Cleavage and Blastulation - Students' Copy - Developmental Anatomy PDF
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Dr. Krysta Riza Jacalan Pontillas
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Summary
This document is a student's copy of lab notes for a developmental anatomy course. The notes cover the stages of early embryonic development, including cleavage and blastulation, along with the various types of cleavage. The notes also discuss twinning and look into different varieties of twins.
Full Transcript
VAN 53 A DEVELOPMENTAL ANATOMY LABORATORY CLEAVAGE & BLASTULATION EXERCISE 3 Dr. Krysta Riza Jacalan Pontillas EARLY EMBRYONIC DEVELOPMENTAL STAGES 1. Gametogenesis 2. Fertilization 3. Cleavage & Blastulation 4. Gastrulation 5. Neurulation 6....
VAN 53 A DEVELOPMENTAL ANATOMY LABORATORY CLEAVAGE & BLASTULATION EXERCISE 3 Dr. Krysta Riza Jacalan Pontillas EARLY EMBRYONIC DEVELOPMENTAL STAGES 1. Gametogenesis 2. Fertilization 3. Cleavage & Blastulation 4. Gastrulation 5. Neurulation 6. Organogenesis EARLY EMBRYONIC DEVELOPMENTAL STAGES 1. Gametogenesis 2. Fertilization 3. Cleavage & Blastulation 4. Gastrulation 5. Neurulation 6. Organogenesis 15 - 30 mins 1 hour 2-3 hours 20 hours Cleavage - series of mitotic divisions whereby the enormous volume of egg cytoplasm is divided into numerous smaller, nucleated cells. Cleavage - series of mitotic divisions whereby the enormous volume of egg cytoplasm is divided into numerous smaller, nucleated cells. TYPES OF CLEAVAGE https://rb.gy/zcdhkg Morula - solid mass of blastomeres resulting from a number of cleavages of a zygote, or fertilized egg. Blastula - -A hollow sphere of cells, or blastomeres, produced during the development of an embryo by repeated cleavage of a fertilized egg. The cells of the blastula form an epithelial (covering) layer, called the blastoderm, enclosing a fluid-filled cavity, the blastocoel. Blastodisc - single female cell Blastoderm - fertilized Few hours after fertilization. EARLY EMBRYONIC DEVELOPMENTAL STAGES 1. Gametogenesis 2. Fertilization 3. Cleavage & Blastulation 4. Gastrulation 5. Neurulation 6. Organogenesis EMBRYONIC DUPLICATION OR TWINNING Twinning - development of 2 or more embryos in a dam that normally gives birth to 1 offspring per gestation Causes: 1. fertilization of separate ova 2. complete/partial separation of blastomeres and blastocyst during cleavage 3. duplication after gastrula stage (in organ-forming regions) 4. one blood supply shared by completely separated twins TYPES OF TWINS 1. Free symmetrical monozygotic twins identical twins one zygote same sex same genetic composition zygote duplicates itself TYPES OF TWINS 2. Conjoined (fused) symmetrical twins incomplete separation of blastomeres later in embryonic development zygote incompletely divides Monster = abnormal twins wherein head or appendages are duplicated Dicephalus = 2 heads Diprosopus = 2 faces in one head Dicaudatus = 2 tails Tetrabrachius = 4 thoracic limbs Tetrascelus = 4 pelvic limbs TYPES OF TWINS 3. Free Asymmetrical twins monozygotic or dizygotic twins separate twins: one normal, one rudimentary abnormal twin survives by being attached to blood supply of fetal membranes of normal twin abnormal twin = amorphous globosus, anidian (formless) fetus, acardiac fetus or holocardius no body formed TYPES OF TWINS 4. Conjoined asymmetrical twins occur after gastrulation when specific fields are becoming organized unequal size (heteropagus) one normal individuaal = autosite extra body part attached to it = parasite parasite survives by attaching to blood supply of autosite TYPES OF TWINS 5. Free symmetrical dizygotic (or polyzygotic) twins fraternal twins 2 or more zygotes develop separately and independently separate fetal membranes and placenta during same pregnancy same sex or different sexes TYPES OF TWINS Freemartinism - genetic female born as a twin to a male sterile female freemartin heifer
