Lesson Note

Subject: Agricultural Science

Topic: Reproductive System in Mammals And Poultry

Class: SS2

Lesson Objective: by the end of the lesson, the learners should be able to:

  1. Explain the role of sex hormones in reproduction;
  2. Draw and label the parts of the male and female reproductive systems;
  3. Explain the process of reproduction in mammals and poultry;
  4. Describe the process of egg formation in poultry.

Lesson Summary/Discussion


Reproduction is the ability in animal to give birth to young ones. The purpose of reproduction is to ensure continuity of life.
The reproductive system includes all the organs and tissues concerned with reproduction in animals.

Farm animals reproduce sexually and
are mostly viviparous because they bear their voung ones alive. Poultry birds on the other hand are oviparous because they produce their young
ones by hatching eggs after an incubation period.


The reproductive system includes all the organs and tissues concerned with reproduction in animals. Reproduction is the ability in animal to give birth to young ones. The purpose of reproduction is to ensure continuity of lite.
Farm animals reproduce sexually and
are mostly viviparous because they bear their young ones alive. Poultry birds on the other hand are oviparous because they produce their young
ones by hatching eggs after an incubation period.

Male Reproductive System (Mammals)
The male reproductive system includes the testes which produce the
spermatozoa and sex hormone called
testosterone which aids the development of male sexual secondary characteristics. The
spermatozoa are specifically produced in the seminiferous tubules of testes during meiotic cell division by a process called spermatogenesis.
The testes are suspended or protected by scrotal sac (scrotum) outside the abdominal cavity to enable sperm cells to be produced at desired temperature.

The Male Reproductive System

The epididymis ensures the storage and maturation of sperm cells in the testes. The testes are connected to the uterus masculinus by vas deferens which transports sperms from testes
to the uterus masculine where matured spermatozoa are stored until they are released during coitus or mating. Blood vessels called spermatic cord supply nutrients and oxygen to the testes. Located along the urethra are accessory glands which are the Cowper’s gland, seminal vesicle and prostate glands. They produce slimy alkaline fluid which aids the movement of spermatozoa. This fluid together with the spermatozoa results in the formation of semen. The urethra is a uro-genital organ which helps to inject sperms into the vagina as well as the removal of urine. The urethra ends externally in penis.

Female Reproductive System (Mammals)

The female reproductive system includes the ovaries which produce the ovum or ova (eggs) enclosed by the graffian follicles and some hormones such as the oestrogen.

A matured egg or ovum is released from the follicle in the ovary into the oviduct. This process is called ovulation.
As the ovum or egg is released from the ovary, the female animal comes into heat and is Willing to mate with the male animal.

Female Reproductive System

Fertilisation, which is the fusion of the male sex cell (spermatozoa) and the female sex cell (egg or ovum) takes place in the fallopian tube or the oviduct. When the egg is fertilised by the spermatozoa, the fertilised egg anchors itself to the wall of the uterus. This process is called implantation. The development of the foetus takes place in the uterus. Below the uterus is the vagina which receives the spermatozoa during corpulation. The female reproductive system terminates with an external opening called the vulva.

Development of the Embryo (Foetus) in Mammals

The fertilised egg is implanted in the uterus where the development of the embryo takes place. Soon, a number of embryonic membranes develop round the embryo. These are: the chorion, the allantois and the yolksac.
The amnion forms a sac in which the embryo lies and is filled with amniotic fluid. Hence, the embryo is held in a liquid environment which acts as a buffer or “shock absorber“. This ensures the protection of the embryo. The allantois forms a sac which is excretory, respiratory and nutritive in function. It contributes to the formation of placenta. The yolk sac provides the food during the early stages of embryonic development. The chorion forms the outermost membrane, enveloping all these

Developing Embryo

The placenta establishes an intimate
connection between the embryo and the mother which aids nutritional, respiratory and excretory needs of the embryo (foetus). The placenta and
the embryo are connected by the umbilical cord which develops from the allantois. The parental blood supply is linked to the foetal blood supply through this umbilical cord.

At the end of the gestation period (from fertilisation to birth), parturition (giving birth) takes place during which the young animal is pushed out through the vagina. The remaining part of the embryonic membrane known as after-birth is sent out after the birth of the foetus.


Male Reproductive Hormones
Androgen (Testosterone)

  • It initiates spermatogenesis (sperm formation)
  • It is responsible for the initiation of male secondary sex characteristics
  • Maintains the sex drive (libido)
  • Enhances muscular and skeletal growth
  • Reduces fat deposition
  • Promotes the growth of accessory sex glands.
  • Sustains the life of sperms in the epididymis.

Female Reproductive Hormones
Stimulates the development of female secondary sex characteristics e.g. heat behaviour.

