Embryology Flashcards

1
Q

What is neurulation

A

Process in which the neural tube forms

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2
Q

When does neurulation take place

A

Week 3-4

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3
Q

What will the neural tube later become

A

CNS: Brain, spinal cord, meninges
As well as part of the bones that surround them

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4
Q

What is gastrulation and when does it take place?

A

Week 3
The three primary germ layers (ectoderms, mesoderm, endoderm) form and start becoming different types of tissue

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5
Q

What will the ectoderm differentiate into

A

Nervous system and skin

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6
Q

What will the mesoderm become

A

Connective tissue, bone , muscle, urogenital organs, pleura, peritoneal linings of the body cavity

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7
Q

What will the endoderm eventually become

A

Lining of the internal organs such as GIT and lining of the airways

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8
Q

What structure induces neurulation

A

Notochord

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9
Q

What will the notochord eventually develop into

A

Nucleus pulposus of the intervertebral disc

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10
Q

What does the neural tube come off of

A

Ectoderm

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11
Q

What happens at the end of week 3 related to neurulation

A

The lateral edges of the ectoderm become more elevated and will form the neural fold.
The depressed mid-region is called the neural groove.
The whole thing is referred to as the neural plate

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12
Q

How does neurulation advance

A

Both cranially and caudally
It starts from the mid-region

This means that at the end of neurulation, the cranial end will give rise to the brain
Caudally will be the spinal cord

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13
Q

How is the neural tube formed

A

Fusion of neural folds together
Starts in the middle and goes both cranially and caudally

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14
Q

How is a neural crest formed?

A

During neurulation as the neural tube forms, some of the ectodermal cells from the tube migrate form several layers of cells called the neural crest

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15
Q

What will the neural crest give rise to

A

Structures that work very closely with CNS

This includes the peripheral nervous system spinal and cranial nerves and their ganglia

Autonomic nervous system ganglia

E.g
Schwann cells, Pigment cells, adrenal medulla, bony skull, meninges, dermis
Sensory (dorsal root) ganglia
CN 5,7,9,10

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16
Q

What will the remaining ectoderm after neurulation become

A

Skin

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17
Q

What does the spinal cord of the neural tube become

A

Spine

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18
Q

What does the rhombencephalon of the neural tube become

A

Pons
Cerebellum
medulla

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19
Q

What does the mesencephalon of the neural tube become

A

Midbrain

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20
Q

What does the prosencephalon of the neural tube become

A

Cerebrum
Thalamus

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21
Q

Further divisions of the prosencephalon, mesencephalon and rhombencephalon

A
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22
Q

What makes up the tri laminar disc composed of?

A

Ectoderm
Mesoderm
Endoderm

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23
Q

By what week of embryonic development can the three primary brain vesicles be identified?

A

By the end of week 5

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24
Q

Embryonic development of the ventricles

A

Telencephalon- Lateral ventricles

Diancephalan- Third ventricle

Metencephalon- Upper part of the 4th ventricle

Myelencephalon- The lower part of the 4th ventricle

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25
Q

What is spina bifida?

A

Failure of the tube to close in the spinal cord

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26
Q

What is anencephalus

A

Failure of the tube to close in the cephalic region

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27
Q

What layer of the trilaminar disc are the kidneys derived?

A

Intermediate mesoderm.

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28
Q

What are the names of the 3 paired kidneys that develop in the embryo?

A
  1. Pronephros.
  2. Mesonephros.
  3. Metanephros.
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29
Q

What does the mesonephros form?

A

The mesonephric ridge and duct.

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30
Q

What does the mesonephric duct form in the male?

A

The epididymis, vas deferens, seminal vesicles and ejaculatory duct.

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31
Q

What does the ureteric bud form?

A

The ureters, collecting duct, major and minor calyces and the renal pelvis.

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32
Q

What does the Müllerian duct form in females?

A

The uterine tubes, uterus, cervix and proximal 1/3 of vagina.

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33
Q

What is the cloaca divided into?

A
  1. Anorectal canal.
  2. Urogenital sinus.
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34
Q

What are the 3 parts of the urogenital sinus?

A
  1. Upper part.
  2. Pelvic part.
  3. Phalic part.
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35
Q

What part of the urogenital sinus is the bladder formed from?

A

The upper part.

