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tL —————, , Sr. No, , 1.1,, , 1.2., , 13., , 1.4., 1.5., , 1.6., , 2.1:, , 2.3, , Contents, , Chapter, , Unit 1: Comparative Embryology, , Introduction, , Types of eggs: based on amount and distribution of yolk, 1.1.1, Classification of eggs based on amount of yolk, 1.1.2. Classification of eggs based on distribution of yolk, 1.1.3. Mosaic and regulative eggs, , Structure and types of sperms, 1.2.1. Basic structure of sperm, 1.2.2. Types of sperms in animals, , Types of cleavage: Holoblastic and Meroblastic, , 1.3.1, Holoblastic cleavage, 1.3.2. Meroblastic cleavage, , Types of blastulae, , Gastrulation, 1.5.1. Morphogenetic Movements, , Coelom- formation and types, 1.6.1. Formation of Coelom (Schizocoely and enterocoely), 1.6.2. Types of Coelom, , Extra embryonic membranes and Types of plancentae, 1.7.1. Extra embryonic membrane, 1.7.2. Types of placentae- based on histology, morphology and, implantation, , Unit 2 : Aspects of Human Reproduction, , Human Reproductive system and Hormonal regulation, 2.1.1. Anatomy of human male and female reproductive system, 2.1.2. Hormonal regulation of Reproduction, 2.1.3. Impact of age on reproduction - Menopause and Andropause, , Contraception & birth control, 2.2.1. Difference between contraception and birth control, , 2.2.2. Methods of contraception - Natural methods and Artificial, methods, , Infertility, 2.3.1. Female infertility, 2.3.2. Infertility associated disorders, , Page Nos., , 13, 13-17, 14, 15, 16, , 17-19, 18, 19, , 19-23, , 20, 22, , 23-24, 25-30, , 30-32, , 51-55, 51, 51, , 55-60, 56, 58
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CHAPTER - 1, , COMPARATIVE EMBRYOLOGY, , Objective : Toacquaint the leamer with key concepts of embry 0108, , he different pre- embryonic, , mpare t ic, ; sg of extra embryonic, , functional aspect, of placentac., , Desired Outcomes : Leamer will be able to understand and co, stages. Leamer will be able to appreciate the, membranes and classify the different types, , Introduction:, , Like growth, metabolism and irritability, reproduction is one, Reproduction is the process of multiplication of individuals in, ensures the form and function ofan organism. Animals have adapted for the mu, with the process of reproduction. Reproduction is basically classified as asexual a -., sexual reproduction involves gametogenesis (formation of sex cells or gametes like sperms and ova germinal epithelium of testis and ovary respectively), fusion of gametes (fertilization), egg formation art, , the embryonic development (zygote transformations). Development of embryo plays very important role, jay important role to know the, , in reproduction. Also it is known that the embryonic development pl 2, evolutionary tract of the species (ontogeny repeats the phylogeny). Based on the embryonic evidences, animals are classified into protostomes and deuterostomes. Protostomes are inclusive of invertebrates, which develop mouth from blastopore (poriferans to molluscans) whilst the deuterostomes develop mouth, opposite to blastopore by forming separate opening and blastopore develops into anus (echinoderms, onwards). The higher vertebrates are further classified into anamniotes and amniotes as they do not or, , do have the extraembryonic membrane known as amnion respectively., , of the properties of the living organisms., , the population belonging toa species. It, [tiplication and their survival, , and sexual types. The, , 1.1. Types of Eggs: Based on Amount and Distribution of Yolk, , ted to reproduce in aquatic medium which is best suited for their, evolution. With the evolution the higher forms, like amniotes, dto live in dry terrestrial environment. However, in terrestrial, , animals, who have internal fertilization but the external development of embryo (outside the body of, , mother), their ova get transformed into shelled eggs which carry huge amount of yolk. In placental animals, Je amount since the embryo is nurtured through feto-maternal association of, , the yolk is present in negligib!, , tissue called placenta. Although