Anatomy Exam 4: Development Of Body Cavities

Front 1

During the 3rd week of development the intraembryonic mesoderm on each side of the midline differentiates into what 3 mesoderms?

What do these 3 germ layers form?

Back 1

1. paraxial
2. intermediate
3. lateral

-form the trilaminar germ disc

Front 2

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Describe the formation of the intraembryonic cavity within lateral plate mesoderm

Back 2

lateral plate mesoderm divides into 2 layers:
-somatic/parietal mesoderm
-splanchnic/visceral mesoderm
Space btwn these layers = intraembryonic cavity
-initially right & left intraembryonic cavities on each side of midline
--> merge into single intraembryonic cavitiy
(goes from throacic region to pelvic region)

Front 3

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Describe the division of the single intraembryonic cavity into the pericardial, pleural, and peritoneal cavities

Back 3

Once the left/right intraembryonic cavity has merged into a single cavity, it will go on to subdivide into three cavities surrounding important structures, later in development
-pericardial cavity (around heart)
-plueral cavities (one around each lung)
-peritoneal cavity (around abdominal organs)

Front 4

During abdominal development, the temporary primitive umbilical ring is caused by what 2 structures?

What will this area become?

Back 4

(5 wk embryo on left, 10 wk on right)

1. the vitelline duct
(connection btwn midgut & yolk sac)
2. connecting stalk


-becomes umbilicus

Front 5

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Discuss development of the serous membranes lining the body cavities

Back 5

cells lining the intraembryonic cavity form a thin layer --> serous (mesothelial membrane)

part that develops from parietal mesoderm = parietal layer (lines inside of body wall)

part that develops from visceral mesoderm = visceral layer (covers heart, lungs, abdominal organs)

Front 6

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Innervation of serous membranes lining body cavities

Back 6

parietal layer of serous membrane:
anterior abdomen- T7-12 & L1
central diaphram- phrenic nerve
peripheral diaphram- T7-12 (lower intercostal nerves)
pelvic region- obturator nerve

visceral layer of serous membrane:
sensory innervation from autonomic afferent nerves

Front 7

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function of mesenteries for the peritoneal cavity

Back 7

-Parietal & visceral layers of peritoneum (in abdomen) are continuous at dorsal mesentary
-Mesentary is a double layer of peritoneum that provides a pathway for blood vessels, nerves, & lymphatics to reach abdominal organs *

Front 8

The pericardial cavity and the pleural cavity are separated by the development of what membrane?
Why does this membrane develop?

Back 8

separated by pleuropericardial membranes, which develop as a result of the lungs growing into the body wall on each side, segmenting the intraembryonic cavity

Front 9

What forms to separate the thoracic and abdominal cavities?

Back 9

respiratory diaphram

Front 10

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Describe the formation of the respiratory diaphragm

Back 10

The diaphram develops from the following sources:
-septum transversum--> central tendon
-pleuroperitoneal membranes
-dorsal mesentery of the esophagus (btwn membrane)
-mesoderm (ingrowth) of the body wall

Front 11

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Describe the embryological basis for the innervation of the respiratory diaphram

Back 11

-septum transversum: C3-5, phrenic nerve
(phrenic supplies all diaphram EXCEPT peripheral sensory)

-sensory of peripheral portion (developed from mesoderm of body wall) of diaphram: GSA from lower intercostal nerves

Front 12

What is the septum transversum and how does its position change as the embryo develps?

Back 12

-it is a plate of mesodermal tissue that initially lies opposite cervical somites
(innervated by C3-5)
-repositioned caudally by cephalocaudal folding due to differential growth
-lies btwn developing heart in thorax & liver in abdomen
-forms the central tendon of the diaphram

Front 13

What is differential growth?

Back 13

the vertebral column and associated tissues grow more rapidly than the ventral part of embryo

Front 14

Development of the septum transversum leaves holes btwn thoracic & abdominal cavities, the _________________, on each side of the foregut
How are these holes closed?

Back 14

-pericardioperitoneal canals

-closed by development of pleuroperitoneal folds, that fuse w/ septum and dorsal mesentary of esophagus

Front 15

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Discuss the development of congenital diaphragmatic hernias and their clinical importance.

Back 15

-the defect (foramen of Bochdalek), most frequently results from failure of one or both pleuroperitoneal membranes to close the pericardioperitoneal canals
* one of the most common malformations of newborns (1:2000), can sometimes be repaired in utero

Front 16

Where do congenital diaphragmatic hernias most commonly occur?

Back 16

on left side in region of the lumbocostal trigone

Front 17

What is the result of a congenital diaphragmatic hernia?

Back 17

-allows loop of intestine, stomach, spleen, and/or part of liver to enter thoracic cavity
-results in pulmonary hypoplasia* (fatal, unless repaired in utero)

Front 18

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Describe developmental defects of the ventral body wall.

Back 18

*result from failure of body folding or failure of fusion of lateral body wall folds in anterior midline

Ectopia cordis- the lateral body folds fail to fuse in the thoracic midline = heart lies outside body

Omphalocele- failure of the midgut to return to the body cavity following physiological herniation = viscera covered by amnion (w/i sac), high alpha-fetoprotein levels present

Gastroschisis- loops of bowel herniate through weak body wall lateral to umbilicus = NOT covered by amnion, high alpha-fetoprotein levels present in maternal serum & amniotic fluid

Front 19

As a result of cephalocaudel & lateral folding of trilaminar germ disc, most of the __________ is incorporated into the GI tract, which consists of foregut, midgut, & hindgut

Back 19

secondary yolk sac

Front 20

The respiratory diverticulum/long bud is an outgrowth from the ventral wall of the __________. It's epithelial lining has an _______________ origin, while the rest of it's components are derived from _____________mesoderm.

