Biolgoy 4.1 Sexual Reproduction in Humans

Scrotum

External sac of skin containing the testes

Testes

Produce gametes and testosterone

Epididymis

Sperm are stored here and mature to become fully mobile

Vas deferens

Carries sperm towards the penis during ejaculation

Seminal vesicle

Secretes seminal fluid into the vas deferens

Seminal fluid

makes up approximately 60% of semen

provides nutrients for sperm such as amino acids

Why is seminal fluid alkaline

Helps to neutralise the acidity of any urine remaining in the urethra and the acidity of the vaginal tract

Prostate gland

Secretes prostate fluid into the vas deferens

Prostate fluid

makes up approximately 30% of semen

Prostate fluid contains zinc ions and is also alkaline which helps to neutralise the acidity of any urine remaining in the urethra and the acidity of the vaginal tract

Urethra

Carries semen through the penis and out of the body

Carries urine from the bladder through the penis and out of the body

Penis

Specialised organ adapted to transfer semen to the vagina during sexual intercourse

Ovary

Production of gametes

Produce oestrogen and progesterone

Fallopian tubes

Have a lining of ciliated epithelial cells which move the secondary oocyte to the uterus

Uterus

Holds the developing foetus until birth

Endometrium

The inner most layer of the uterus wall. It has a good blood supply and builds up every month during the menstrual cycle. If implantation of an embryo does not happen then the endometrium is shed during menstruation

Cervix

A narrow ring of connective tissue and muscle

It acts as a barrier between the uterus and the outside environment during pregnancy

During pregnancy, a mucous plug forms in the cervix which helps prevent entry of pathogens

Vagina

It has muscular walls and opens at the vulva
Semen is deposited in the vagina during sexual intercourse and the foetus is able to pass out from the uterus through the vagina during birth

Where does spermatogenesis take place

Seminiferous tubules

Process of spermatogenesis

Germinal epithelium cells divide by mitosis to produce spermatogonia

Spermatagonia divide many times by mitosis and increase in size to form primary spermatocytes

Primary spermatocytes undergo meiosis to form secondary spermatocytes

Secondary spermatocytes undergo meiosis to form spermatids

Spermatids mature and differentiate into spermatozoa

Sertoli cells

provide nourishment for spermatids and

protection against the male's immune

system

What surrounds the seminiferous tubule

Basement membrane of connective tissue

Interstitial cells

Secrete testosterone which

stimulates spermatogenesis

Acrosome

Contains protease enzymes

Mitochondria of sperm

Spiraled around microtubules