yolk is an essential food reservoir playing important role in development, , of the embryo, it has been observed that it causes the polarity in the egg and hinders the development of, osition of yolk is therefore known as vegetal pole and on opposite side, , embryo. The area of heavy dep, with nucleus and concentrated cytoplasm is knownas animal pole (Fig. 1.1). The animal pole inside the, eggis vital end where metabolism takes place for the embryonic development., , The primitive aquatic forms have adap, embryonic developments in due course of, (reptiles, birds and mammals), have adapter, , Polar body, Animal hemisphere, -Vitelline membrane, , , , , Grey crescent, , Vegetal hemisphere, , Figure 1.1: A schematic diagram showing animal and vegetal poles of polarized egg of frog., , 13
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Dependent on the adaptive radiation, animals have developed various methods of reproduction. The, development of ova or egg is not an exception, The ova and eggs, by and large, are commonly referred as, ‘eggs’ and are classified into categories further based on the amount and allocation of yolk within the egg, , , , Classification of eggs of animals based on, amount and distribution of yolk, , , , , , , , [Based on & stiibution of york |, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , [Based on amount of yor], Oligolecithal egg Polylecithal egg Isolecithal egg ‘ Tololect Centrolecithal exe, Egg. containing smal Pe ere es we, amount of yo, Urge aeruen of yolk, tro agg), non, , Alecithal eggs Mesolecithal ege cerns eaelantarater, Reg Comrateing fo YOR Egg contsterg moderate amount of yolk., , Example: Eutherlans Examples: Petroenyron, dipnot, amphibians., -Microlecithal [, , : ieee ar Macrotecithal or Megalecithal ege | [ Slightly Moderstely Pronounced, , We ~ ey Fag contavning very large amour of yolk. telolecithal telolecithal telolecithal, Examples: Exampioa: bay fish, senptyibiens, reptile Enarere: Fish, Enaerghe: Amphibran Example: Rectiles wed, AmpNouus, tuncates and birds, Leos, , , , , , , , , , , , , , Figure 1.2 : Classification of eggs on the bases of amount and distribution of yolk., , 1.1.1. Classification of eggs based on amount of yolk, , Based on the amount of yolk present, the eggs are classified into two major groups as oligolecithal and, polylecithal eggs which are further subdivided into alecithal, microlecithal, mesolecithal and macrolecithal, , (megalecithal) respectively., , A., , Oligolecithal Eggs:, Oligolecithal eggs contain negligible amount of yolk and hence they are not capable of complete, , development of embryo and are subjected to undergo several metamosphic stages like larvae, pupae, and instars (invertebrates) or they acquire the support of mother by forming placenta (mammals) for, , further development. :, These types of eggs undergo holoblastic cleavage since there is no hindrance due to yolk., , i, Alecithal Egg, Alecithal egg is characterized by its negligible amount of yolk. In such a case the embryo needs, , to be implanted immediately after fertilization to form placenta, Placenta is a union of matemal, and foetal tissues formed inside the uterus of mother for the exchange of gases and nutrients so, as to execute complete development of the embryo e.g. Eutherians (placental mammals)., , Eutherians therefore show direct development., , ii, Microlecithal Egg |, . contains very little and mostly evenly distributed yolk. e.g, insects, Amphioxus, , This type of egg, , dtunicates. Therefore in insects the development is indirect and embryo undergoes stages, ani ., , i ichi ed extensively to acquire the energy essential for, t like larva which is allowed to feed extensive ye, ata ment known as metamorphosis. Tunicates also forma short living tadpole, fa a fis aie into an adult. While in Amphioxus the development undergoes rapidly, - larva be! ;, to cope with the meager yolk reserve in the egg., 14
