INTRODUCTION ABOUT REPRODUCTIVE SYSTEMS

INTRODUCTION ABOUT REPRODUCTIVE SYSTEMS

Reproduction is the production of new individuals from the older ones of the same species. The organs concerned with reproduction are called reproductive organs. The male reproductive organ is the testis while the female reproductive organs. The male reproductive organ is the testis while the female reproductive organ is the ovary.

REPRODUCTIVE SYSTEMS OF MAMMALS

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THE MALE REPRODUTIVE SYSTEMS OF MAMMALS

In mammals, there are two oval_ shaped tests which are located houses the two testes. Each testis is made up of highly coiled tubules called the seminiferous tubes. The tubules unite to form a much coiled tubules called the epididymis and is about six metre long.
The epididymis lying outside each testis, leads into a muscular sperm duct ( vas _ deferens). The two vas deferentia, one from each testis come together and open into the top of the urethra which is continuous with the urinary bladder. A short coiled tube, the seminal vesicle branches from each sperm duct also opens into the origin of the urethra. Near this origin of the urethra is situated a prostate gland. Just below it, on either side of the urethra, lies the Cowper's gland. The urethra is a narrow tube that prolonged in the erectile organ, the penis.

FUNCTION

(1) SCROTUM: A bag or sac that houses and protects the testes. It also encourage s sperm production by Lowering testes' temperature.

(2) TESTIS: The cells of seminiferous tubules of the testes produce sperms.

(3) VAS DEFERENS: A dust for conducting sperms to urethra.

(4) SEMINAL VESICLE: Secretes a fluid (semen in which sperms are suspended.

(5) PROSTATE GLAND: It secretion activities the sperms.

(6) COWPER'S GLAND: Secretes lubricant and acid neutralizer into the urethra.

(7) URETHRA: Passage of sperm and urine to the outside and so it is said to be urinogenital in function.

(8) PENIS: For introduction of sperms into the vagina.

THE FEMALE REPRODUTIVE ORGAN IN MAMMALS

RABBIT

The two ovaries are located below the kidneys. Close to each ovary is the oviductal funnel, leading into the fallopian tube or oviduct. The fallopian tubes or oviducts are narrow tubes that lead down into a wider paired tube called uterus or womb. The two horned uteri finally join up to form vagina. The narrow lower end of the uteri which Lea into the vagina is the cervix.
The urthra opens into the vagina to form a common passage the vestibule. This serves as the urinogenital tract which has an opening through vulva.

HUMAN

In human, the two of ovaries are located below the kidneys. Close to each ovary is a funnel shaped structure, the fallopian funnel which leads into narrow duct called the oviduct or fallopian tube. The tube leads into one common uterus or womb which subsequently opens into the vagina. The lower narrow end of the uterus which leads into the vagina is cervix. The vagina open to the outside through the vulva.

FUNCTIONS

(1)OVARY: The graafian follicle of ovary produces ovum.

(2) OVIDUCT OR FALLOPIAN TUBE: Passage of released eggs and site fertilization.

(3) UTERUS: Where fertilized eggs develop.

(4) VAGINA: For copulation, deposition of the sperms and for the passage of a baby during birth.

DIFFERENCES BETWEEN MALE AND FEMALE REPRODUCTIVE ORGANS IN MAMMALS

MALE (TESTIS). FEMA_
LE(OVARY

(1) Testes are in scrotal. Ovaries
Sac outside the body. are within
the body.

(2) Testes produce Ovaries
Sperms. Produce
Ova or
Eggs.

(3) Erectile organ Erectile
Is penis. Organ is
Clitoris.

(4) Epididymis is Epididymis
Present. Absent.

(5) Seminal vesicle Seminal
present. Vesicle
Absent.

(6) Oviduct absent. Oviduct
Present.

(7) Cowper's gland Cowper's
Present. Gland
Absent.

(8) Sperms pass out Ova pass
Through the urethra. Into the
Oviduct.

(9) Cervix absent. Cervix
Present.

(10) Prostate gland Prostate
Present. Gland
Absent.

(11) Vulva absent. Vulva
Absent.

(12) Sperm production Ovum or egg
Is continuous. Production
is periodic.

(13) Hormone of testis Hormone of
Is testosterone. the ovary is
oestrogen.

COMPARISON OF REPRODUCTION VERTEBRATES

FISH

In fishes, fertilization is external except in some bony fishes like the Guppy in which it is internal. They lay vast number of eggs some times up to a few millions to ensure fertilization. They do not show any parental care for their youngs ( either for the eggs or for the young ones in their earlier stages). The developing embryos feed from yolk hence they do not have placenta. The development of their young ones is external ( oviparous) but in some fishes like Guppy, the development of their eggs into young fishes is internal. Fishes of this sort are to be ovoviviparous, while those that lay eggs are oviparous.

AMPHIBIANS

In amphibians, the fertilization is external. The developing tadpoles feed freely on their own without parental care. Placenta is absent in amphibians since the tadpoles are independent of their mother. The development is external or oviparous. They lay many eggs to ensure fertilization since it is external.