  • Promotes the production of eggs through oogenesis.
  • It is concerned with the preparation of the uterus lining for the reception of the fertilized ovum.
  • It inereases blood supply as well as the water content of the uterus
  • It stimulates the growth of the duct system in the mammary glands (udder in the oviduct, it increases cilliary activities and mucous secretion.
  • Induces the rapid multiplication of epithelum in the vagina

Follicle Stimulating Hormone (FSH)

  • It stimulates the growth of the ovarian follicle.

Luteinizing Hormone (LH)

  • It causes the rupture of the follicle and subsequent release of ova (i.e ovulation)
  • It stimulates the secretion of ovarian hormones i.e. oestrogen and progesterone.
  • Progesterone (Pregnancy hormone)
  • It ensures the development of uterus and implantation of the fertilised ovum.
  • It inhibits oestrus (i.e it prevents the ripening of more follicles).
  • It causes the development of alveoli in mammary gland.
  • It ensures the continuance of pregnancy.


  • It aids in the contraction of the female uterine muscles during pregnancy.
  • It affects mammary gland after birth by causing milk let-down or milk production.
  • It promotes the transport of spermatozoa in the female genital tract.


  • It causes the relaxation of the pelvic ligament during parturition for easy passage of the young ones.

Reproductive Systems in Birds
In the male bird, the two testes are located inside the body. A narrow tube connects them to the cloaca in which the tube ends as a small raised papilla.
In the female, only the left ovary is
functioning. The single ovary produces ova (eggs) in capsules attached to the ovary by short stalks. The ovary also produces the yolk.

Reproductive System of Birds

The infundibulum receives the yolk
released by the ovary. Albumen and chalazia (which hold the yolk and germ cell in position) are formed in the magnum. The two shell membranes and the shape of the egg are formed in the isthmus. The egg shell is finally formed in the uterus after which the egg is laid through the cloaca. Fertilisation of the egg can take place as soon as the egg enters the oviduct when spermatozoa are present. Fertilization occurs before the formation of the albumen.

Functions of the Reproductive System

  1. It ensures the continuity of species by gamete for motion, coitus, mating or servicing.
  2. It ensures the formation of eggs and spermatozoa (sperm cells).
  3. It ensures the production of reproductive hormones.


The process of egg formation is controlled by hormones. The egg is formed partly in the ovary and partly in the oviduct.
Ovary: The yolk is secreted by the ovary and enclosed in a follicle. The yolk increases in size by accumulating yolk materials carried from different parts of the body by blood stream. The germinal disc is attached to the top of the yolk.
The follicle bursts to release the yolk.
Infundibulum: The yolk released by the ovary is taken up by the infundibulum, the internal terminal part of the oviduct. Fertilization of the
egg occurs in this part of the oviduct, before the other components are added. However complete formation of the egg is independent of whether the egg is fertilised or not. The egg
spends 15 minutes in the infundibulum before it moves to the magnum.

Magnum: In the magnum, the egg stays for three hours and part of the albumen is secreted on the yolk. Chalaza is also formed in this region
The egg now moves to the isthmus.
Isthmus: The egg stays here for 75 minutes and the two shell membranes are formed. The shape of the egg is also formed at this region after which it moves to the uterus.

Uterus: The egg stays here for 19-20 hours where the shell is formed from calcium carbonate secreted by glands of the uterus. Mineral solutions are also added to the egg after which
it moves to the vagina.
Vagina: The egg stays here for a very short time before it is laid through the cloaca or vent. It takes almost 26 hours for a complete egg to be formed and laid.

Structure of a Fertile Egg
Shape: The egg is oval or oblong in shape. It is either brown or white in colour. The differences in colour are due to differences in breeds.

Membranes: Immediately after the outer shell are outer and inner membranes. Both membranes give protection to the egg.
Airspace: The airspace is located on one of the pointed ends of the egg. It is found in-between the outer and inner membranes. The airspace is very important for respiration of the embryo.

Structure of an Egg

Albumen: This is also called the egg white. It accounts for over 50% of the total body weight of the egg. It is rich in protein.
Yolk: This is located at the centre of the egg. It is a yellowish jelly-like mass. It is rich in proteins, mineral salts, vitamins and other food substances. It supplies the embryo nutrients.
Embryo: This is also called germinal disc. This is located at the centre of the yolk as a dark spot. The germinal disc is only found in fertile eggs. It develops to form the chick during incubation period.

Chalaza: The chalaza extends to both sides of the yolk. It is a piece of thick protoplasm. It holds the yolk and the embryo in place within the albumen.

See previous lessons in Agricultural Science

Lesson Evaluation/Test

  1. What is reproduction?
  2. Lis the sex hormones and their role in reproduction.
  3. Draw and label the parts of the male and female reproductive systems.
  4. Explain the process of reproduction in mammals and poultry.
  5. Describe the process of egg formation in poultry.

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