Development of the respiratory system

Question 1

What does the ectoderm develop and what does this have?

Answer 1

develops a neural groove and the tips of the walls of this groove are called the neural crest

Question 2

What does the lateral plate mesoderm divide into?

Answer 2

2 layers

• parietal (somatic)
• Visceral (splanchnic)

Question 3

What does the parietal layer of mesoderm form?

Answer 3

body walls

Question 4

What does the visceral layer of lateral plate mesoderm form?

Answer 4

surround the organs

Question 5

What does the parietal layer of the lateral plate mesidern ‘merge’ with?

Answer 5

ecotderm

Question 6

What two processes occur during lateral folding of the trimlaminar embryo?

Answer 6

1. primitive tolk sac becomes “pinched”. Primitive yolk sac will become the digestive tract or the gut tube. While this takes place, the visceral layer of the lateral plate mesoderm will envelope to the future gut tube
2. The leading edge of the ectoderm and the pariteal layer of lateral plate mesoderm will move antero-medially

Question 7

Draw a diagram illustrating what happens during lateral folding of the trilaminar embryo

Answer 7

Question 8

Draw a diagram of the trilaminar embryo

Answer 8

Question 9

What fuse together in the ventral mid line at the end of lateral folding?

Answer 9

parietal layer of lateral plate mesoderm and ectoderm

Question 10

What becomes the parietal pleura?

Answer 10

parietal layer of lateral plate mesoderm

Question 11

What are the main features of the embryo at the end of lateral folding

Answer 11

1. a cavity (the coelom) which will become the thoracic abdominal cavity (the cavities are continuous cia the pericardio-peritoneal canals until the diaphragm forms)
2. A body wall (thoracic wall) made out of a surface of ectoderm and pariteal layer of lateral plate mesoderm deep to it
3. The gut tube, suspended by visceral layer of lateral plate mesoderm

Question 12

What also occurs while lateral folding is taking place?

Answer 12

cranio-caudal folding

Question 13

Draw what an embryo looks like at the end of lateral folding of the trilaminar embryo

Answer 13

Question 14

What happens when the embryo is about 4 weeks old?

Answer 14

In the cervical portion of the gut tube, in the ventral midline, the respiratory diverticulum starts to appear

Question 15

How does the respiratory diverticulum expand?

Answer 15

Ventrally and towards the chest, in front of the gut tube

Question 16

How is the respiratory diverticulum separated from the gut tube?

Answer 16

trans-eosphgeal ridges grow towards each other

Question 17

What does the diverticulum bifurcate into? And what subsequently happens?

Answer 17

2 branches

later these 2 branches expand and dilate. terminal ends of these dilations are called lung buds that will become lungs

Question 18

What does the gut tube into?

Answer 18

the digestive tract between the mouth and the anus

Question 19

When do pharyngeal arches start to appear?

Answer 19

4th-5th weeks of development

Question 20

What are pharyngeal arches separated by?

Answer 20

pharyngeal clefts

Question 21

How many pharyngeal arches are there? How are they numbered and what elements do they contain?

Answer 21

5

Numbered 1,2,3,4,6

• cartilaginous element
• an artery (aortic arch)
• a nerve (Cranial)

Question 22

What is maintained even though the tracheo-esophgeal septum separated the gut tube from the upper respiratory tract

Answer 22

laryngeal opening

Question 23

What does the upper end of the respiratory diverticulum become?

Answer 23

larynx

Question 24

What does the middle section of the respiratory diverticulum become?

Answer 24

trachea

Question 25

What does the lower end of the respiratory diverticulum become?

Answer 25

tertiary bronchi, broncioles and the alveoli

Question 26

What does the bronchial tree push against as it grows and expands?

Answer 26

visceral layer of lateral plate mesoderm; which develops into visceral pleura

Question 27

Where is the epithelium of the respiratory system derived from?

Answer 27

endoderm

Question 28

The lung develops in 4 overlapping stages. What are these?

Answer 28

1. Pseudoglandular 2. Canalicular 3. Terminal Saccular 4. Alveolar

Question 29

What 2 stages are no compatible with life?

Answer 29

1. Pseudoglandular 2. Canalicular

Question 30

What secretes surfactant? And from when?

Answer 30

type 2 pneumocytes from 20 weeks

Question 31

From when can the foetus survive?

Answer 31

28 weeks

Question 32

What are the four sources of origin of the diaphragm?

Answer 32

1. pleura-peritoneal folds 2. pleura-peritoneal folds fuse with septum transversum 3. Mesentary of the oesphagus 4. Muscular in-growth from the body wall

Question 33

What does the septum transversum form?

Answer 33

the central tendon of diaphragm contains myoblasys frim the somites in C3,4,5 (phrenic nerve)

Question 34

What do the crura develop from?

Answer 34

mesentary of the oesphagus

Question 35

What causes a diaphragmatic hernia

Answer 35

failure of fusion

Question 36

Explain the 5 types of tracheo-esophgeal fistula

Answer 36

A + B = congenital abnormalities of the trachea and oesophagus, there is communication between the trachea and oesphagus, usually companied by esophageal atresia (gut = disconnected) C, D + E = When the baby attempts to feed milk enters the trachea causing choking and possibly pneumonia. there is also the potential for retrograde passage of gastric acid from the GI tract into the respiratory system

Question 37

What is the most common congenital disorder of the respiratory system?

Answer 37

oesophgeal atresia

Question 38

What occurs in oesophgeal atresia?

Answer 38

During a normal pregnancy, the foetus swallows amniotic fluid which is resorbed from the gut and returned to the maternal circulation If oesophageal atresia develops, this circulation of fluid is prevented and polyhydramnios develops (excess amniotic fluid)

Question 39

What are the 3 different types of diaphragmatic hernia?

Answer 39

Question 40

What causes respiratory distress syndrome?

Answer 40

deficiency in surfactant