Starter1. Testosterone is an important

male hormone. 

Describe where and when testosterone is produced.

Describe TWO roles of testosterone in the male body.

Starter

A)

B)

C)

D)

2

Starter3. Explain how blocked sperm ducts

affect sperm and can cause infertility in men.

Sperm cannot travel from testes /epididymis to penis so the semen / ejaculate contains no sperm/sperm cannot get into vagina.

ORVery few sperm so chances of sperm

reaching egg very unlikely.

Fertilization

FertilizationFertilization is the fusion of the sperm and egg nuclei to form a zygote.

This process is more a chain of events rather than a single, isolated phenomenon.

FertilizationBefore fertilization can occur there must be intercourse.

The penis is inserted into the vagina where movement stimulates ejaculation.

FertilizationDuring this process sperm that have been maturing in the epididymus are propelled down the vas deferens by contractions of muscles in the walls.

At the same time the prostate and seminal vesicles contract adding semen to the sperm.

Role of SemenThe prostate gland secretes an alkaline fluid that will neutralize the acidic environment of the vagina.

The seminal vesicles produce fructose used by sperm in respiration by the large number of mitochondria (behind the sperm head) provides sperm with source of energy to swim the distance from the vagina to oviduct.

FertilizationAbout 200-300 million sperm are released at the point of ejaculation.

When ejected, they 'swim' through the cervix into the uterus propelled by their thread-like tail.

FertilizationThe sperm swim through the uterus where 99.99% are destroyed on their way to the fallopian tubes.

Usually fewer than 100 sperm reach the oocyte approximately 10-15 cm away from their release point.

Fertilization

FertilizationAcrosomal Enzymes from the sperm are

released and the membrane of the ovum begins to break down.

A single sperm will enter the egg and the 2 haploid nuclei fuse together to form a diploid zygote.

Within seconds of entry the membrane of the egg changes and prevents other sperm from entering.

Hormones at Fertilization When fertilization occurs the corpus luteum does not deteriorate.

It continues to produce oestrogen and progesterone which build the blood vessels in the endometrium in preparation for implantation.