Chapter 3: Embryology Flashcards
Define teratogen.
A substance that can cause birth defects or death of the embryo.
ie. alcohol, tobacco smoke, drugs, some viruses, aspirin, etc
Describe the germ layer: Ectoderm.
What body parts are derived from the ectoderm?
Epidermis of skin (including hair, nails, sweat glands, mammary glands) Nervous tissue and sense organs Pituitary gland Adrenal medulla Enamel of teeth Lens of the eye
Describe the germ layer: Mesoderm.
What body parts are derived from the mesoderm?
Dermis of skin Epithelial lining blood vessels, lymph vessels, serous membranes Muscle tissue Connective tissue Adrenal cortex Heart Kidneys and ureters Internal reproductive organs Spleen
Describe the germ layer: Endoderm.
What body parts are derived from the endoderm?
Epithelial lining of respiratory tract, GI tract, urinary tract, reproductive tract, tympanic cavity, auditory tube Lover Gallbladder Pancreas Palatine tonsils Thyroid gland Parathyroid glands Thymus
What is meiosis?
A type of sex cell division that starts with a diploid parent cell and produces 2 haploid daughter cells
What is mitosis?
Cell division process that takes place in the somatic cells (all cells of the body except the sex cells)
Results in 2 cells identical to the parent cell
Define embryology.
The study of the developmental events that occur during the prenatal period.
Define differentiation.
Formation and organization of all the cells in the human body.
Define reproduction.
new individuals are produced from generation to generation.
Define embryogenesis.
The developmental processes that occur in the pre-embryonic and embryonic periods.
Define and describe gametogenesis.
Formation and development of sex cells (gametes).
Gametes (sperm in men; secondary oocytes in women) are each haploid (contain 23 chromosomes).
List the developmental stages and structures in the pre-embryonic period.
First 2 weeks of development; zygote becomes a spherical, multicellular structure; blastocyst implants in the lining of uterus
zygote - 2 cell - 4 cell - morula - blastocyst
Describe fertilization.
Two cells fuse to form a new cell called a zygote which contains genetic material derived from both parents.
Name the 3 primary germ layers.
Diagram - Pg. 73
Ectoderm
Mesoderm
Endoderm
Define the time period of the fetal stage of development.
The last 30 weeks of development.
Define and describe spermatogenesis.
In males. Spermatogonia produce spermatocytes in the testes. They undergo meiosis and become spermatids who then lose much of their cytoplasm and grow a flagellum - becoming a sperm. 4 sperm come from 1 spermatocyte.
22 autosomes and 1 X or Y chromosome
Define and describe oogenesis.
In females. Oocytes are produced by oogonia in the ovaries and they stop development in Prophase 1. Now they are a primary oocyte. When female reaches puberty, each month one becomes a secondary oocyte and is ovulated. The corona radiate and zone pellucid form protective layers around the secondary oocyte.
If not fertilized, it degenerates after 24 hours.
22 autosomes and 1 X chromosome.
List and describe the 3 stages of embryogenesis.
Diagram - Pg. 55
Cleavage: zygote divides by mitosis to form blastocyst. # of cells incases but the whole size stays the same. After 3rd cleavage division cells become tightly compacted ball called a morula
Gastrulation: blastocyst cells form 3 primary germ layers
Organogenesis: the 3 primary germ layers arrange themselves in ways that give rise to all the organs within the body
Amnion
thin layer of cells that forms above and is derived from the epiblast
encloses the entire embryo in a fluid filled sac called the amniotic cavity.
Amniotic membrane secretes fluid that bathes the embryo.
Placenta
Functions in exchange of nutrients, waste, and respiratory gases between the maternal and fetal bloodstreams.
Transmission of antibodies from mom to baby.
Production of hormones to build and maintain the uterine lining.
Outline structures and phases in meiosis.
Diagram - Pg. 57
Starts with diploid cell
Meiosis I produces 2 diploid daughter cells
Meiousis II turns 2 diploid cells into 4 haploid cells
Crossing over only occurs in prophase I
Chorion
outermost membrane covering the fetus
cells blend with the functional layer of the endometrium and form the placenta.
Gastrulation
3rd week of development.
Critical period in the development of the embryo
Formation of the 3 primary germ layers occurs:
Ectoderm, Mesoderm, Endoderm.
Organogenesis
once 3 primary germ layers have formed, this can begin. Organ systems can develop and the shape of the limbs takes place.
