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Block 1 lectures > Embryology > Flashcards

Embryology Flashcards

1
Q

Endoderm derivatives

A

Epithelial lining of:

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

Other:

thyroid, parathyroid, thymus

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2
Q

Mesoderm derivatives

A

Muscles

Bone

Dermis

Connective tissue

Kidneys

Spleen

Cardiovascular structures

Blood

Gonads

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3
Q

Ectoderm derivatives

A

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)

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4
Q

Organizing center

A

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)

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5
Q

Fertilization sequence of events

A

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

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6
Q

Blastocyst

A

Created when fluid enters morula

Trophoblast: Outer sphere of cells

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

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7
Q

Embryoblast/Inner Cell Mass

A

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)

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8
Q

Trophoblast

A

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

Syncitiotrophoblast: no cell boundaries; secretes HCG; forms lacunae

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9
Q

How does the embryo hijack the mother’s physiology?

A

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

After about 8 weeks, the placenta takes over progesterone production

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10
Q

Placenta previa

A

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

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11
Q

3 ways twinning can occur

A

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

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12
Q

Sirenomelia

A

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

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13
Q

Sacrococcygeal teratoma

A

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

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14
Q

When are embryos most vulnerable to insult?

A

3-8 weeks

This is when body plan/organ systems are formed

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15
Q

Axial mesoderm

A

Notochord

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16
Q

Paraxial mesoderm

A

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

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17
Q

Intermediate mesoderm

A

Kidney

18
Q

Lateral plate mesoderm

A

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
Q

Extraembryonic mesoderm

A

Anybody know what this turns into?

20
Q

How does the neural plate begin to form?

A

Notochord induces it to

21
Q

Forebrain

(Procephalon)

A

Telencephalon: oflactory nerve

Diencephalon: optic nerve

22
Q

Midbrain

(Mesencephalon)

A

Cranial nerve III (occulomotor)

23
Q

Hindbrain

(Rhombencephalon)

A

8 Rhombomeres

Cranial nerves IV to XII

24
Q

Foregut

A

Epithelium of…

Pharyngeal pouch derivatives: thyroid, parathyroid, thymus, tonsils

Esophagus

Trachea

Lung buds

Stomach

Liver

Gall bladder

Pancreas

Duodenum

25
Q

Midgut

A

Epithelium of…

Posterior duodenum

Small intestine

Transverse colon (part of it)

26
Q

Hindgut

A

Epithelium of…

Colon

Rectum

Urinary bladder

Prostate

Urethra

27
Q

Examples of epithelial-mesenchymal transition

A

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
Q

When does basic organogenesis of the fetus complete?

A

End of 1st trimester

Most sensitive to teratogens during 1st trimester

29
Q

Fetus’ genetalia differentiated

A

14 weeks

30
Q

When does surfactant secretion begin and why is that relevant?

A

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
Q

Morphogen gradient responsible for dorsal-ventral axis

A

BMP

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

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

32
Q

Genes responsible for anterior-posterior axis

A

Hox genes

33
Q

How do chordin and noggin act?

A

BMP antagonists that bind BMP and stop it from signaling

Act on dorsal side to inhibit BMP

34
Q

Hox gene vs. Homeodomain vs. Homeobox

A

Hox: gene

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

Homeobox: DNA that encodes the homeodomain

35
Q

How does retinoic acid affect Hox gene transcription?

A

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

RA sequentially activates Hox gene expression: anterior to posterior

36
Q

Retinoic acid teratogenesis

A

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
Q

RU 486

A

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
Q

Malformation

A

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

39
Q

Deformation

A

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

40
Q

Disruption

A

Results from destruction of previously normally formed structure

41
Q

Dysplasia

A

Results when normal structures are made out of abnormal tissues

Block 1 lectures (29 decks)

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