Embryology - Respiratory System

Front 1

What forms the respiratory epithelium? What forms the rest of the respiratory tract?

Back 1

Epithelium - endoderm
the rest - splanchnic mesoderm

Front 2

Does the tracheal diverticulum separate completely from the foregut?

Back 2

No - it remains connected at the larynx

Front 3

How is the primitive streak formed?

Back 3

Cells from the epiblast migrate medially and towards one end (migrate first to rostral end - creates the rostral-caudal gradient of growth)

Front 4

Describe the process of Gastrulation (ie where do all the layers come from?)

Back 4

Epiblast cells that do NOT ingress for the Ectoderm
Epiblast cells that DO ingress form:
- the edoderm (by replacing the hypoblast cells)
- the mesoderm (by staying between the endoderm and the epiplast/ectoderm cells)

Front 5

The first cells to ingress through the primitive streak will form rostral or caudal structure?

Back 5

rostral

Front 6

How is the notocord formed? Which layers is it between?

Back 6

Cells ingress at Hensen's node and move rostrally (between the ectoderm and the endoderm)

Front 7

What is the fate of the ectoderm?

Back 7

becomes the nervous system, skin, hair, nails and glands.
contributes the neural tube

Front 8

How is the neural tube formed? (3 steps)

Back 8

Nerual plate --> Neural Tube
1. The notocord and adjacent paraxial mesoderm induce the above ectoderm to differentiate into the neural plate.
2. the edges of the neural plate elevate
3. edges make contact and the neural tube pinches off

Front 9

Where do neural crest cells come from and what do they become?

Back 9

They are at the edges of the neural plate. They migrate out into the mesoderm above the neural tube and become the DRganglion

Front 10

Identify the parts of the embryo

Back 10

These subdivisions of mesoderm run the length of the embryo

Front 11

Starting from the notocord and moving laterally, what are the subdivisions of the mesoderm?

Back 11

Paraxial - intermediate - lateral

Front 12

The lateral mesoderm divides into what? What is the area between these new layers called?

Back 12

Parietal/somatic mesoderm

Intraembryonic Coelom

Visceral/splanchnic mesoderm

Front 13

What can happen if trachea and foregut don't seperate?

Back 13

Tracheoesophageal fistula - the trachea can connect the to inferior portion of the esophagus (air down trachea into stomach)
Esophageal atresia - dead-end in the esophagus just above where the trachea connects to the esophagus.

Front 14

What could polyhydraminos be a sign of?

Back 14

obstruction in the gut of the baby - unable to swallow amniotic fluid d/t esophageal atresia.
May also occur in normal pregnancies for no obvious reason

Front 15

When do the alveoli begin development? When are they fully developed?

Back 15

Begins only once baby starts breathing. Finishes around age 8.

Front 16

Growth of the lungs depends on what 6 factors?

Back 16

- physical space in thorax (a hernia of the gut can impede this growth)
- presence of fetal lung fluid
- amniotic fluid
- fetal breathing movements
- phrenic nerve innervation
- hormonal influences

Front 17

What are the 3 main stimuli for breathing in the neonate?

Back 17

- Temperature (ie cold)
- Hypoxia (chemoreceptors have heightened sensitivity at birth d/t trauma)
- Pain (squishing through canal)

Front 18

What is the purpose of surfactant (ie what does it do?) 3 things

Back 18

- lowers surface tension
- stabilizes alveoli on expiration
- prevents epithelial tears

Front 19

Why do premies not have enough surfactant?

Back 19

They are either:
- too immature to produce any
- or, too immature to keep making surfactant after it is reabsorbed (cannot keep up supply to meet demand)

Front 20

How can you avoid respiratory failure in babies?

Back 20

Prevention - keep babe in utero, and "ripen" lungs with steroids at least 48hrs before birth
Give surfactant (real or artificial)