Exam 2 - Lecture 26 (Intro to Embryology) Flashcards
What are congenital defects?
Defects that are present at birth (may not know about it right away or ever)
What are two types of congenital defects?
- Genetic
2. Environmental (drugs, plants, infections, pesticides, radiation, etc.)
What environmental factor plays a big role in veterinary congenital defects?
Drugs (vax, orals, topicals, etc.)
What environmental factor plays a big role in congenital defects in herbivores?
Plants
What is multifactorial inheritance?
A couple of different factors come together to cause birth defects
What are birth defects usually a combo of?
Genetic and environmental causes
What is the highest % of causes of birth defects in vet med?
Unknown
What is a critical period?
Point in time when an organ/organ system is developing, cells are undergoing replication, fetus is MOST exposed to outside influences
What are the two things that are a part of the first critical period of development in the cat?
brain and spinal cord
What critical period extends into postnatal time in the cat?
Development of cerebellum and cerebrum
What happens if an ewe eats Veratrum californicum at day 14-15 of gestation?
Cycloptic/monkey-faced lamb
What plant results in a cycloptic/monkey-faced lamb if the ewe ingests it/what day of gestation?
Veratrum californicum @ day 14-15
What is cerebellar hypoplasia?
Small or underdeveloped cerebellum
What are the 3 general causes for cerebellar hypoplasia?
genetic, infectious, and toxic
What are 2 infectious causes for cerebellar hypoplasia?
- Bovine Viral Diarrhea (BVD)
2. Feline panleukopenia
When is the calf affected in BVD?
100-170 days of gestation
When is the kitten affected in feline panleukopenia?
Last part of gestation (9-14d) to early postnatal period (9-14d postnatally) (has to be infected during critical period)
What can totipotent cells give rise to?
Entire, complete organism
As stem cells differentiate, there is increased _____ on what the cell can become.
Restriction
What is the zona pellucida?
Outer layer surrounding the ovum during the first cell cleavage division
What are blastomeres?
Early daughter cells that divide
How many blastomeres are present in the second cleavage division?
4
What is a morula?
Mulberry shaped phase of cell cleavage that consists of outer and inner blastomeres.
What is a blastula and what are its components?
Phase of cell cleavage where the outer layer is trophoblasts, inner blastomeres are present just inside the trophoblasts, and the cavity is the blastocoele.
What is the role of the blastocoele?
To aid in diffusion
When the zona pellucida is in place, the cell number _____ but their size _____.
increases; decreases
What is the fate of outer blastomeres in the morula?
Form placenta/trophoblasts
What is the fate of inner blastomeres in the morula?
They are not restricted; contribute to inner cell mass (embryo) of the blastula
What does gastrulation give rise to?
The 3 germ layers
Gastrulation marks the beginning of _____.
Organ and body development
When does gatrulation occur?
14d into gestation
What are the 2 cavities of the developing embryo?
- Embryonic cavity
2. Yolk sac
The embryo is a _____ disc.
bilaminar
What are the two layers of the bilaminar disc?
Epiblast cells (tall) and hypoblast cells (shorter, underneath epi)
What 2 things form at the beginning of gastrulation and where?
- Primitive streak
- Primitive node
Form in the amniotic cavity
What 4 things can you tell from the primitive streak and node?
R/L, Cranial/Caudal (head/tail)
Epiblast cells flow through the _____ to give rise to the 3 germ layers.
primitive groove
Epiblast cells that flow deep through the primitive groove give rise to _____.
Endoderm
Epiblast cells that flow through the primitive groove to an intermediate location give rise to _____.
Mesoderm
Epiblast cells that don’t migrate through the primitive groove give rise to _____.
Ectoderm
At the notochord, epiblast cells flow through the _____.
primitive node
Epiblast cells that flow through the primitive node flow in a _____ direction and lie between _____ and _____.
cranial; ectoderm; endoderm
What 3 things does ectoderm give rise to?
- Epidermis
- Neural tissue
- Skeletal/c.t. of the head
What 2 things does endoderm give rise to?
- Lining of the digestive and respiratory tracts
2. Organs of digestion
What 4 things does mesoderm give rise to?
- Muscle
- Skeletal tissue
- Urogenital
- Cardiovascular
What develops within the mesoderm to kick off the start of body formation/coelom closure?
tiny cavities/coelomic vesicles
What do the coelomic vesicles form when they combine?
coelom
What 2 things form along with the formation of the coelom?
Splanchnic and somatic mesoderm
What does splanchnic mesoderm eventually give rise to?
internal organs
What does somatic mesoderm eventually give rise to?
body wall
Which way do splanchnic and somatic mesoderms grow and what do they form?
ventrally and medially; form gut tube and closure of embryo
What is schistosomus reflexus and what happens as a result?
Condition where somatic mesoderm never made contact ventrally; head and legs are at one end of the body while viscera is at the other end.
