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Year Two Revision Super-Deck > Embryology > Flashcards

Flashcards in Embryology Deck (82):
1

What structures comprise the alimentary canal?

Mouth to anus, the whole gut tube including all associated glands and organs

2

At what week of development does the gut tube form?

Forth week

3

What membranes encore the primordial gut at both its cranial and caudal end?

Cranial - Oropharyngeal membrane
Caudal - Cloacal membrane

4

What is the process of gastrulation?

Formation of the trilaminar disc (echo, meso and endoderm)

5

What three regions is the primordial gut tube divided into?

Foregut, midgut and hindgut

6

What does the endoderm of the primordial gut form?

Most of the gut including the epithelium and glandular tissue

7

Epithelium from the cranial and caudal end of the gut are derived from what two gut structures? Give specific names.

Ectoderm (stomodeum) and anal pit (proctoderm)

8

What forms the embryonic cavity at the forth week of development?

Intraembryonic coelom

9

The embryonic body cavity divides into what three well defined structures?

Peritoneal and pericardial cavities plus two pericardia-peritoneal canals

10

What are the structures derived from the foregut?

Remember pneumonic: PLODL

P - primordial larynx
L - lower res. tract
O - oesophagus and stomach
D - duodenum
L - liver and biliary apparatus (including the pancreas)

11

What are the structures derived from the foregut?

P - primordial larynx
L - lower res. tract
O - oesophagus and stomach
D - duodenum
L - liver and biliary apparatus (including the pancreas)

12

What is the pharynx?

Space in the throat which is shared by both the digestive and respiratory systems

13

What is the duodenum?

Proximal tubing of intestines, distal to the stomach, site of secretion of biliary apparatus

14

What is oesophageal atresia?

Congenital non-separation/blockage/extensive narrowing of oesophagus

15

What is abnormal deviation of the tracheo-oesophageal septum called?

Oesophageal fistula

16

What is polyhydraminos?

Too much amniotic fluid around the foetus; usually due to atresia preventing adequate drainage

17

Outline the main events of stomach development

1. Rotation of stomach 90 degrees clockwise
2. Mesenteries of stomach and omental bursa develop

18

What is hypertrophic pyloric stenosis?

Overgrowth of the pyloric sphincter (opening from stomach into the duodenum)

19

Outline the development of the liver and biliary apparatus

Hepatic diverticulum septates

20

List possible anomalies of the hepatic system arising from the embryo

Accessory ducts (occurs in 5% of the population) and extrahepatic biliary atresia (obliteration of the bile ducts)

21

What occurs if the ventral bud of the primordial stomach fails to migrate around the duodenum correctly? What pathology can this cause?

Annular pancreas

Duodenal stenosis

22

Describe the accessory pancreatic tissue

Pancreatic tissues may form in other areas of the foregut

23

Explain the origins and development of the spleen

End of the 4th week of gestation - mesenchymal condensation develops forming the dorsal mesogastrium

During the 5th week of gestation the mesenchyme differentiates into spleen tissue

24

What laminar disc does the spleen arise from?

Mesoderm

25

Outline the main events of the midgut loop

1. Herniation (physiological umbilical herniation)
2. Rotation of midgut 90 degrees anticlockwise in the umbilical cord
3. Retraction of intestinal loops 180 degrees further
4. Fixation of intestines in place

26

In what percentage of people does the small vitelline duct persist?

2-4%

27

What does a persistent vitelline duct form?

Merkel Diverticulum

28

What complications can arise from a persistent vitelline duct?

Fistula or cyst

29

What is omphalocele?

Herniation of the abdominal viscera through an enlarged umbilical ring

30

What viscera may an omphacele include?

Herniation of the liver, stomach and intestinal loops

31

What covers the viscera of an omphacele?

Amnion

32

What is an amnion?

A membrane which closely covers the embryo

33

What is herniation of abdominal contents directly through the body wall and into the amniotic cavity called?

Gastroschisis

34

What is a suggested cause for a rising prevalence of gastroscisis in young women?

Cocaine use

35

What is the prevalence of gastroschisis NOT associated with?

Chromosomal defects

36

What structures comprise the hindgut?

Remember pneumonic: DURSD

D - distal third of transverse colon
U - upper part of anal canal
R - rectum
S - sigmoid colon
D -descending colon

37

What does the endoderm of the hindgut also form which is not part of the gut tube?

The lining of the bladder and urethra

38

What is the cloaca?

The expanded terminal part of the hindgut and endoderm lined chamber - primordial rectum

39

What is allantois?

The ventral diverticular of the cloaca

40

What is the function of the cloacal membrane?

Separates the cloaca and the anal pit

41

Describe the partitioning of the cloaca

1. Week 7 - the cloacal membrane ruptures; opening the hindgut
2. Ectoderm proliferates at the anal canal and closes the caudal end
3. Anal canal re-opens at week 9

42

List some embrological hindgut abnormalities?

