DA1 Flashcards
Developmental Anatomy studies….
the development of complex, multicellular organisms
Development: ontogenetic
transformation of zygote into a new individual
Development: phylogenetic
transformation of simple to complex organisms
Challenges to development education:
-limited time -competition for “more important” courses -difficult subject matter for educators and unexposed students
Developmental stages: Embryo
-from time of fertilization to completion of organogenesis -most critical stage!!!!!
Developmental stages: organogenesis
the establishment of major organ primordia
Developmental stages: fetus
reminder of prenatal development devoted to growth, differentiation and maturation of body systems
Which domestic mammal has the longest gestation period?
Horse
What are the three stages of early development?
- Gametogenesis 2. Cleavage 3. Gastrulation
Gametogenesis
First phase of early development Differentiation and maturation of primordial germ cells into gametes
Origin of germ cells
Endoderm of the yolk sac
Oogenesis
Maturation of primordial germ cells into female gametes
- Oogonia differentiate into primary oocytes
- Primary oocytes enter meiosis I and remain in “resting” stage until sexual maturity
- (many oogonia and primary oocytes undergo apoptosis)
- At birth, only “resting” primary oocytes are found in the ovary
- Ovulatory hormones stimulate completion of meiosis I resulting in a haploid secondary oocyte and a polar body
- Ovulated secondary oocyte enters meiosis II, and completion of meiosis II occurs ONLY if fertilization occurs
Oogonia
primordial germ cells within female ebryonic gonad
Once oogonia mature into a female gamete (egg) via meiosis, what happens next?
They continue mitotic divisions in the ovary until birth, then they stop!
Oogenic meiosis is different than spermatogenic meiosis because….
two gametes have special attributes
In the dog and fox, primary oocytes are released at…..
ovulation
Multinucleated ovarian follicles usually….
degenerate
Age-related damage to oocytes
meiotic errors during “resting” stage
Ovulation can either be _____ or _____.
Spontaneous or induced
Meiosis
reduction-division process –> haploid cells
Spermatogenesis
Maturation of primordial germ cells into male gametes
- Spermatogonia continue mitosis then enter “resting” stage of meiosis I until puberty
- At puberty, spermatogonia differentiate into primary spermatocytes
- Meiosis I may be completed at any time resulting in two equal haploid secondary spermatocytes
- Secondary spermatocytes complete meiosis II –> four haploid spermatids
- Spermatids undergo spermiogenesis (maturation) to become motile spermatozoa
Spermatogenesis is a _______ process.
continuous
Capacitation
Physiological changes of spermatozoa in female genital tract necessary for fertilization
Gametogenesis: differential synopsis
Oogenesis vs Spermatogenesis
- Oogenesis: one daughter cell becomes ovum and 3 polar bodies
- Spermatogenesis: each daughter cell develops into a spermatozoon
- Oogenesis: process begins before birth
- Spermatogenesis: process begins at puberty
- Oogenesis: one (several) matures monthly (seasonally)
- Spermatogenesis: millions are produced at a time
Fusion of gametes –> zyogte
Occurs in: ___________
Occurs within the zona pellucida, specifically inside the oocyte.
Steps of fertilization
- Penetration of zona pellucida by spermatozoa
- Fusion of gametes membranes
- Integration of genetic material
Results of fertilization
- Restoration of diploid chormosome number
- sex determination of individual
- Initiation of cleavage
Sex determination in birds, snakes, some insects
The males are homogametic (ZZ) and females are ZY
Sex determiniation in crocodiles, turtles
Determined by incubation temperature of eggs
Second stage of early development: cleavage
Morula
- A spherical mass of cells (blastomeres)formed by rapid mitotic division
- The size of the embryo does not change because zona pellucida is STILL present.
- The zona pellucida prevents adherence and embryo rejection by internal immune system
Second stage of early development: cleavage
Early blastocyst
- Blastula: A single layer of cells lining a central cavity called blastocyst
- Zona pellucida degenerates and implantation follows
- Time and form of implantation differ among species
Second stage of early development: cleavage
Late Blastocyst
- Segregation of blastomeres:
- Trophoblast: outer single-cell layer that forms the fetal membranes
- Inner cell mass: central core of cells that forms the embryo
- At blastocyst stage blastomeres have restricted developmental potneital
Third stage of early development: Gastrulation
- Formation of germ layers:
- Cells if inner cell mass delaminate and form hypoblast surrounding trophoblast
- Hypoblast cells become extraembryonic endoderm (forms yolk sac)
- Remainder of inner cells above hypoblast form epiblast
- Epiblast splits to form:
- Extraembryonic epiblast which lines amniotic cavity
- Embryonic epiblast which is the source of all three germ layers
Derivative of ectoderm
Epidermis and nervous system
Derivatives of mesoderm
- Cardiovascular system
- urinary and genital systems/blood cells
- most of connective and muscular tissue
Derivatives of endoderm
- Digestive and respiratory tracts
- Urinary bladder, tympanic cavity
- Parenchyma of thyroid and parathyroid glands
