Kuehn Flashcards
Zygote
fertilized egg; single cell
Embryo
2-8 weeks
Fetus
9 weeks - birth; starts at 57th day
Conceptus
embryo or fetus + al surrounding membranes
Trimester
1/3 human development time
Meosis
Gamete formation; Two cell divisions Only occurs in germinal cells (gonads) 1 DNA replication, 2 divisions 4N --> 2N --> N
Mitosis
Occurs in all cells
1 DNA replication, 1 division
4N –> 2N
Spermatogenesis
Spertmatogonia undergo mitosis
Primary and secondary spermatocytes undergo meiosis
Spermiogenesis
Morphological differentiation of spermatids
Oogonium
Only in fetus
All oogonia complete differentiation into primary oocytes by birth
Primary oocyte
Found in most follicles
Remains in prophase of division 1 until some signal initiates further development
Ovum
forms only after fusion w/sperm
Follicles
Contains oocyte plus associated supporting cells
Primordial follicle
1 thin layer of follicular cells
Primary follicle
1 cuboidal layer of follicular cells
Secondary follicle
growing follicle
Mature follicle
contains antrum, primary/secondary oocyte
Ovulation
Hormone controlled enzymes reduce the thickness of the ovary wall
Secondary oocyte ruptures the outer epithelium and forces them into the peritoneal cavity
Blastomeres of equal size and surrounded by zone pellucida
2-4 cell stage
Last synchronous division stage
8 cell stage
Ball of 12-32 cells still bound in zone pellucida
morula
Cells in morula shrink and migrate to the edge leaving a cavity in the middle; Outer cells = trophoblast; Inner cells = embryoblast
blastocyst
Mesoderm
Middle of 3 primary germ layers
Develops splanchnopleure and somatopleure
Extra-embryonic mesoderm
develops from yolk sac epithelium
Intra-embryonic mesoderm
develops from epiblast
Epiblast becomes
ectoderm
Hypoblast becomes
endoderm
Notochord
Arises from epiblast at primitive node
Eventually forms solid mass that will eventually disappear
Dermamyotome
Creates all muscles in body
Sclerotome
Creates vertebrae and intervertebral disks
Somatopleure
Rest of skeleton
Sonic Hedge Hog
Expressed by notochord and activates folding cycle
Edge of neural plate form a groove = neural crest
Ectoderm creates
skin, hair, nails, tooth enamel, anterior pituitary
Endoderm creates
thyroid, lungs, trachea, thymus, bladder
Intermediate mesoderm creates
kidney, ureter, gonads
Lateral plate mesoderm somatopleure creates
bones, cartilage, fascia, vasculature
Lateral plate mesoderm splanchnopleure creates
visceral smooth muscle, visceral fascia
Neuroectoderm
brain, brainstem, spinal cord
Neural crest
melanocytes, peripheral nervous system, adrenal medulla, meninges
Which pharyngeal arches (PA) degenerate early?
1 & 2
PA 1 maxillary division derivatives
max division of trigem, mastication mm, maxillary b
PA 1 mandibular division derivatives
mandib division of trigem, mandibular b, meckel’s cartilage
PA 2 derivatives
facial n, facial expression mm, hyoid bone, Reichert’s cartilage
PA 3 derivatives
glossopharyngeal n, stylopharyngeus m
PA4 derivatives
vagus n, cricothyroid and mm of pharynx, thyroid cartilage
PA6 derivatives
vagus n, intrinsic mm of larynx, cricoid cartilage
Mesenchymal migration
4th-5th week
Condensation of mesoderm
5th-6th week
Chondrification
6th week
Primary ossification
7-12 weeks
Secondary ossification
birth-9 years
Fusion of epiphyseal plates
18-25 years
What forms late in the 5th week?
Epimere (deep back muscles)
Hypomere (appendicular and body wall muscles)
Somatopleure (forms bone, cartilage and CT)
Amniotic membrane consists of
Yolk sac membrane, chorionic membrane, allantois, conecting stalk
When is a fetus viable?
3rd trimester
What occurs in a development defect during the 1st two weeks?
embryionic death
What occurs in a development defect during weeks 3-8?
serious malformation
What occurs in a development defect during week 9-birth?
progressively less severe