Embryology Exam 3 - Pre Class Review Questions

Which adult cavity is not originally present in the fetus?

Pleural Cavity - Around Lungs

What do we call a double layer of peritoneum which attaches a segment of gut to the body wall?

Mesentery

Which embryonic mesentery goes away?

Ventral Embryonic Coelom (Dorsal stays)

What folds separate heart from lungs?

Pleural Pericardial Folds

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Pleural Peritoneal folds become diaphragm

Generally describe the Diaphragm

dome shaped, most important for inspiration, develops from 4 components.

What are the 4 components the diaphragm is formed from?

Septum Transversum - Formed from central tendon

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Pleuroperitoneal Membranes - Grows ventromedially and fuses with septum transversum

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Dorsal mesentery of esophagus - Forms left and right crus of diaphragm

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Muscle of diaphragm - muscles of lateral walls growing over pleural perineal membranes.

The Diaphragm lies between the heart and liver. Is that where the septum transversum starts out?

No - Starts in neck region at C3, C4, C5 somite levels.

What nerve supplies the diaphragm?

Phrenic nerve

What condition can form in the diaphragm?

Congenital Diaphramatic Hernia

What are the effects of Congenital Diaphramatic Hernia

Defect is usually posterior or lateral, usually unilateral, intestines can stick through and into thorax, causes hypoplasia (underdeveloped lung)

What makes up the lower respiratory system?

Larynx, trachea, bronchi, lungs

What is the first part of the respiratory system to develop?

laryngo tracheal groove

What germ tissue develops epithelium, glands, ad visceral organs?

Endothelium

What germ tissue develops stroma, smooth muscle, walls of visceral organs, cartilage?

Splanchnic Mesoderm

What creates the tracheal esophageal folds?

Envaginates and forms respiratory bud, initially open communication between divertiulum and pharynx.

What does ventral laryngotracheal diverticulum form?

Respiratory System

What does dorsal laryngotracheal diverticulum form?

Esophogus (direct continuation of the pharynx)

All laryngeal cartilages except one develop from what?

4th and 6th pharyngeal arches

What does epiglotis develop from?

hypopharyngeal eminence

Do most mammals have a high or low larynx?

high (allows for swallowing and breathing at the same time)

When does the larynx descend in humans?

1\.5-2 yrs. (directly corollated with speech development)

Is infant a term for baby or a direct time period?

Time period (0-1yr)

What germ tissue will form tracheal respiratory epithelium and glands?

Endoderm

What forms c-ring cartilage and smooth muscle of trachea?

Splanchnic Mesoderm

What is an abnormal opening between the trachea and esophagus called?

Tracheoesophageal fistula (usually associated with Esophageal atresia - esophagus ends as blind pouch)

In lung development, which lung divides twice after the 2 primary buds form R/L?

Right one - which is why the right side has 3 lobes, left has 2.

What do we call functional independent subunits of the lung?

Segmental bronchus (surrounded by splanchnic mesoderm)

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*know this is important clinically*

What forms broncho pulmonary segments?

Splanchnic Mesoderm

What forms parietal pleura?

Somatic Mesoderm

What are the 4 stages of lung development and what marks each?

1. Weeks 6-16 - Pseudoglandular Stage -- all major parts of lungs formed except those to do with gas exchange. Babies born at this stage cannot live.
2. Weeks 16-26 - Cannalicular Stage -- Enlargement of bronchi, getting bigger, more vascular, alveoli forming here.

Babies at this stage can live if 24-26 weeks.
3. Weeks 26-birth - Terminal Sac Stage -- Forming primordia of alveoli, cells involved in gas exchange, flat Type 1 pneumocytes(alveolar cells) and Type 2 pneumocytes, cells are rounded and secrete surfactant.

Surfactant begins to form at 20-22, reaches adequate levels at 26-28.
4. 32 weeks to 8 years - Alveolar stage - most alveoli form post birth, most formed by age 3 *reason parents should not smoke around infants/children*… among other reasons not to smoke.

What are the 3 factors that determine if a fetus will make it from placental respiration to breathing without a placenta?

1. Adequate surfactant
2. Formation of functional alveoli
3. Pulmonary circulation established

Is baby breathing on an ultrasound?

No, those are called fetal breathing movements.

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Important for building up muscles of respiration and lung development.

At/around time of birth, how are lungs cleared of amniotic fluid?

Expulsion during parturition, blood vessels, lymphatics.

What is it called when there is not enough amniotic fluid?

Oligohydromnios

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*related to pulmonary hypoplasia → due to mechanical compression in utero*

What causes RDS?

Surfactant Deficiency

The digestive system starts out closed. What are the two ends called?

Cranial end - Oropharyngeal membrane

Caudal end - Cloacal membrane

What is the digestive system formed from in regards to germ layers?

All 3 germ layers (Endoderm, ectoderm, mesoderm)

Main one: Endoderm (epithelium and paranchama of organs)

Other two: Splanchnic mesoderm (smooth muscle and connective tissue)

Ectoderm (Cranial and caudal ends)

What is the artery of the foregut?

Celiac trunk

What are the muscles of the esophagus?

Upper 1/3 - Striated

Middle - Mixed

Lower 1/3 - Smooth

What condition is polyhydromnios associated with?

Esophageal Atresia

The stomach is a dilation of what?

The foregut

Which section of the stomach forms fastest?

Dorsal - greater curvature of stomach

What does the ventral mesentary of the stomach form?

Ventral mesogastrium

What does the dorsal mesentary of the stomach form?

Dorsal mesogastrium

*spleen develops here as well*

Stomach Rotation

Rotates 90 degrees clockwise when viewed cranially.