Back 20

foregut

endodermal origin

splanchnic mesoderm

Front 21

Longitudinal trachesophageal ridges fuse to form the _________________________. This separates the esophagus from what?

Back 21

tracheosophageal septum

separates esophagus (foregut) from trachea (long bud)

Front 22

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Describe development of the respiratory system

Back 22

-long bud/respiratory diverticulum forms (4 wks)
-long bud separates from foregut when tracheosophageal septum forms
-separation differentiates esophagus (dorsally) & trachea (ventral)
-laryngeal inlet/orifice maintains communication btwn respiratory primordium & pharynx

Front 23

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Respiratory system, developmental defects that may occur.

Back 23

Esophageal Atresia: 90% the upper part of the esophagus ends in a blind pouch w/ lower segment forming a tracheoesophageal fistula

Tracheoesophageal fistula: connection btwn the trachea & esophagus-->pneumonia & polyhydramnios

Front 24

The epithelial lining of the larynx originates from endoderm, in contrast the cartilage & muscles originate from _______________.

Back 24

mesenchyme of the 4th & 6th pharyngeal arches

Front 25

The intrinsic muscles of the larynx are innervated by ___________

Back 25

vagus nerve (C10)

Front 26

The long bud forms the trachea, which further divides into 2 bronchial buds. The bronchial buds enlarge to form what?

Back 26

the right and left primary bronchi

Front 27

Which primary bronchi is more susceptible to inhalation of foreign objects and why?

Back 27

right primary bronchi, it is wider & more vertically oriented

Front 28

Right primary bronchus form __ secondary (lobar) bronchi & the left form __.
Each lobar bronchus branches into _________________, each of which supplies a bronchopulmonary segment.

Back 28

right 3
left 2

branch into tertiary (segmental) bronchi

Front 29

The conducting portion of the bronchial tree ends with ___________________
The respiratory portion of the bronchial tree begin with __________

Back 29

ends w/ terminal bronchioles

begins w/ respiratory bronchioles

Front 30

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Discuss the formation of alveoli

Back 30

Respiratory bronchioles divide into alveolar ducts
--> alveolar ducts end in alveolar sacs
--> alveolar sacs have alveoli (air spaces where gas exchange occurs)

Front 31

Alveoli are lined w/ 2 main cells types of squamous epithelium:

Back 31

1. type 1 pneumocytes
-flattened cells
-attenuated w/ cytoplasm
-90% of surface lining
2. type 2 pneumocytes
-round cells
-located in obtuse angles of alveoli
-secrete surfactant

Front 32

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Discuss role of surfactant in alveoli

Back 32

reduces alveolar surface tension

Front 33

Stages of Lung Maturation

Back 33

Psuedoglandular period : 5-16 weeks
Canalicular period: 16-26 weeks
Terminal sac period: 26 weeks to birth
Alveolar period: 8 months to childhood

Front 34

What occurs during the pseudoglandular period?

Back 34

branching continues to form terminal bronchioles
(no resp. bronchioles or alveoli yet)

Front 35

What occurs during the canalicular period?

Back 35

terminal bronchioles divide into 2 or more respiratory bronchioles which each divide into 3-6 alveolar ducts

Front 36

What event in lung maturation is key to survival and begins at about 26 weeks?

Back 36

terminal sacs (primitive alveoli) form
capillaries form close contact

*Terminal sac period

Front 37

what occurs during alveolar period?

Back 37

mature alveoli have well developed epithelial endothelial capillary contacts

Front 38

Pleural cavities are partitioned from rest of intraembryonic coleom by formation of ________________ and ________________

Back 38

pleuropericardial membranes
(btwn pericardial & pleural cavities)
and
pleuroperotpneal folds
(btwn plueral & peritoneal cavities)

Front 39

Splanchnic mesoderm covering outside of lungs forms (visceral/parietal) pluera, which is innervated by ___________________

Back 39

visceral

GVA fibers from pulmonary plexuses

*insensitive to pain

Front 40

Somatic mesoderm covering inside of body walls forms (visceral/parietal) pluera, which is innervated by ___________________

Back 40

parietal

GSA fibers from intercostal nerves

*very sensitive to pain

Front 41

Potential space btwn visceral & parietal pluerae is ___________

Back 41

pleural cavity

Front 42

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Discuss factors necessary for normal lung development.

Back 42

necessities:
-fluid in the lungs
-fetal breathing movements
-adequate amniotic fluid volume (space for growth)

Front 43

At birth, lungs are 1/2 filled w/ fluid, fluid is cleared via 3 routes:

Back 43

1. pressure on fetal thorax
(during delivery, fluid comes out of mouth & nose)
2. resorption into pulmonary capillaries
3. resorption into pulmonary lymphatic vessels

Front 44

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Discuss the cause of respiratory distress syndrome (hyaline membrane disease)

Back 44

cause: insufficient synthesis of surfactant by type II alveolar cells (pneumocytes)

leads to: increase in surface tension & collapse of alveoli, common cause of premi death*

-can be treated w/ maternal glucocorticoid therapy or artifical surfactant adiministration to infant

Front 45

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Discuss the causes of hypoplastic (underdeveloped) lungs

Back 45

cause:
-oligohydramnios, prevents expansion in thoracic cavity
-congenital diaphragmatic hernia, most common cause
leads to: underdeveloped lungs