Embryology Flashcards

1
Q

How does the pancreas develop within the mesentery?

A

Tail in dorsal mesentery

Head in ventral mesentery

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2
Q

When does lateral folding of the embryo occur during development?

A

Days 18-24

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3
Q

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

A

Morula

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4
Q

What are the 2 cell layers in a blastocyst?

A

Trophoblast and Embryoblast

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5
Q

When does implantation occur?

A

Day 6

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6
Q

When does the amniotic cavity form?

A

Day 8

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7
Q

What is the Syncitiotrophoblast?

A

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

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8
Q

When does the primary yolk sac form?

A

Day 9

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9
Q

What does the extraembryonic mesoderm consist of?

A

Cells, extracellular matrix, cavities (coelom)

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10
Q

What is formed by cavitation of extraembryonic mesoderm?

A

Chorionic cavity, fluid filled

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11
Q

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

A

Connecting stalk, made from extraembryonic mesoderm

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12
Q

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

A

Epiblast and hypoblast

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13
Q

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

A

Day 15

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14
Q

What are the primitive streak and node?

A

Raised areas of ectoderm, significant cell division

Streak extends from cloaca to primitive node

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15
Q

What are primitive groove and pit?

A

Indentations of ectoderm in centre of streak and node

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16
Q

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

A

Prochordal plate - mouth

Cloacal membrane - anus

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17
Q

What is Gastrulation?

A

Formation of 3 germ cell layers

Migration of epiblast cells from primitive streak towards hypoblast

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18
Q

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

A

Buccopharyngeal and cloacal membranes

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19
Q

What does ectoderm develop into?

A

Skin and neural tissue

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20
Q

What does endoderm develop into?

A

Lining of gut tube, respiratory system and urinary system

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21
Q

What does mesoderm develop into?

A

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

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22
Q

What are somites?

A

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
Q

Which cavity is drawn around the disc during folding?

A

Amniotic cavity

24
Q

What is reversal?

A

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

25
Q

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

A

Umbilicus

26
Q

What forms the dilated terminal portion of the gut tube?

A

Bladder

27
Q

What does the urorectal septum separate?

A

Cloaca is separated into the bladder and rectum

28
Q

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

A

Perineal body

29
Q

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

A

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

30
Q

What is an Omphalocele?

A

Abdominal wall defect

Organs in sac outside abdomen

31
Q

What is gastrocshisis?

A

Abdominal wall defect

Organs can protrude through umbilicus

32
Q

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

A

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

33
Q

What is a Meckels Diverticulum?

A

Remnant of vitellointestinal duct

If infected or inflamed, will present in similar way to appendicitis

34
Q

What is an imperforate anus?

A

Abnormal urorectal septum formation

35
Q

What developmental feature forms the neck and lower face?

A

Pharyngeal arches

36
Q

What are pharyngeal arches innervated by?

A

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

37
Q

What features are formed by the pharyngeal arches?

A
Outer & middle ear 
Tongue 
Facial & neck muscle 
Larynx 
Thyroid, parathyroid & thymus gland 
Part of facial skeleton
38
Q

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

A

Part of vertebral column

39
Q

What can form from remnants of primitive streak tissue?

A

Sacrococcygeal teratoma

40
Q

What folds to form the neural tube?

A

Neural plate

41
Q

What is spina bifida?

A

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

42
Q

What are the 4 types of spina bifida?

A

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
Q

What are migrating neural crest cells involved in?

A
Heart septation 
Face & skull connective tissues 
GI tract ganglia (Parasympathetic) 
Adrenal medulla 
Melanocytes 
Meninges (Arachnoid & pia) 
Dorsal root ganglia 
Autonomic nerve ganglia
44
Q

What key events occur during week 1?

A

Fertilisation
Blastocyst formation
Implantation

45
Q

What key events occur during week 2?

A

Implantation
Bi laminar disc formation
Amniotic and yolk sac formation

46
Q

What key events occur during week 3?

A
First missed period
Primitive streak formation
Gastrulation
Neural plate & groove formation & folding
Somite formation
47
Q

What key events occur during week 4?

A
Heart formation (beats) 
Eye and ear primordia 
Pharyngeal arches 
Neural tube formed & folds fused
Upper limb growth begins
48
Q

What key events occur during week 5?

A
Further eye development 
Feet and hand plates present
Face begins to form 
Brain vesicles form 
Lower limb growth begins
49
Q

What key events occur during week 6?

A

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

50
Q

What key events occur during week 7?

A

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

51
Q

What is contained in the falciform ligament?

A

Ligamentum teres - remnant of umbilical vein

52
Q

What is contained in the ventral mesentery?

A

Liver
Gallbladder
Pancreas

53
Q

What is contained in the dorsal mesentery?

A

Spleen

Pancreas

54
Q

During development which part of the gut tube has both dorsal and ventral mesentery?

A

Foregut