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ventral becomes R side, dorsal becomes L side

L surface becomes ventral, R surface becomes dorsal

What is the Omental Bursa?

Dorsal mesogastrium elongates on rotation, causing a cavity to form.

What forms the Greater Omentum

The fusing of the dorsal mesogastrium.

What does the ventral mesograstrium become?

Lesser omentum and part of the liver(falciform ligament of the liver).

What does the Duodenum come from?

Foregut and Midgut (delineation is where the bile duct enters)

What is the blood supply for the Duodenum?

The celiac trunk supplies above the bile duct.

The superior mesentaric artery supplies below the bile duct.

What do the liver and biliary systems develop from?

Hepatic Diverticulum

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Large cranial part forms liver

Small caudal part forms gallbladder

Stalk forms biliary duct system

What germ tissue gives rise to paranchyma?

Endoderm

What gives meconium its green color?

Bile production in liver

What two things does the pancreas develop from?

1. Ventral bud and mesentary - lower head and uncinate process


1. Dorsal bud and mesentary - everything else, it’ bigger, more significant.

What forms the main and accessory ducts of the pancreas in adults?

Proximal part of dorsal ducts.

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*ADPD*

What is Annular Pancreas?

If ventral duct becomes biforcated and goes on both sides of duodenum, it constructs it, causing this.

What organ develops from mesenchyme between 2 layers of the dorsal mesogastrum

Spleen

What happens to the spleen when the stomach rotates?

It rotates and ends up left of the stomach.

What does the midgut form?

Everything from where the bile duct comes in to duodenum through R most 2/3 of transverse colon.

What is the blood supply to the midgut?

Superior mesenteric artery

What is caused due to the midgut growing faster than the body cavity?

Physiological umbilical herniation - Intestines leave body at 6 weeks and return at 10 weeks.

Which part of the intestines grows faster?

Cranial Limb - Small Intestines

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Caudal Limb - Large Intestines - SLOWEST

Explain intestinal rotation

Rotates 90 degrees counterclockwise, cranial goes to the R, caudal to L. Small Intestines retract first into middle of abdominal cavity, large intestines follow. THEN, they rotate again 180 degrees counterclockwise. TOTAL = 270 degrees.

What is the last part of large intestine to enter the abdominal cavity?

Secum

What is it called if there is a 12 week ultrasound and the intestines are still outside the abdomin?

Omphalocele

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*50% of these cases have additional chromosomal defects*

What mimics appendicitis?

Ileal (Meckel’s) Diverticulum

What does the hindgut form?

Digestive tract from lower 1/3 of colon through the upper part of the anal canal.

What artery supplies hindgut?

Inferior mesenteric artery

What is the expanded chamber at the end of the hindgut that lined with endoderm?

Cloaca

Upper 2/3 of the anal canal is derived from what germ tissue?

Endoderm

What forms the lower 1/3

Ectoderm

What is the boundary between?

Pectinate Line

What is Anal Atresia?

Anal canal ends at pectinate line as blind pouch

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requires surgery

What is the first organ system to become functional?

Cardiovascular -- Appears during 3rd week.

The heart starts out with how many tubes and where?

2 - lateral mesoderm

Endothelial heart tube forms what?

Endocardium (inner layer)

During right hand looping of heart, what happens?

Bulbus cordus ends up on the right

ventricle ends up on the left

atrium is pulled up behind

apex points to left

What do we call a heart that folds to the left instead of right?

DextroCardia - heart reversed in position.

Do we want situs inversus along with Dextrocardia?

Yes - we want everything flipped if something is going to be flipped.

Blood enters what chamber first through 3 sets of veins?

Sinus Stenosum → Atrium → Ventricle → bulbus cordus

The ventral and dorsal walls of the heart thicken and bulge towards lumen, what do we call those bulges?

Endocardial Cushions

The cardiac bulges fuse to form 2 canals. Which is first and what do they form?

1st - grows down to roof of atrium - forms septum premium

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What does the septum premium fuse with?

Endocardial cushions

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leaves a gap called foramen premium

When foramen primium closes, what second hole opens?

Foramen secundum

After foramen secundum, what wall is formed?

Septum secundum

What does septum secundum create?

Rigid wall, creates one way valve, directs blood from R to L.

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*at birth or right after, this should be shut*

What is it called when the foramen ovale shuts at birth?

Fossa Ovalus

What is it called if fossa ovalus does not shut?

Atrial Septal Defect

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*If it’s not causing problems it’s called patent foramen ovale, 25% of population has this*

What is the most common defect of the heart?

Ventricular septal defects

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*usually in membranous part*

What is the end of the Bulbus Cordus called?

Trunkus arteriosus

What does the Trunkus arteriosus form?

2 great arteries of the heart:

* Aorta
* Pulmonary Trunk

What is the Tetrology of Fallot?

4 Cardiac Defects Together:


1. Pulmonary Artery Stenosis
2. Ventricular Septal Defect
3. Enlarged Aorta
4. Right Ventricle Hypertrophy

What happens if the division of uneven in Aortic Looping?

Tetralogy of Fallot -- ends up with a larger aorta, and smaller venous systems.

What part of the heart is formed by migrating neural crest cells?

Trunkus Arteriosus

What other body parts do we look at to hint at possible neural crest migration issues?

Face and Ears (often go with heart defects)

Sinus Venosus

Start as one of 4 chambers of embryonic heart. Will form 2 horns -

L = coronary sinuses

R = sinus venarum

How does oxygenated blood get to fetus?

Umbilical Veins

What structure allows 50% of blood to bypass the liver during embryological development?

Ductus Venosus

Which vessels will carry deoxygenated blood from fetus back to placenta?

Umbilical artery

Through what opening does blood pass from the R atrium to the L in fetus?

Foramen Ovale