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36
Q

What does the pelvic part of the urogenital sinus form?

A

The prostatic and membranous urethra.

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37
Q

What does the phalic part of the urogenital sinus form?

A

The penile urethra.

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38
Q

What part of the trilaminar disc are the bladder and urethra formed?

A

The endoderm.

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39
Q

What layer of the trilaminar disc forms the male and female genitalia?

A

Intermediate mesoderm.

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40
Q

What is the indifferent stage?

A

When the Wolffian and Müllerian ducts are both present. It is impossible to tell the sex of the embryo.

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41
Q

When are embryos no longer indifferent?

A

They are indifferent until the end of the 6th week.

42
Q

What causes the genital ridge to form ovarian tissue?

A

This happens by default due to the lack of a gonadal hormone influence. There is no Y chromosome and so no sex determining region and so no testis determining factor released.

43
Q

Why does the mesonephric duct degenerate in a female?

A

Due to the absence of testosterone.

44
Q

What does oestrogen stimulate?

A

The development of the female external genitalia and the differentiation of the Müllerian duct.

45
Q

What does the female external genitalia develop from?

A

The urogenital sinus.

46
Q

What does the urethral fold form in a female?

A

The labia minora.

47
Q

What does the genital tubercle form in a female?

A

The clitoris.

48
Q

What does the genital swelling form in a female?

A

The labia majora.

49
Q

True or False: the ovary lies behind the broad ligament.

A

True.

50
Q

What is the fornix?

A

The space between the cervix and the vagina.

51
Q

What is the hymen formed from?

A

The urogenital sinus.

52
Q

What is the primitive streak?

A

A depression in the epiblast.

53
Q

When do leydig cells start producing testosterone?

A

Week 8.

54
Q

What does testosterone stimulate?

A

Differentiation of the Wolffian duct.

55
Q

Why does the Müllerian duct degenerate?

A

Due to inhibiting substance being released from sertoli cells.

56
Q

What forms from degeneration of the Müllerian duct?

A

Utriculus prostaticus.

57
Q

What forms the phallus?

A

Elongation of the genital tubercle.

58
Q

What does the genital swelling form in a male?

A

The scrotum.

59
Q

What is meckle’s diverticulum a remnant of?

A

The vitelline duct - connected the midgut to the yolk sac.

60
Q

What is the significance of the Hilton white line?

A

It separates the non keratinised and keratinised epithelium in the anal canal.

61
Q

When does the anal membrane rupture?

A

In the 7th week. This allows the upper 2/3 to be continuous with the lower 1/3 of the anal canal.

62
Q

What layer of the trilaminar disc is the upper 2/3 of the anal canal derived from?

A

Endoderm.

63
Q

What layer of the trilaminar disc is the lower 1/3 of the anal canal derived from?

A

Ectoderm.

64
Q

What is the name of the structure that condenses in the intermediate mesoderm that gives rise to kidneys called?

A

Nephrogenic cords

65
Q

Where does the heart tube develop from?

A

Splanchnic layer of the lateral plate mesoderm

66
Q

What is the role of the endoderm in developing the heart tube

A

Secretes Vascular endothelial growth factor causing the lateral plate mesoderm to differentiate

67
Q

What does the mesoderm differentiate into? heart

A

Angioblast
Hemocytoblast

68
Q

What happens during lateral folding. heart

A

Through fusing 2 heart tubes become 1
2 pericardial cavities become 1

69
Q

What happens to the angioblast what does it develop into? heart

A

Angioblast-> Endothelial lining -> Endoderm

70
Q

Name the layers of the primitive heart tube, starting from the bottom

A

Blood flows into:
sinus venosus
primitive atria
primitive ventricle
bulbous cordis
truncus arteriosus
dorsal aortae

71
Q

What does the truncus arteriosus become?

A

Pulmonary trunk
Aortic arch

72
Q

What does the bulbus cordis become?

A

RV + outflow tract

73
Q

What does the primitive ventricle become?

A

LV

74
Q

What does the primitive atria become?

A

LA + RA

75
Q

Where does blood flow from into the sinus venousos when it is a primitive heart tube?