Urorectal fistula
Rectovaginal fistula
Rectoanal atresia
Imperforate anus

43

What are pharyngeal/bran arches?

A series or arches which develop around the future mouth (somatodeum) and the pharynx

44

What are the branchial arches for?

1. Support the primitive pharynx
2. Face and neck develops from them

45

Outline the development of the branchial arches

Six begin to develop around week 4 - no. 5 regresses and so the arches remaining are 1, 2, 3, 4 and 6

46

What embryological tissue makes up the branchial arches?

1.Ectoderm lies on the outside (forms clefts between the arches)
2. Mesoderm - forms the cartilage and muscles aspects
3. Endoderm - forms the pouches between arches

47

How are each of the branchial arches innervated?

1st - CNV3
2nd - CN VII
3rd - CN IX
4th - Superior laryngeal branch of CN X
6th - Recurrent branch of CN X

48

What are the fates of the pharyngeal cartilages?

1st (Meckel's Cartilage) - Mandible, incus and malleus
2nd - Stapes, styloid process, styloid ligament, lesser horn of hyoid
3rd - body and greater horn of hyoid
4th - Thyroid cartilage
6th - cricoid cartilage

49

What other structures are formed from the pharyngeal arches?

Tongue, thyroid, parathyroid and pituitary gland

50

Outline the development of the face

Develops from five processes/prominences:

- One frontonasal process
- Two maxillary processes
- Two mandibular processes

51

Outline the fate of the mandibular processes

Fuses in the midline

52

Outline the fate of the frontonasal process

Divides into the medial and lateral processes

Medial develops into the philtrum
Lateral develops into the nostrils

53

Outline the three stages of palatine development?

1. Medial nasal process grows down (forming the philtrum)
2. From the maxillary processes, two palatine shelves grow inwards
3. Palatine shelves fuse (forming secondary palate)

54

What abnormalities may arise from the development of the palate?

Cleft palate

55

What officiation process occurs in the development of the cranial vault?

Membranous (no cartilagenous stage)

56

Outline the development of the cranial vault

Mesenchyme drived from mesoderm that lies above the developing brain ossifies

57

What officiation process occurs in the development of the base of the skull?

Endochondral (cartilagenous stage)

58

What is the viscerocranium?

Skeleton of the face

59

Outline the development of the viscerocranium

Partly from branchial arches and partly from sensory capsules (derived from mesoderm of somites)

60

After the formation of the neural fold, what occurs at ay 22 of gestation?

Neural fold forms the neural tube with two holes at either end (neuropores)

61

When does the anterior and posterior neuropore close?

Anterior - approx. 25 days
Posterior - approx. 27 days

62

What group of disorders is caused by failure of the neural tube to close properly?

Neural Tube Defects (NTDs)

63

When does the development of brain vesicles begin?

Begin with the closure of the anterior neuropore

64

What are the three primary brain vesicles?

1. Proencephalon (forebrain)
2. Mesencephalon (Midbrain)
3. Rhombencephalon (Hindbrain)

65

When do the three primary vesicles of the brain from the five secondary vesicles?

At the 5th week of gestation

66

What are the five secondary vesicles?

1. Telencephalon
2. Diencephalon
3. Mesencephalon
4. Metencephalon
5. Myelencephalon

67

In order to fill the cranial space the primordial brain folds to form three flexures ; name them, state when they occur and give their location

1. Cephalic flexure - 3rd week - between mid and hindbrain

2. Cervical flexure - 4th week - between hindbrain and spinal cord

3. Pontine flexure - 5th week - behind metencephalon and myelencephalon

68

What are the derivative structures of the telencephalon

Cerebral hemispheres
Hippocampus
Basal ganglia

69

What are the derivative structures of the diencephalon

Thalamus
Hypothalamus
Pituitary gland
Pineal gland

70

What are the derivative structures of the mesencephalon

Superior and inferior colliculi

71

What are the derivative structures of the rhombencephalon

Mesencephalon = cerebellum and pons
Mylencephalon = medulla

72

What system is formed from the lumen of the neural tube?

Ventricular system

73

When does CSF production begin in the foetus?

5th week

74

Where is CSF produced mainly?

In the choroid plexi of the 3rd and 4th ventricles

75

Where does CSF drain?

Drains into the subarachnoid space in the rood of the 4th ventricle and eventually into the venous system

76

Outline the differentiation of the neural tube; state where they divide

Lays down single layer of pseudostratified neuroepithelium which divide at the ventricular surface

77

What does the neuroepithelium differentiate into ?

All neurones and glia except microglia

78

How are are microglia formed?

From mesenchymal cells which migrate into the CNS

79

How are spinal nerves formed?

Mix of both neural crest cells and neural tube

80

How long does it take for the spinal cord to extend to its fullest length in gestation?

3 months

81

Why does the position of the spinal cord change during growth?

Dura mater and vertebral column grow faster therefore the cord grows to increasingly higher levels (L2 in children to L3 in adults)

82

How are the sympathetic and parasympathetic ganglia formed?

Neural crest cells