SS2 Third Term Biology Lesson Note – Reproductive Systems in Vertebrates I

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WEEK 2                                                                                                                                                                                                                                                                                                    

TOPIC: REPRODUCTIVE SYSTEMS IN VERTEBRATES I

CONTENT:

(a) Reproductive systems in bird and mammals

• Structures of the male and female reproductive systems
• Parts of the reproductive systems and their functions
• Structures of the male and female gamete (sperm and ovum)
• Differences between male and female reproductive organs.

SUB-TOPIC 1: REPRODUCTIVE SYSTEMS IN VERTEBRATES.

The male reproductive system of birds (cock) consists of a pair of testis found near the kidneys. A sperm duct runs down from each testis and opens into the cloaca. Sperms cells accumulate at the end of the sperm duct.

As the male cloaca gets in contact in the female during mating, sperm cells are transferred into the female.

A typical female bird (pigeon) has only the left ovary which is located anterior to the kidney. Different sizes of follicles are found in the ovary. The left oviduct is large and wide-mouthed funnel with thick wall and a coiled duct leads into the uvodeum.

Hatchlings

A torrent of food—the result of as many as 1000 daily foraging trips by the parents—helps the chicks of many tree-dwelling birds grow from featherless, blind, helpless nestlings into self-sufficient animals within three weeks. A brood of blue tit chicks is shown here at 3 and 13 days of age, at which time they are fully capable of flight.

The male reproductive system in mammals consists of the following:

The male sex organs are the testis. These are in pairs and are contained in the scrotal sacs, outside the body in order to keep them under a temperature lower than 37⁰C for optimum production of sperms. Sperms are produced in the semimiferous tubules of the testis and are stored in the tubes of the epididymis. The sperms then travel through the sperm duct (vas deferens) to the urethra. Liquid nutrient is added to the sperm from the seminal vesicles and the prostate gland to form the semen. During mating (intercourse), the semen is discharged into the female vagina through the penis.

The female sex organs are called ovaries which are inside the abdomen. These produce eggs which are released into the opening of the oviduct and moved in to the opening of the oviduct and move down the funnel with the aid of the cilia in the oviducal funnel. The oviduct leads to the uterus or the womb. Humans have a single uterus while rats have a double uterus. A fertilized egg is retained in the uterus where it becomes embedded in the wall. The vagina leads from the uterus to the outside of the body. The cervix lies at the end of the uterus and this closes after fertilization to avoid further entrance of sperms and foreign bodies.

EVALUATION

1. What is significant about the testis and ovaries in the reproductive system of mammals?
2. Mention 3 parts of the female reproductive system in birds.

SUB-TOPIC 2:  Parts of the reproductive systems and their functions. Reproductive system of birds and functions of the parts:

Male and Female Birds:

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