SS2 Biology Lesson Note on Reproductive Systems in Vertebrates: Aves and Mammals

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WEEK 2                                                                                                        

TOPIC: REPRODUCTIVE SYSTEMS IN VERTEBRATES I

CONTENT:

(a) Reproductive systems in bird and mammals

• •  (i) Structures of the male and female reproductive systems
  • (ii) Parts of the reproductive systems and their functions
  • (iii)Structures of the male and female gamete (sperm and ovum)
  • (iv) 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 uterus.

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 into 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 sperm 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. The reproductive system of birds and functions of the parts:

Male and Female Birds:

	PART	FUNCTION
1.	Testes	Production of sperm cells. It carries and accumulates sperms, point of transfer of sperms. Point of transfer of sperms.
2.	Ovary, Follicle, and Oviduct	Production of eggs. Contains the immature ovum, and coiled duct that leads into the urodeum.

Some parts of the reproductive systems of mammal and their functions.

The male reproductive system of mammals.

Male Reproductive System

The organs of the male reproductive system enable a man to have sexual intercourse and to fertilize female sex cells (eggs) with sperm. The gonads, called testicles, produce sperm. Sperm pass through a long duct called the vas deferens to the seminal vesicles, a pair of sacs that lies behind the bladder. These sacs produce seminal fluid, which mixes with sperm to produce semen. Semen leaves the seminal vesicles and travels through the prostate gland, which produces additional secretions that are added to semen. During male orgasm the penis ejaculates semen.

1. The Testes: this contains coiled tubules called seminiferous tubules in which actively dividing cells produce the male gametes-sperm cells. The testes also stores the sperm produced in addition to the production of sex hormones- testosterone. This hormone is responsible for the development of male secondary sexual characteristics.
2. Vas deferens: this is the sperm duct which continues from the epididymis. It serves as the pathway through which the sperm run from the epididymis to the urethra.
3. Penis: this is made up of spongy erectile tissue which is a sensitive urinogenital organ. The penis, when erected, discharges semen through the female vagina into the oviduct.

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