Reproduction - male anatomy/spermatogenesis Flashcards
What are testes?
Secrete male sex hormones and produce male gametes and sperm
Pass through inguinal ring
What muscles are important for testes thermoregulation?
Dartos and cremaster muscles
what are the structures within the testes and joining to body?
Seminiferous tubules
Rete testes
Efferent ductules
Epididymus ( head/caput, body/corpus, tail/cauda)
Spermatic cord (vas deferens, pampiniform plexus, cremaster muscle)
What are within/between seminiferous tubules?
In the tubules: sertoli cells
Between tubules: Leydig cells
What do sertoli cells do?
Control spermatogenesis by transferring developmental proteins to spermatocytes, they also remove material from elongating spermatids
Joined by gap junctions
What do leydig cells do?
These produce testosterone and stimulate sertoli cells
What is the pathway for testosterone production?
Leydig cell
Cholesterol>Pregnenolone>Testosterone
Sertoli cell
Testosterone?Dihydrotestosterone
What controls testosterone production?
GnRH (hypothalamus)
LH/FSH (anterior pituitary)
LH > leydig cells
FSH > sertoli cells > receptors to be responsive to testosterone
What happens if the pituitary gland is removed?
Testes shrink and no spermatogenesis
Leydig cells deteriorate and little/no testosterone output.
What happens if the testes are removed?
Complete stop of testosterone production and helps control behaviour
What is spermatogenesis?
The production of sperm
How does spermatogenesis occur?
- Spermatogonal stem cells develop and proliferate via mitosis (diploid)
- Spermatocytes undergo meiotic division and become genetically different spermatids
- Spermatids are packaged up and elongated to become spermatozoa via cytodifferentation
Where is spermatozoa concentrated and matured?
In the retis testis and mature in the epididymus
What happens in the caput/head of the epididymus?
The fluid from the sertoli cells is resporbed and the sperm is concentrated
The muscles propel the sperm forward as is not motile or fertile
What happens in the corpus/body of the epididymus ?
The sperm matures and the environment is modified:
- loss of cytoplasmic droplet and nuclear chromatin condenses via disulphide bridges
-surface glycoproteins are added and the lipid composition of the membrane changes to fatty acids
-Metabolic activity is depressed to become dependent on fructose and prolong cell life
-cAMP content of tail increases to aquire motility
What happens in the cauda/tail?
Sperm is stored
What is the pampiniform plexus?
The veins around the testis to ensure cooling before circulating through the scrotum
What are the accessory glands?
Ampulla
Bulbourethral gland
Prostate
What is the composition of seminal plasma?
-Glycoprotein decapacitation factors
-Fructose and sorbitol
-Citric acid (stops coagulation)
-Buffers and ascorbic acid (vaginal pH)
-Acid phosphatase
-Prostaglandins to stimulation muscle contraction
How does an erection/ejaculation occur?
- Pelvic nerve is stimulated, leading to arterial dilation and an increase in blood flow
- Relaxation of retractor penis muscle leads to straightening of sigmoid flexure
- Muscles of vas deferens, seminal vesicles and prostate contract
- Spermatozoa and seminal plasma are expelled
What is the anatomy of a sperm?
Head - acrosome, nucleus
Mid - centriole and mitochondria
Tail - tail
What is a sigmoid flexure?
A flexure so the penis can be kept in the body held by retractor muscles. Fibroelastic penis’s use this.
What animals have as sigmoid flexure?
Bull, ram and boar
What is the corpus cavernosum?
One of two columns of spongy tissue that runs through the shaft (body) of the penis. The corpus cavernosum forms most of the penis and contains blood vessels that fill with blood to help make an erection.
What is the corpus spongiosum?
Another column of spongy tissue that surrounds the urethra
What is a musculovascular penis?
Requires blood flow into the corpus cavernosum to become erect
What species have a musculovascular penis?
Humans, stallions
How do dogs mate?
- Male mounts females, and 1st/2nd fractions of semen are ejaculated (1-2mins)
- Male turns, and a 3rd fraction of semen is ejaculated (5-45mins) with inter-uterine deposition, while maintaining high pressure
- The aminals are locked by the bulbus glandis
What is the anatomy of a bull/ram?
Testes lie vertically in a pendulous manner
Sigmoid flexure/fibroelastic penis
Ram has filiform appendage to spray sperm
What is the anatomy of a boar?
Testes are non-pendulous and are inverted, lying oblique.
Sigmoid flexure/fibroelastic penis
Corkscrew penis
What is the anatomy of a stallion?
Testes lie horizontally, in pendulous manner
Musculovascular penis
What is the anatomy of a tom cat?
Penis points backwards and the testes are located dorsally
Androgen dependent spines on the penis
What is the tunica vaginalis?
A sheet of connective tissue forming the pouch the testis sit in
What is the pampiniform plexus?
The network of capillaries for temperature control of the testes along with the cremaster muscles.