REPTILES

In reptiles, the fertilization is internal. They lay many eggs with shells. The development of their into young ones is mainly external or oviparous. Very few reptiles do not lay eggs but give birth to well_ developed young ones hence are viviparous. The developing embryo feeds from the yolk. Placenta is absent. They do not show parental care for the young ones except in Nile crocodiles.

BIRDS

Fertilization is internal and occurs as soon as the large yolky egg cell is released. They lay few eggs since they care for them and internal fertilization is sure. The developing embryo in the eggs, feeds from the yolk, albumen and shell. Placenta is absent. The development of embryo into a chick is external. Birds show parental care for their young ones by feeling, guarding and brooding them until they are able to fly and to fend for themselves.

MAMMALS

Fertilization in mammals is internal. They produce few eggs and few young ones since fertilization and survival of young ones are surer. The development of their young ones is internal hence viviparous. Feeding of foetus is through the placenta. Mammals show very high parental care for their young ones.

REPRODUCTIVE SYSTEMS IN PLANTS

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A flower is an organ of sexual reproduction in a plants.

FUNCTIONS

The floral parts of a flower ( modified leaves ) are the calyx, Corolla, androecium and gynoecium.

(1) CALYX: It consists of sepals and protects the flower in the bud. Coloured sepals are called petaloid while free sepals are described as polysepalous, and fused as gamosepalous.

(2) COROLLA: Made up of petals which are often brightly coloured and scented to attract insects. It also protects the stamens and carpels. Green petals are described as sepaloid while sepals and petals that look alike or fused together are known as perianth. Free petals as in pride of Barbados are described as poly_ petaious while fused petals are described as gamosepalous.

(3) ANDROECIUM: It is the male reproductive organ. It is made up of stamens. Each stamen is made up of stall called filament and an another attached to it. The filament holds the another in position. The anthers consists of pollen sacs which consists the pollen grains containing male sex cells or male gametes. Thus pollen grains are similar to sperms in animals.

(4) GYNOECIUM: This is the female part of the flower. It consists of one or more carpels or pistils, Each carpel consists of the ovary, ovules in the ovary and a style. The carpels may be free ( apocarpous) , eg. Bryophyllum and rose flower, or fused ( syncarpous) , eg. Hibiscus.

FUNCTION OF GYNOECIUM

(1) Stigma receives pollen grains and also nourishes the pollens to germinate.

(2) The style is passage way for germinating pollen grain or pollen tube to reach the ovule.

(3) The ovary houses the ovule and also develops to fruit.

(4) The ovule develops to seed after fertilization and

(5) The placenta connects ovule
Or seed to the ovary for nourishment.

THE ESSENTIAL PARTS And NON_ ESSENTIAL PARTS OF A FLOWER

(1) Essential parts are the ANDROECIUM and GYNOECIUM.

(2) Non_ essential parts are the calyx and Corolla.

TYPES OF FLOWERS

(1) HYPOGYNOUS: A flower is hypogynous. If all the floral parts are above the receptacle. eg. mango.

(2) PERIGYNOUS: The receptacle is cup_shaped and the sepals.petals and stamens are arranged at its margins with the ovary in its centre, eg. cassia.

(3) EPIGYNOUS: The receptacle forms a complete ring round the ovary with the result that the sepals are above the ovary.

(4) HERMAPHRODITIC: It is a flower with both male and female parts. eg. Pride of Baroados.

(5) UNISEXUAL FLOWERS: They are flowers with pisses either stamens or carpels. eg. Pawpaw.

(6) STAMINATE AND PISTILLATE FLOWERS: A male flower is known as a staminate flower and a female flower as a pistillate one.

(7) MONOECIOUS: Both male and female flowers are borne on the same plant. eg. Oil palm and maize.

(8) DIOECIOUS: When plants bear either male or female flowers only, eg. Pawpaw, date palm.

(9) REGULAR OR ACTINOMORPHIC: Flowers that can be divided into two similar halves by any vertical section passing through the centre hence radially symmetrical, eg. Morning glory.

(10) IRREGULAR OR ZYGOMORPHIC: Flower that can be divided into equal halves in one particular plane only, eg. Crotalaria.

PLACENTATION

Placentation is the arrangement of the ovules and the placentae within the ovary.

(1) MARGINAL: The ovules are arranged along the joined edges of a single carpel, eg. Flamboyant and Crotalaria.

(2) PARIETAL: The ovules are arranged along the walls of a synacarpous ovary. eg. Pawpaw.

(3) AXILE: The ovules are arranged at the central axis formed by a syncarpous ovary, eg. tomato.

(4) FREE _ CENTRAL: The ovules are borne on a knob which projects from the base of the ovary, eg. water leaf, pear, pepper.

REFERENCE

Introduction to the Reproductive System, Epidemiology and End Results (SEER) Program. Archived October 24, 2007, at the Wayback Machine.

Reproductive System 2001 Body Guide powered by Adam.

Sexual Reproduction in Humans. 2006. John W. Kimball. Kimball's Biology Pages, and online textbook.