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MTM > Embryology Week 3 > Flashcards

Embryology Week 3 Flashcards

1
Q

Development of the lungs

A
  • Respiratory diverticulum develops into 2 primary bronchial buds
  • Lobar bronchi develop from primary buds (2 on left, 3 on right)
  • Lobar bronchi divide continuously until terminal bronchioles are formed (week 28)
  • Respiratory bronchioles branch off terminal bronchioles
  • Terminal sacs at ends of respiratory bronchioles are primitive alveoli
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2
Q

What are the 2 horseshoe shapes of island cells to become blood vessels and where are they found?

A
  • Endocardial tubes (outside)
  • Dorsal aortae (inside)
  • Both found in visceral lateral plate mesoderm
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3
Q

What happens to the endocardial tubes on day 22?

A
  • They have moved to the midline with embryonic folding, ventral to the gut tube
  • They fuse
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4
Q

Structures of the heart at day 23

A
  • Sinus venosus
  • Atrium
  • Ventricle
  • Bulbus cordis
  • Aortic roots
  • Aortic arches
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5
Q

How does the heart twist in week 4?

A
  • Bulbus cordis moves ventrally and right
  • Atrium tucks up behind ventricle and left
  • Called cardiac loop
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6
Q

How many pairs of aortic arches are there when the heart twists and which will remain as the aorta eventually?

A
  • Pair 1, 2, 3, 4, 6
  • Left 4th will become aorta
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7
Q

3 sections of divided bulbus cordis

A
  • Truncus arteriosus (aorta + pulmonary trunk precursor)
  • Conus cordis (outflow tract of both ventricles precursor)
  • Primitive right ventricle
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8
Q

What does the ventricle of the original heart tube become after twisting?

A

Primitive left ventricle

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9
Q

What does the atrium of the original heart tube become after twisting?

A

Primitive right and left atria

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10
Q

What brings blood from the veins into the primitive right atrium?

A

Sinoatrial orifice

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11
Q

What grows upwards to begin dividing the 2 ventricles?

A

Muscular interventricular septum

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12
Q

What carries blood from the atria to the ventricles?

A

Atrioventricular canal

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13
Q

What growths occur in the atrioventricular canal and what do they do?

A
  • Endocardial cushions
  • Separate it into left and right canals
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14
Q

How do the atria begin to divide?

A
  • Septum primum grows down from left atrium ceiling (ostium primum under it allows blood flow)
  • Holes begin to appear at top and connect to form ostium secundum when septum primum reaches the endocardial cushions
  • Septum secundum grows down from right atrium ceiling
  • Gap under it is foramen ovale to allow blood flow
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15
Q

What growths separate the truncus arteriosus and conus cordis in 2?

A

Conotruncal ridges (become conotruncal septum)

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16
Q

How are the ventricles finally separated?

A

Conotruncal septum fuses with muscular interventricular septum

17
Q

What 2 channels are formed by the conotruncal septum and where do they receive blood from?

A
  • Pulmonary channel (right ventricle)
  • Aortic channel (left ventricle)
18
Q

What veins does sinus venosus originally receive blood from?

A
  • Common cardinal vein
  • Umbilical vein
  • Vitelline vein
19
Q

Development of the circulatory system

A
  • Vitelline veins forms network called hepatic sinusoids
  • Proximal parts of umbilical veins disappear and they drain into hepatic sinusoids
  • Distal right umbilical vein disappears
  • Ductus venosus carries blood from left umbilical past liver to right hepatocardiac channel
  • Distal left vitelline vein disappears
  • Right vitelline now called superior mesenteric vein
  • Portal vein drains blood from liver to IVC
20
Q

Development of nephric tubules and glomeruli

A
  • Blind-ended tubules develop in the intermediate mesoderm
  • Branches of dorsal aorta form capillary knots at the nephric tubules
21
Q

Parts of the intermediate mesoderm (cranial to caudal)

A
  • Pronephros
  • Mesonephros
  • Metanephros
22
Q

What connects the mesonephros to the cloaca?

A

Mesonephric duct

23
Q

What connects the metanephros to the mesonephric duct?

A

Ureteric bud

24
Q

Development of a kidney

A
  • Ureteric bud connects to metanephros at renal pelvis
  • Ureteric bud branches into metanephros forming major calyxes
  • Minor calyxes branch off major calyxes
  • Collecting tubules branch off minor calyxes
  • Metanephric tissue condenses to form nephrons with a Bowman’s capsule at the end opposite the collecting tubule
  • Tissue layers fuse between nephron and collecting tubule
25
Q

Movement of ureteric bud

A
  • Eventually opens directly into urogenital sinus
  • Switches place with mesonephric duct to be above it
26
Q

What is the gonadal ridge and what happens to it?

A
  • Block of tissue formed on mesonephros
  • Epithelium of it grows inwards, making sex cords
  • Primordial germ cells migrate into the sex cords
27
Q

How is sex determined?

A
  • Sex-determining region of Y gene codes for the SRY protein
  • This wakes up SOX9 gene on chromosome 17
    > Turned on in both males and females, but silenced in females
  • WNT4 gene silenced in male gonads but unleashed in female gonads
28
Q

Female gonadal development

A
  • Sex cords replaced by cortical cords
  • Cortical cords form primordial follicles around germ cells
  • Germ cells start meiosis but don’t complete process until they begin to form ova during ovulation
29
Q

Male gonadal development

A
  • SRY expressed in testis cords
  • Cords remain solid until puberty, where they become hollow and form seminiferous tubules
  • Sertoli cells produce growth factor causing Leydig cells to differentiate
30
Q

What are paramesonephric ducts?

A
  • Run next to mesonephric ducts
  • Open at top end into intraembryonic cavity
31
Q

Fate of (para)mesonephric ducts in females

A
  • Mesonephric ducts regress
  • Paramesonephric ducts fuse at caudal end to form uterovaginal canal (forms upper vagina and uterus - eventually fuses with outgrowths of urogenital sinus which forms lower vagina)
  • Open ends of paramesonephric ducts become oviducts
32
Q

Fate of (para)mesonephric ducts in males

A
  • Paramesonephric ducts regress
  • Mesonephric duct forms ductus deferens
  • Seminal vesicles bud of ductus deferens
  • Prostate and bulbourethral glands bud of urethra

MTM (19 decks)

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