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31 Cards in this Set
- Front
- Back
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Gametogenesis |
Process by which the mature germ cells are formed Gametes - Ovum and spermatazoa |
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4 phases of Gametogenesis |
1. Origin and Migration 2. Mitosis 3. Meiosis 4. Structural & Functional Maturation Female/ Male differences in Meiosis |
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When does Gametogenesis begin? With what? |
Week 4 Cell Migration and division of primordial germ cellls |
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Primordial Germ Cells |
Pluripotent - give rise to anything except membranes Origin: Ventro-caudal border of yolk sac Migration: Cells divide during Migration, Cell's migrate to the genital ridge ( Developing Gonads) in the dorsal mesentry Once PCG's are invested by support cell's Gametogenesis begins |
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Mitosis |
Each Daughter cell receives complete set of chromosomes |
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Mitosis in Females |
Oogania - Mitotically active female germ cell - btwn embryonic months 2-5 From few thousand to 7 million cells per ovary Atresia- Reduction of Numbers from the 5th month to 250,000 @ Puberty To 0 @ Menopause |
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Mitosis in Males |
Spermatogonia Mitotically active male germ cell Retains mitotic capacity throughout life |
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Meiosis |
Reduction in chromosomal number from diploid to haploid - half the genetic material Redistribution of maternal and paternal cells in daughter cells Reorganisation of genetic material through crossing over Male = 4 spermatids/ primary spermatocyte Female = 1 definitive oocyte/ primary oocyte |
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Meiosis in Males |
4 spermatids per primary spermatocyte |
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Meiosis in Females |
1 definitive oocyte per primary oocyte 3 polar bodies |
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Structural Maturation Females |
Folliculogenesis At birth - Primary Follicle At each menstrual cycle 5-12 follicles undergo maturation - usually 1 dominant follicle/ cycle Formation of: - Zona Pellucida - Follicular Antrum - Definitive Oocyte or Ovum - Follicular cells, - Carona Radiata |
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Gametogenesis Anomolies - Germ Cell Tumours |
Germ Cell Tumours - Anomolies in the migration of primordial germ cells -> tumours - Usully detected before 3 y/o or after 12 y/o - Intraabdomjnal usually - Classified according to the degree of Differentiation reached before forming a tumour Germinoma - Testes and Ovary Extra-embryonic tumour: Umbilical Vesicle, Choriocarcinoma (Placenta) Embryonic Tumour: Embryonal carcinoma, teratoma |
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Structural Maturation - Males |
Spermiogenesis - Final structural changes in spermatids Head formation - Nucleus Compaction & Acrosome (contains digestive enzymes) Mitochondrial sheath Flagella or Tail Spermatozoa |
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Gametogenesis Anomolies |
Teratomas Germ cell tumour |
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Gametogenesis Anomolies - Teratomas |
Tumour present @ Birth Tumours with tissue representing derivatives from at least one definitive germ layer Sacro-coccygeal teratoma most common Can present later in life in other areas 4 x more frequent in Females |
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Which examples of Trisomy are embryologically viable? |
Trisomy 13, 18, 21 All others are embryologically dull Risk increases with age |
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When does Gametogenesis go wrong? |
Primary Follicle containing more than one oocyte Multinucleated/ and cleated oocyte Spermatazoa w/ visible Anomolies ~10% Chromosomal abnormalities Deletions/ Microdeletions/ imprinting - Cri-du-chat syndrome 5p deletion Cat cry, intellectual disability, Facial features - Angelman - maternal 15q - q13 Prayer Willi - Paternal Gene Mutation |
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Oogenesis |
Production/ Development of the Ovum |
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Oocyte |
A cell in an ovary that undergoes meiosis to form an ovum |
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Polar Body |
A polar body is a small haploid cell that is formed simultaneously as an egg cell during oogenesis, but generally does not have the ability to be fertilized |
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Ovarian Follicle |
Secretes hormones that influence stages of the menstrual cycle |
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Follicular Antrum What does its presence signify |
Portion of the ovarian follicle filled with follicular fluid It has reached the next stage of maturation - Primary -> Secondary follicle |
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Corona Radiata |
Adjacent to Zona Pellucida Supplies vital proteins to the cell |
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Zona Pellucida |
Regulates interactions between ovulated eggs and free sperm during and after fertilisation Supports communication between oocyte and follicular Cell's in oogenesis Protects oocyte, eggs and embryos |
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Spermatogenesis |
Primordial germ cells -> Haploid Spermatazoa |
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Spermatocyte |
Function: divide and produce spermatids Developed from spermatagonia (immature germ cells) |
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Spermatid |
Haploid male gamete Formed from secondary spermicyte (meiosis) |
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Spermatazoa |
Mature Motive make gamete |
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Spermiogenesis |
Final stage of spermatogenesis - Spermatid -> Spermatazoa Shape: Circular-> Flagella, mitochondrial sheath, Head formation( Compact Nucleus, Acrosome - Allows penitration of egg) |
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Acrosome |
Contains digestive enzymes - break down Zona Pellucida, allowing fertilisation Found @ anterior head of spermatozoa |
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Male Gamete Pathway Spermatogenesis |
Primordial Germ Cell Spermatogonia Primary spermatocyte Secondary Spermatocyte Spermatids Spermiogenesis-> Spermatazoa |