A

Common cardinal vein
Umbilical vein
Vitelline veins

76
Q

Stages of cardiac looping

A

TA + BC move down and to the right
PV moves upwards
PA moves backwards and outwards

77
Q

What makes up the endocardial cushions

A

Neural crest cells

78
Q

What the structure called when you fuse the post. and ant. endocardial cushions (heart)

A

Septum intermedium

79
Q

What happens when the septum intermedium is formed

A

Forms the right AV canal and the left AV canal

Forms valves on both sides of the septum (mitral valve/tricuspid valve apparatus) and a valvular annulus

This forms cordi tendinae

80
Q

What does the left hirn develop into?

A

Coronary sinus

81
Q

What does the right common cardinal vein develop into

A

Superior vena cava

82
Q

What happens in the elongation stage of midgut development?

A

Rapid elongation forms the primary intestinal loop. The proximal part of the loop forms the small intestine and the distal part forms the large intestine up to 2/3 TC.

83
Q

What happens in the herniation stage of midgut development?

A

The rapid growth of the intestinal loop means it is pushed into the extra embryonic cavity in the umbilical cord.

84
Q

What happens in the retraction stage of midgut development?

A

In the 10th week the herniated midgut returns into the expanded abdominal cavity. Th jejunum is first to return.

85
Q

What happens in fixation of midgut organs?

A

This is when some regions of the gut lose their dorsal mesentery. These regions become retroperitoneal.

86
Q

What happens in the rotation stage of midgut development?

A

The elongated intestinal loop rotates 270 degrees anticlockwise.

87
Q

What connects the midgut to the yolk sac?

A

The Vitelline duct.

88
Q

What are the 5 stages of midgut development?

A
  1. Elongation.
  2. Herniation.
  3. Rotation.
  4. Retraction.
  5. Fixation.

Easy Hores Rotate Round Fishermen

89
Q

What does the ventral mesentery become?

A

The lesser omentum.

90
Q
A

Blastocyst (day 4) ->

91
Q

What is the low oestrogen to progesterone during pregnancy responsible for

A

Implantation

92
Q

What develops into the placenta

A

Trophoblast

93
Q

What does trophoblast secrete

A

Human chorionic gonadotropin (HCG) happens around day 8

Tell the corpus luteum to keep secreting oestrogen and progesterone. This also suppresses other follicles from maturing

94
Q

What happens in the first trimester

A

Week 1 -13

Oestrogen + progesterone released by corpus luteum

HCG rises until it peaks before the end of the trimester and begins to degrade down.

The corpus luteum therefore shrivels and the placenta takes over

95
Q

What is the most abundant type of oestrogen

A

estriol

96
Q

Placenta and syncytiotrophoblast

A

Specialed trophoblast cells called the syncytiotrophoblast begin to secrete estriol and progesterone.

97
Q

What is human placental lactogen (hPL)

A

Inhibits insulin and makes sure there is a steady flow of glucose

98
Q

Does the haematocrit go up or down during pregnancy

A

Down

99
Q

Development of the placenta

A

Day 7-8, the foetus implants on the endometrial wall (decidua) and the area that it implants to is the decidua basalis.

Trophoblast cells from the outer layer can snuggle deeper into the decidua basalis. the foetus assembles into two layers of cells called the cytotrophoblast and the syncytiotrophoblast.

The cytotrophoblast is an inner layer of mononucleated cells. The syncytiotrophoblast is a multinucleated outer layer.

The syncytiotrophoblast does undergo cell division and just simply dies out over time. With the number of syncytiotrophoblast cells, there is a steady flow of cytotrophoblast. The cytotrophoblast fuses with the syncytiotrophoblast forming a syncytium.

The syncytiotrophoblast gets bigger going into the decidua basalis.

Around day 14 primary villi are formed cells begin to clear out between the primary villi leaving behind empty spaces called lacunae. Arteries fuse with lacunae and become filled with oxygenated blood. Veins bring blood back to the heart

Day 17: Foetal mesoderm cells form blood vessels in villi - connect with blood vessels in the umbilical cord.

The basal plate or the decidual plate is a thick layer of the decidua basalis where the spiral arteries and veins have to pass through to get to the junctional zone

In months 4/5 decidual septa form and divide the placenta into 15-20 regions known as cotyledons

100
Q

Foetal contribution to placenta

A

Chorionic plate

101
Q

Maternal contribution to placenta

A

Maternal arteries

102
Q

Chorionic cavity

A