relaxation changes in scrotal surface area - small SA = contraction - more SA = relaxation
- scrotal fascia: provides support
- parietal vaginal tunic: prevents adhesions- free floating testes
Regulation of Temperature in the testes
depends on
- scrotal cooling
- thermosensitive neurons
- sweat glands
- movements by tunica dartos (sustained contraction)
- countercurrent heat exchange in pampiniform plexus
- anatomical arrangement of testicular arteries and veins
- cremaster muscle (intermittent contractions)
important for
- spermatogenesis –> heat stress can compromise process
- Fertilization capacity of the spermatozoa –> reduced if hot
- developmental potential of the zygote –> sperm DNA damaged by heat
Chronic Hyperthermia of testes
potential reasons
- high environmental temperature
- excess fat in scrotum adn spermatic cord
- inflammation by microorganims infections or trauma
- excessive cold and wind-frost damage of scrotum and testicles
Consequences
- reduces spermatogenesis
- damages DNA and alters biology of spermatozoa
- reduces fertilization capacity of spermatozoa
- when fertilization is successful, development capacity of embryo is compromised by damaged DNA and epigenetic factors inherited from the fertilizing spermatozoon
Testes
Function
- primary reproductive organs in the male
- production of:
- spermatozoa
- hormones and proteins. –> especially testosterone
- tubular fluid- transport of spermatozoa from testes
anatomy
- vary in size and shape among species
-common basic structure
1. testicular capsule: covering of testis composed of two layers
visceral vaginal tunic- the outer layer of testis proper
tunica albuginea- connective tissue containing smooth muscle fibres
-septal projections into the parenchyma
- form lobules and join the mediastinum
- contractions- pumping action for movement of spermatozoa
- Parenchyma
functional tissue - 70% of mass
divided into:- tubular compartment (seminiferous tubules)
- semineferous
epithelium
- divided into the basal and adluminal compartment
- germ cells and spermatic cells
- sertoli cells
- somatic nurse cells for sperm, receptors for FSH and testosterone, variety of secretions: androgen binding protein, sulphated glycoproteins, transferrin, inhibin, fluid
- tubular compartment (seminiferous tubules)
tight junctions: attach adjacent Sertoli cells
- separates adluminal from the basal compartment
part of the blood-testis barrier
- prevents immune cells and immunoglobulins from entering the adluminal compartment
peritubular cells (forms the basement membranes)
- surrounds semineferous tubules
- forms basement membrane
- forms blood testis barrier with sertoli cells
- contractions move sperm and fluid to rete tubules
Interstitial compartment
leydig cells
- receptors for LH
- produce testosterone (androgens)
- sex differentiation of fetus
- secondary sex characteristics of adults - development of accessory sex glands blood vessels nerves lymphatics connective tissue
- Mediastinum
central connective tissue core of the testis
house the rete tubules and connects them to the efferent ducts - Rete Tubules
tiny channels through which spermatozoa are transported out of the testis
drain seminiferous tubules- aided by contraction of the testicular capsule and peritubular cells
Excurrent Duct System
function
- final maturation of spermatozoa
- storage of spermatozoa
- delivery of spermatozoa to pelvuc urethra
anatomy
- Efferent Ducts
- converge to a single duct
- convey newly formed spermatozoa and tubular fluid to epididymal duct - Epididymis
- organized into 3 regions
- HEAD tubular fluid absorption , and distal head secreted new fluid
- spermatozoa: no motility, no fertility, proximal cytoplasmic droplet, low disulfide crosslinking (DNA)
-BODY maturation of spermatozoa
additional fluid secretions - biochemical changes
- spermatozoa: some fertility, some motility , bind to oocyte, translocating cytoplasmic droplet, moderate disulfide crosslinking
TAIL proximal tail = storage distal tail = storage and ejaculation sperm - normal fertility, normal motility, binds to oocyte, high degree of disulfide crosslinking , distal droplet: lost
journey takes about 9-14 days total
- Ductus Deferens
convey stored spermatozoa from tail of epididymis to urethra. smooth muscle- contractions transport until ampulla
Accessory Sex Glands
function
- production of seminal plasma
- fluid vehicle for delivery of the sperm in natural breeding
- provides multiple substrates - fructose, proteins
- not strictly required for fertility
Anatomy
- presence and form varies among species
1. vesicular glands: paired glands in dorsal-cranial to the pelvic urethra, absent in dog and cat
- prostate gland: located in close proximity to the junction of the bladder and pelvic urethra, only accessory sex gland of dogs
- Bulbourethral Gland: paired glands near to ischial arch
boar-large glands that secrete gel fraction
Penis
function: copulatory organ and duct for urine
anatomy
- base of penis: attached to the ischaial arch
- Shaft: main portion, spongy areas or erectile tissue , sigmoid flexure in species with fibroelastic penis , point of attachment for retractor penis muscle
- glans penis: specialized distal end -highly populated with sensory nerves
muscles associated with urethra and penis
function - aid with erection, protrusion and retraction of the penis
Anatomy
1. Urethralis: thick striated muscle that surrounds pelvic urethra, movement of sperm to penile urethra
- bulbospongiousus: overlaps the root and extends ventrally, empty the extrapelvic part of the uretrha
- Ischiocavernosis: paired muscle in the root of the penis, connects pelvic urethra with ischial arch
- retractor penis
