Consists of:

• A pair of testes contained in an external sac, the scrotum.
• The penis
• Ducts containing the testes with the penis
• Accessory glands e.g - a pair of seminal vesicles and the prostate gland. These glands secrete fluids that mix with the sperm to make seman.

The secretions of the accessory glands are alkaline and they:

• Maintaining sperm mobility
  
  
  

• Provide nutrients for the sperm, including frutose, their main energy source, amino acids and zinc ions
  
  
  

• Nutralise the acidity of any urine remaining in the urethra
  
  
  

• Neutralise the acidity of the vaginal tract.

• Two ovaries
  
  
  

• Oocytes (eggs) mature in the follicles, which develope from the cells in the germinal epithelium, around the periphery of the ovary.
  
  
  

• Mature follicles migrate to the surface of the ovary, from where a secondary oocyte is released at ovulation.
  
  
  

• Ovaries alternate each month in releasing the oocyte.

Uterus wall has three layers

• The perimetrium is a thin layer around the outside
• The myometrium is the muscle layer
• The endrometrium is the innermost layer. It is a mucous membrane, which is well supplied with blood. It is a layer that builds and is shed in the monthly cycle, unless an oocyte is fertilised, in which case, the embryo implants in the endometrium, establishing a pregnancy

• The uterus opens into the vaginal wall through a narrow ring of connective tissue and muscle, the cervix. The walls of the vagina are muscular and open at the vulva.

• The production of gametes in the sex organs is called gametogenesis.

  
  

• Spermatogenesis is the formation of sperm in the testis. Oogenesis is the formation of secondary oocytes in the ovary

• The cells of the germinal epithelium of both testis and the ovary undergo a sequence of mitotic and meiotic divisions to form haploid gamete. It is important that the gametes are haploid so as fertilisation the diploid number is restored and the chromosome number doesn't double in every generation

• Cells of the germinal epithelium are diploid. They divide mitosis to make diploid spermtogonia and more germinal epithelium cells.

• The spermatogonia divide many times by mitosis, making more spermatogonia. Some enlarge, making more diploid primary spermatocytes.

• Primary spermatocytes undergo meiosis I, making secondary spermatocytes, which are haploid.

• Secondary spermatocytes undergo meiosis II, making haploud spermatids.

• Spermatids mature into spermatozoa or sperm.

Sperm Structure

• The head containing a haploid, covered at the anterior end by lysosome, called acrosome, which contain enzymes.
  
  
  

• The middle peice is packed with mitochondria, which provide ATP for movement. The spiral around microtubiles, which extend from the centrioles into the axial filament in the tail.
  
  
  

• The tail, or flagellum, makes lashing movements that move the sperm, although sperm are not motile until they have been modified in the epidiymis

• Before birth, in the foetus, cells of the germinal epithelium of the ovary, which are diploid,
• Divide by mitosis to make diploid oogonia, and more germinal epithelium cells

• The oogonia divide many times by mitosis and enlarge, making diploid primary oocytes and more oogonia

• The primary oocytes begin meiosis I but stop; a girl is born with millions of primary oocytes at prophase I in her ovaries.

• Germinal epithelium cells divide to form diploid follicle cells, which surround the primary oocytes, making primary follicles.

From puberty onwards:

• Hormones stimulate the primary follicles to develop further.
• Just before ovulation, a primary oocyte completes meiosis I, making a secondary oocyte, which contains most of the cytoplasm.
• The other product of meiosis I is a much smaller cell, it extrudes from the end of the secondary oocyte, and so it is called the first polar body. It usually disintegrates
  immediately, but occasionally divides first. The secondary oocyte and polar body are both haploid.

• The primary follicle develops into the secondary follicle, which is called a Graafian Follicle when its mature.
• Graafian Follicle migrates to the surface of the ovary where it bursts and releases the seondary oocyte, in the process called ovulation.
• Each month several primary follicles start to develop but normally, only one matures into a fully developed Graafian Follicle

• The secondary oocyte begins meiosis II but stops at metaphase II unless fertilisation takes place

• After fertilisation, meiosis II is completed, making an ovum containing most of the cytoplasm. The other product of meiosis II is the second polar body

• After ovulation the Graafian follicle become the corpus luteus
• If fertilation occurs, it produces hormones but otherwise, regresses.
  

1. Several sperm cluster around the ovum. One penetrates the Zona Pellucida (waxy laer) of the ovum (egg cell)
   
   
   

2. This triggers the acrosome reaction. The acrosome bursts and the zona pellucida and follicle cells are digested
   
   
   

3. Membranes fuse, and the haploid spermatozoa nucleus enters the egg cytoplasm.

4. This triggers the cortical reaction. The cortical granules fuse with the cell membrane and release their contents via exocytosis into the zona pellucida. The zona pellucida hardens and thickens. Ion channels open/close to change across the membrane. This makes the egg cell impermeable and prevents polyspermy

5. Meiosis II takes place and the secondary oocyte matures into an ootid and then a mature ovum (takes only a few minutes)

6. The chromosome combine to form a diploid zygote

• Menstruation, birth and lactation are controlled by endocrine glands - glands which secrete hormones directly into the bloodstream.

Day 1 - Menstruation

• Oestrogen and progesterone levels are low. This causes the utuerus to shed its lining, causing menstruation. The unfertilised egg also passes out during this phase.

  
  

• Levels of follicle-stimulating hormone produced by the pituitary gland increase. This stimulates the growth of several follicles in the ovary. Each follicle contains a ovum.

  
  

• Follicles secrete oestrogen, as oestrogen levels increase, this supresses the growth of any more follicles.