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Flashcards in Embryology Deck (54):
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During development which part of the gut tube has both dorsal and ventral mesentery?

Foregut

1

How does the pancreas develop within the mesentery?

Tail in dorsal mesentery
Head in ventral mesentery

2

When does lateral folding of the embryo occur during development?

Days 18-24

3

What name is given to the identical ball of cells formed before the blastocyst?

Morula

4

What are the 2 cell layers in a blastocyst?

Trophoblast and Embryoblast

5

When does implantation occur?

Day 6

6

When does the amniotic cavity form?

Day 8

7

What is the Syncitiotrophoblast?

Multinucleated cell, multiple cells fused together, surrounds embryo
Secretes enzymes to aid invasion of the endometrium by the forming embryo

8

When does the primary yolk sac form?

Day 9

9

What does the extraembryonic mesoderm consist of?

Cells, extracellular matrix, cavities (coelom)

10

What is formed by cavitation of extraembryonic mesoderm?

Chorionic cavity, fluid filled

11

At day 13, what structure is present which will form the future umbilicus?

Connecting stalk, made from extraembryonic mesoderm

12

At day 13, what cell laters form the bilayer disc?

Epiblast and hypoblast

13

When is the first time to notice that the menstrual period is late?

Day 15

14

What are the primitive streak and node?

Raised areas of ectoderm, significant cell division
Streak extends from cloaca to primitive node

15

What are primitive groove and pit?

Indentations of ectoderm in centre of streak and node

16

At day 15, what primitive forms of the mouth and anus are present?

Prochordal plate - mouth
Cloacal membrane - anus

17

What is Gastrulation?

Formation of 3 germ cell layers
Migration of epiblast cells from primitive streak towards hypoblast

18

During Gastrulation, which parts of the embryonic disc remain mesoderm free?

Buccopharyngeal and cloacal membranes

19

What does ectoderm develop into?

Skin and neural tissue

20

What does endoderm develop into?

Lining of gut tube, respiratory system and urinary system

21

What does mesoderm develop into?

Paraxial - somite (skeleton, muscle, dermis of skin)
Intermediate - genitourinary
Lateral plate - serous membranes
Muscle, bone, connective tissue, organs, body cavity linings (peritoneum)

22

What are somites?

Somites form axial skeleton, associated muscle & dermis of skin Appear sequentially between days 20 – 30
30-35 pairs formed by paraxial mesoderm
Each supplied by single spinal nerve and migrate to form parts of body
Explains dermatomal sensory mapping of the skin - migrate towards the anterior midline and pull spinal nerves with them

23

Which cavity is drawn around the disc during folding?

Amniotic cavity

24

What is reversal?

Longitudinal folding moves heart, brain, mouth & anus to adult position

25

At what point are tissues of the folding disc folded and reflected?

Umbilicus

26

What forms the dilated terminal portion of the gut tube?

Bladder

27

What does the urorectal septum separate?

Cloaca is separated into the bladder and rectum

28

What is the name of the point where the cloacal membrane meets the septum?

Perineal body

29

What process results in the gut tube having its adult disposition?

Herniation and rotation of the gut tube 270 degrees about the SMA

30

What is an Omphalocele?

Abdominal wall defect
Organs in sac outside abdomen

31

What is gastrocshisis?

Abdominal wall defect
Organs can protrude through umbilicus

32

What can happen if the gut rotates clockwise about the SMA?

Volvulus/obstruction as transverse colon is behind midgut and rotated on own mesentery which can cut off blood supply

33

What is a Meckels Diverticulum?

Remnant of vitellointestinal duct
If infected or inflamed, will present in similar way to appendicitis

34

What is an imperforate anus?

Abnormal urorectal septum formation

35

What developmental feature forms the neck and lower face?

Pharyngeal arches

36

What are pharyngeal arches innervated by?

Each arch is innervated by a cranial nerve and receives blood from an aortic arch artery

37

What features are formed by the pharyngeal arches?

Outer & middle ear
Tongue
Facial & neck muscle
Larynx
Thyroid, parathyroid & thymus gland
Part of facial skeleton

38

Notocord forms within the mesoderm layer but what does it form?

Part of vertebral column

39

What can form from remnants of primitive streak tissue?

Sacrococcygeal teratoma

40

What folds to form the neural tube?

Neural plate

41

What is spina bifida?

Defective neural tube closure together with anomalies of covering tissues, non fusion of vertebral arch

42

What are the 4 types of spina bifida?

Spina bifida occulta - unfused vertebral arch
Meningocoele - dura mater and subarachnoid space protrude through
Meningomyelocoele - spinal cord protrudes through
Myeloschisis - neural tissue fails to migrate so remains at surface

43

What are migrating neural crest cells involved in?

Heart septation
Face & skull connective tissues
GI tract ganglia (Parasympathetic)
Adrenal medulla
Melanocytes
Meninges (Arachnoid & pia)
Dorsal root ganglia
Autonomic nerve ganglia

44

What key events occur during week 1?

Fertilisation
Blastocyst formation
Implantation

45

What key events occur during week 2?

Implantation
Bi laminar disc formation
Amniotic and yolk sac formation

46

What key events occur during week 3?

First missed period
Primitive streak formation
Gastrulation
Neural plate & groove formation & folding
Somite formation

47

What key events occur during week 4?

Heart formation (beats)
Eye and ear primordia
Pharyngeal arches
Neural tube formed & folds fused
Upper limb growth begins

48

What key events occur during week 5?

Further eye development
Feet and hand plates present
Face begins to form
Brain vesicles form
Lower limb growth begins

49

What key events occur during week 6?

Oral & nasal cavities, & upper lip form
External acoustic meatus forms
Digits begin to appear
Gut rotation & return to abdo cavity

50

What key events occur during week 7?

Genital development starts
External ear forms
Palate formation
Gut rotation & return to abdo cavity

51

What is contained in the falciform ligament?

Ligamentum teres - remnant of umbilical vein

52

What is contained in the ventral mesentery?

Liver
Gallbladder
Pancreas

53

What is contained in the dorsal mesentery?

Spleen
Pancreas