Embryology Flashcards Preview

Block 1 lectures > Embryology > Flashcards

Flashcards in Embryology Deck (41):
1

Endoderm derivatives

Epithelial lining of:

GI tract, trachea, bronchi, lungs, liver, urinary bladder

Other:

thyroid, parathyroid, thymus

2

Mesoderm derivatives


Muscles

Bone

Dermis

Connective tissue

Kidneys

Spleen

Cardiovascular structures

Blood

Gonads

 

3

Ectoderm derivatives


Surface ectoderm: epidermis, sailvary glands, sweat glands, mammary glands

Neuroectoderm: CNS, retina

Neural Crest: ANS, dorsal root ganglia, cranial nerves, melanocytes, Schwann cells, adrenal medulla, bones of skull (pharyngeal arches)

4


Organizing center


Instructs differentiation of cells

Ex: Primitive Node (anterior of primitive streak in humans, controls gastrulation; equivalent to Spemann's organizing center in other animals), Isthmus Organizer (in midbrain-hindbrain isthmus; required for cerebellum development)

5


Fertilization sequence of events

Secondary oocyte (in metaphase II) released from ovary -->sperm digest corona radiata --> one sperm penetrates zona pellucida --> block to polyspermy --> secondary oocyte completes meiosis II to make fertilized ovum and second polar body --> egg and sperm undergo rapid DNA synthesis --> nuclear membranes dissolve --> first mitosis

6


Blastocyst


Created when fluid enters morula

Trophoblast: Outer sphere of cells

Embryoblast/Inner Cell Mass: cluster of cells on one inside edge of trophoblast

7

Embryoblast/Inner Cell Mass


Gives rise to entire embryo

Epiblast: surrounds amniotic cavity; gives rise to entire body; (columnar cells); where primitive streak forms and gastrulation eventually occurs

Hypoblast: upper surrounding of exocoelomic cavity/primitive yolk sac (cuboidal cells)

8


Trophoblast

Cytotrophobalst: cells divide and go outward to syncitiotrophoblast and fuse/lose cell membranes

Syncitiotrophoblast: no cell boundaries; secretes HCG; forms lacunae

9


How does the embryo hijack the mother's physiology?


Trophoblast secretes HCG to sustain the corpus luteum which secretes progesterone to sustain endometrium

After about 8 weeks, the placenta takes over progesterone production

10


Placenta previa


An ectopic pregnancy where blastocyst implants too close to cervix and hemorrhaging occurs around 7 months (however can still have viable fetus)

11


3 ways twinning can occur


1) Split at 2 cell stage: 2 amniotic cavities, 2 chorionic cavities, 2 placentas (RARELY happens)

2) Split at early blastocyst: 2 amniotic cavities, 1 chorionic cavity and 1 placenta

3) Split at late blastocyst: 1 amniotic cavity, 1 chorionic cavity, 1 placenta

12


Sirenomelia


Cells moving into primitive streak lose steam at the end and fail to gastrulate properly, giving fused limbs (mermaid limbs)

13


Sacrococcygeal teratoma


Caused by primitive streak persistence; tumor has bits of every germ layer; most common in female fetuses

14

When are embryos most vulnerable to insult?

3-8 weeks

This is when body plan/organ systems are formed

15

Axial mesoderm


Notochord

16


Paraxial mesoderm


Somites create sclerotome (bone and cartilage of vertebral column), myotome (skeletal muscles), dermatome (dermis)

17


Intermediate mesoderm


Kidney

18


Lateral plate mesoderm

Creates mesothelial/serous membranes (peritoneum, pericardium, lung pleura); splits into two divisions and coelomic cavity forms in between them

Parietal/Somatic mesoderm: body wall

Visceral/Splachnic mesoderm: surrounds endodermal organs

19


Extraembryonic mesoderm


Anybody know what this turns into?

20


How does the neural plate begin to form?


Notochord induces it to

21

Forebrain

(Procephalon)


Telencephalon: oflactory nerve

Diencephalon: optic nerve

22

Midbrain

(Mesencephalon)

Cranial nerve III (occulomotor)

23

Hindbrain

(Rhombencephalon)


8 Rhombomeres

Cranial nerves IV to XII

24


Foregut

Epithelium of...

Pharyngeal pouch derivatives: thyroid, parathyroid, thymus, tonsils

Esophagus

Trachea

Lung buds

Stomach

Liver

Gall bladder

Pancreas

Duodenum

25


Midgut


Epithelium of...

Posterior duodenum

Small intestine

Transverse colon (part of it)

26


Hindgut


Epithelium of...

Colon

Rectum

Urinary bladder

Prostate

Urethra

27

Examples of epithelial-mesenchymal transition


1) Gastrulation at primitive streak

2) Neural crest migration

3) Lateral plate forming mesothelium lining of peritoneum (mesenchymal TO epithelial...opposite!)

4) Note: also happens in cancer invasion when cells detach from each other and attach to basement membrane

28

When does basic organogenesis of the fetus complete?

End of 1st trimester

Most sensitive to teratogens during 1st trimester

29

Fetus' genetalia differentiated

14 weeks

30

When does surfactant secretion begin and why is that relevant?

24 weeks

Note: at ~26 weeks (beginning of 3rd trimester) CNS matured enough to support rhythmic breathing so after this point, viable fetus can be born

31

Morphogen gradient responsible for dorsal-ventral axis

BMP

High on ventral side (induces epidermis and lateral plate--most ventral)

(BMP signals through protein kinase receptor that activates Smad TFs)

32

Genes responsible for anterior-posterior axis

Hox genes

33

How do chordin and noggin act?

BMP antagonists that bind BMP and stop it from signaling

Act on dorsal side to inhibit BMP

 

34

Hox gene vs. Homeodomain vs. Homeobox

Hox: gene

Homeodomain: structural motif in the protein that can bind to DNA

Homeobox: DNA that encodes the homeodomain

35

How does retinoic acid affect Hox gene transcription?

RA activates Hox gene transcription by binding receptor and translocating into nucleus

RA sequentially activates Hox gene expression: anterior to posterior

36

Retinoic acid teratogenesis

Hox genes not usually expressed in most anterior pharyngeal arch (containing rhombomeres 1 and 2) but excess RA causes Hox expression there

Causes cleft palate, micrognathia, etc

37


RU 486


Progesterone receptor antagonist

Used in first months of pregnancy, but not after because at that point placenta is making progesterone, and can't block that

38


Malformation


Results from abnormal formation of a structure (usually during embryogenesis)

39

Deformation


Results from impact of mechanical forces on normally-formed structure (usually during fetal period)

40


Disruption


Results from destruction of previously normally formed structure

41


Dysplasia


Results when normal structures are made out of abnormal tissues