Spermatogenesis, oogenesis & fertilisation Flashcards
What are the testes
Male reproductive glands, suspended in the scrotum
Size- 4.5 cm x 2.5cm x 3cm
3 layers
What is the tunica vaginalis in the testes
Outer covering of membrane formed from peritoneum
What is the tunica albuginea of the testes
Fibrous covering, forms septa which divides testes into lobes
What is tunica vasculosa of the testes
Network of capillaries
What are the internal structures of the testis
Seminiferous tubules, leydig cells, epididymis and vascular deferens
What are the seminiferous tubules of testis
Convoluted loops of germinal epithelium, produce spermatozoa
What is leydig cells of the testis
Lie between seminiferous tubules, produce testosterone after puberty
What is epididymis of the testis
Single highly convoluted tubule forming a mass at upper pole of testis - 6cm long
What is a vas deferens of the testis
Duct formed from epididymis as it leaves the scrotum
What is spermatic cord of the testis
Suspend testes in scrotum contains vas deferens, blood, lymph vessels and nerves
What is the blood supply to testis
Testicular arteries and veins
What is the nerve supply to testis
Branch of 10th/11th thoracic nerve- ilioinguinal nerve
What are seminal vesicles
2 fibromuscular pouches, 5cm long
Lie at posterior base of the bladder
Join vas deferens by small duct to form ejaculatory duct which then joins urethra
Secrete seminal fluid ( alkaline)
Neutralises acidic environment of female reproductive tract of intercourse
Provide energy for sperm and assists coagulation of semen after intercourse
What is the prostate
Doughnut shaped gland - 4cm x 3cm x 2cm
Inferior to bladder and surrounds urethra
What is the function of the prostate
Produces milky coloured prostatic fluid composing 30% of volume of semen
Slightly acidic nature helps semen coagulate after intercourse then breaks down this clot
What are the bulbourethral glands associated with the prostate
Pea sized glands inferior to prostate alkaline fluid to protect sperm and secrete mucus to lubricate penis prior to intercourse
What is the penis
External male sex organ
Passage for ejaculation of semen and excretion of urine
Root and body- root in perineum- body surrounds urethra
Composed of 3 columns of erectile tissue
What is the corpora cavernosa
2 lateral columns
What is the corpus spongiosum
Midventral column containing urethra
What is a glans penis
Expanded triangular distal end covered with retractable foreskin- prepuce
What two ligaments support penis
Fundiform and supensory ligaments
What is the blood supply to penis
Branches of internal pudendal arteries and veins
What is the nerve supply to penis
Autonomic and somatic nerves
What is erection of sexual inercourse
Caused by parasympathetic stimulus resulting in massive increase of blood to fill the corpus cavernosa and corpus spongiosum
What is ejaculation in sexual intercourse
Sympathetic reflex, bladder sphincter closes, peristaltic action of vas deferens, seminal vesicle, ejaculatory ducts and prostate propel semen into the penile urethra
Has two phases
What happens in 1st phase in ejaculation
The vas deferens contract to squeeze the sperm toward the base of the penis and the prostate gland and seminal vesicles release secretions to make semen
What happens in. 2nd phase of ejaculation
Muscles at the base of the penis contract every 0.8 seconds and force the semen out of the penis in up to 5 spurts
What is male puberty
Average onset age - 12/13 yrs
Influenced mainly by body mass
Triggered by gonadotrophin releasing hormone (GnRH) from hypothalamus stimulating release of FSH and LH
Causes considerable body change
LH from anterior pituitary gland stimulates production of testosterone from the interstitial cells in the testes, which stimulates the development of secondary sexual characteristics
What are the secondary sex characteristics of male puberty
Growth of muscle and bone
Increase in height and weight
Growth of hair on the face,axillae,chest,abdomen and pubis
Enlargement of the penis,scrotum and prostate gland
Maturation of seminiferous tubules and production of spermatozoa
Thickening of skin, becomes oilier
What is spermatogenesis
Process of the formation of male gametes in the testes
In early foetal development primordial germ cells differentiate into spermatogonia
Spermatogonia remains dormant until puberty
Males will develop approx 500 billion sperm in their lifetime with up to 1 billion shed a month
What is spermatozoa
Produced by spermatogenesis in the seminiferous tubules of the testes and mature as they pass through the long and convoluted epididymis where they are stored
FSH can stimulate sperm production
What does a mature spermatozoon have
Has a head, a body and a long whip-like tail used for mobility
Head - almost completely filled by nucleus which contains DNA, as contains enzymes required to penetrate outer layers of the ovum to reach and fuse with nucleus
Body- packed with mitochondria to fuel the propelling action of the tail that powers it along
Explain the head of the sperm
Acrosome- contains enzymes required for penetration of oocyte
Nucleus- contains chromosomes
Explain midpiece of the sperm
Contains mitochondria which supply energy to the sperm
Explain the tail of the sperm
Flagellum to transport sperm
What is the 1st stage of spermatogenesis
Differentiation - primordial germ cell to spermatogonium
Mitosis- spermatogonium to primary spermatocytes
What is 2nd stage of spermatogenesis
Meiosis 1 - primary spermatocyte to secondary spermatocytes
Meiosis 2 - secondary spermatocytes to spermatids
Spermiogenesis - spermatids to spermatozoa
What are the stages of fertilisation
1) sperm deposition
2) capacitation
3) penetration of corona radiata- granules a cells, occurs by acrosome reaction
4) penetration of zona pellucida- glycoprotein layer between corona radiata and oocyte membrane
5) fusion of sperm cell membrane with oocyte cell membrane
6) oocyte competes meiosis 2 ( becomes ovum)
7) gamete fusion ( becomes zygote)