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___, , Polylecithal Eggs:, , Generally yj, Y OViparous ani . 3 k enough, for the Complete dey, ‘nals produce Polylecithal eggs. These eggs are heavily laden with yol, , and Macrolecithal t, , i,, , clopment of the e olecithal, , rypes. mbryo before hatching. They are further classified as mes!, , Mesolecithal Egg, , This type of, gg contains moder. his largely confined to vegetal pole., , Ani ‘ate amount of yolk whic i, b nimal pole has cytoplasm and nucleus. The mesolecithal eggs undergo Se Lae ee, ut comparatively slo, , Pa ; Wer, particularly in vegetal pole, than that of microlecithal eggs ¢.g., myzon, Dipnoi (lungfish) and amphibians., , Macrolecithal Egg, , Macrolecithal or megalecithal egg contains large amount of yolk. Terrestrial animals like es, birds and Some mammals lay eggs with huge amount of yolk. This ensures a complete a °, embryo inside the egg itself before ithatches out. Due to the large amount of yolk the cleavage, , is of meroblastic type e.g. bony fishes, amphibians, reptiles and birds and monotremes (egg, laying mammals),, , 1.1.2. Classification of eggs based on distribution of yolk, , As the eggs of animals store different amount of yolk, there is a variation in its distribution in the egg, proper. Microlecithal eggs show even distribution of the yolk while in the macrolecithal eggs it may be, , pushed to one end. Depending upon the distribution of yolk, the eggs are classified as isolecithal, telolecithal, and centrolecithal., , A., , Isolecithal or homolecithal Egg : :, Isolecithal eggs contain very little amount of yolk which is distributed uniformly in the cytoplasm., These eggs undergo holoblastic cleavage e.g. echinoderms, Amphioxus, mammals etc., , Telolecithal Egg : /, The eccentric distribution of yolk defines themas telolecithal eggs. These eggs contain very high, amount of yolk usually concentrated at the vegetal pole. ‘Therefore the telolecithal eggs show, pronounced polarity. The vegetal pole is large and prominentin telolecithal eggs; hence cleavage is of, meroblastic type (partial). These eggs are further sub-divided as slightly telolecithal, moderately, , telolecithal or pronounced telolecithal type., , i), , ii), , iii), , Slightly telolecithal egg: It has small quantity of yolk which is distributed unevenly. The vegetal, , hemisphere has the highest coricentration and the animal hemisphere the lowest e.g. eggs of, -fisties-Tn this case nucleus is placed in the centre. e.g. eggs of fishes. oa, , Moderately telolecithal egg: It contains a moderate quantity of yolk which is, distributed unevenly. Due to high concentration of yolk in the vegetal hemisphere, the nucleus is, , $hified more towards the animal hemisphere e.g. egg of amphibian., , Pronounced telolecithal egg: In this type of egg, due to the heavy deposition of yolk, the, entire vegetal hemisphere and a major portion of the animal hemisphere is occupied by yolk., , Dueto this extremely uneven distribution of yolk, the ooplasm and nucleus are displaced towards, the animal pole e.g. egg of reptiles and birds., , 15
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C. Centrolecithal Lge, The centre of the egg is occupied by nucleus and a small amount of cytoplasm which is Covered by a, , thick layer of yolk. At the periphery the yolk is surrounded bya thin layer of cytoplasm which is, Connected by fine strands of cytoplasm to central vital part e.g. arthropods and some coelenterates., , , , Alecithal egg Mikrolecithal ege Masolecithal agg, Matrolecithal ogg, , Classification of eggs based on amount of yolk, , Strand of cytoplasm, , , , Isotactthal egg Tetotecithal egg Cantrolecithal agg, , , , Slightly telobecithat Moderately telotecithal Pronounced telotecithal, , Classification of eggs based on distribution of yolk, , , , , , , , , , @ Nucleus Cytoplasm “Jr t] yolk granules in, —J the cytoplasm, , , , , , , , , , , , , , , , | bonse yotk, , , , , , , , Figure 1.3: Diagrammatic representation of classification of eggs on the bases of amount, and distribution of yolk., , 1.1.3. Mosaic and regulative eggs:, , organ does not develop in that embryo, Such an egg is called mosaic or determinate e eg. P, Nimertine, Annelids, Molluscs and Ascidians, eens eyeinets
