Embryology Study Material for Week 6 - Key Terms and Definitions

What 3 regions does the mesoderm split into?

Lateral plate mesoderm

Intermediate mesoderm

Paraxial mesoderm

Different inhibition of what gene causes the differentiation of mesoderm into 3 layers?

BMP-4

Which 3 genes inhibit BMP-4?

Noggin

Chordin

Cerberus-1

Which layer of the mesoderm is exposed to the highest level of BMP-4 inhibition?

Paraxial mesoderm

Which layer of the mesoderm are exposed tot he lowest level of BMP-4 inhibition?

Lateral plate mesoderm

Which layer of the mesoderm is exposed to intermediate amounts of BMP-4 inhibition?

Intermediate mesoderm

What gives rise to the axial skeleton?

Paraxial mesoderm

Which parts of the skeleton are formed by the paraxial mesoderm?

Cranial region

Occipital region

Cervical region

Trunk

What are the segments of the trunk?

Thoracic

Lumbar

Sacral

Coccygeal

What is the term for the blocks of epithelial tissue formed by the mesoderm?

Somitomeres and somites

What is the AKA of the intermediate mesoderm?

Intermediate mesenchyme / nephrotome

Which part of the body does the intermediate mesoderm not form in?

Cranial region

Which layer of the mesoderm gives rise to the urogenital system?

Intermediate mesoderm

What are the components of the urogenital system?

Kidneys

Certain parts of the adrenal gland

ureters

bladder

gonads (testes and ovaries)

urethra

What is the AKA of the urogenital system?

Nephritic structures

What is the AKA of the lateral plate mesoderm?

Lateral mesoderm / Lateral intraembryonic mesoderm

What structures are formed by the lateral mesoderm?

Cardiovascular system

Heart

Blood

Smooth muscle

Limbs of the skeleton

What is the key identifying factor of the lateral mesoderm?

High levels of BMP-4

Which layer of the mesoderm does not segment due to excessive BMP-4 levels?

Lateral mesoderm

What is the dividing line between the caudal and cranial regions of the lateral mesoderm?

Fifth somite

T or F: the Lateral mesoderm is divided biochemically, but not physically

True

What does the cranial division of the lateral mesoderm form?

Heart (contains the cardiac progenitor cells)

Dorsolateral neck muscles

What does the caudal division of the lateral mesoderm form?

bones/ligaments/tendons of the upper and lower extremties

What is the term for the cystic cavities that form in the lateral plate mesoderm?

Coelomic spaces

What do the coelomic spaces merge to form?

Intraembryonic coelom

What is the AKA of the intraembryon ic coelom?

Embryonic body cavity

What two layers are formed by the creation of the intraembryonic coelom?

Somatic lateral plate mesoderm

Splanchnic lateral plate mesoderm

Which 3 body cavities are formed by the lateral plate mesoderm?

Pericardial cavity

Pleural cavity

Peritoneal cavity

What are the 3 layers of the pericardium?

Fibrous pericardium

Parietal serous pericardium

Visceral serous pericardium

What is the AKA of the visceral serous pericardium?

Epicardium

What part of the lateral plate mesoderm is the pericardial cavity derived from?

Intraembryonic coelom

What is the space between the parietal and visceral pleura of the lungs called?

Pleural cavity

What type of tussle are the pleura, pericardium, and peritoneum made of?

Mesothelial tissue

What are the AKAs of the somatic lateral plate mesoderm?

somatic mesoderm

parietal mesoderm

parietal lateral plate mesoderm

somatic intraembryonic mesoderm

soamtopleuric mesoderm

What are the AKAs of the Splanchnic lateral plate mesoderm?

Parietal mesoderm

Visceral mesoderm

Visceral lateral plate mesoderm

Splanchnic intraembryonic mesoderm

Splanchnopleuric mesoderm

What layer of the lateral mesoderm is adjacent to the ectoderm (outer layer)?

Somatic

Which layer of the lateral mesoderm is adjacent to the endoderm (inner layer)?

Splanchnic

What is do the somatic lateral mesoderm and ectoderm join to form?

somatopleuric mesoderm

What is the AKA of the somatopleuric mesoderm?

somatopleure

What do the endoderm and splanchnic lateral plate mesoderm join to form?

Splanchnopleuric mesoderm

What is the AKA of the splanchnopleuric mesoderm?

splanchnopleure

What forms the muscular connective tissue layer of the gut tube?

Splanchnic lateral plate mesoderm

What forms the epithelial layer of the gut tube?

Ectoderm

What are the muscular connective tissue layers of the gut tube?

Lamina propria

Muscularis mucosae

Submucosa

Muscularis externa

Adventitia

What are the components of the mucosal layer of the gut wall?

Endothelium

Lamina propria

Muscularis mucosa

Which layer of the gut wall contains the bigger blood vessels, nerves, and lymph?

Submucosa

What is the outermost layer of the GI tract?

Adventitia layer

What is the progenitor of the endocardium?

Endoderm

What are the three members of the respiratory unit?

Respiratory bronchioles

Alveolar ducts

Alveolar sacs

What does the splanchnopleuric mesoderm develop into?

Hemoplastic tissue

Blood cells

Blood vessel endothelium

Parts of the circulatory system

What does the somatopleuric mesoderm develop into?

Appendicular skeleton

Parietal division of the pleura, peritoneum, and outer pericardium

What parts of the appendicular skeleton come from the somatopleuric mesoderm?

Upper extremities

Scapula

Lower Extremities

Coxal (pelvic) bones

What forms the parietal divisions of the pleura, peritoneum, and pericardium (fibrous and parietal serous portions)?

Somatopleuric mesoderm

What is the term for the folding the the lateral plate mesoderm into two layers?

Lateral folding

Which parts of the trilaminar disc grow quickly in the caudal direction?

Mesoderm and ectoderm

Which part of the trilaminar disc grows slowly in the caudal direction?

Endoderm

What does unequal caudal growth speed of the layers of the trilaminar disc result in?

Folding

What direction does the trilaminar disc fold in caudally?

Sagittal axis

What is the pivot point of caudal folding?

Endoderm

Which gene is involved in rapid caudal elongation?

FGF-8

What inhibits the formation of somites in the caudal area?

FGF-8

T or F: Lateral growth of the ectoderm is rapid while lateral growth of the endoderm is slow

True

What causes coronal folding?

Different growth rates of the endoderm and ectoderm

What are the 4 parts of the trilaminar disc with no mesoderm?

Prechordal plate

Oropharyngeal membrane

Cloacal membrane

Notochord

What type of cells form the cariogenic area?

Epiblast cells

What is the third anterior migration wave?

Cardiogenic area

What forms the most primordial heart?

Cardiogenic area

What is the AKA of the cariogenic area?

Cardiogenic mesoderm

Cardiac crescent

First heart field

What are the great vessels?

Superior vena cava

Inferior vena cava

Pulmonary trunk

Ascending aorta

Pulmonary veins

What shape is the cardiogenic area?

Horseshoe

What do cells passing through the midstreak of the cardiogenic area become?

Ventricles

What do cells passing through the caudal region of the cariogenic area become?

Atria

What is the fourth migration wave?

Septum transversum

When does the fourth migration wave begin?

Week 4 (day 22)

What is formed by the septum transversum?

Liver

Diaphragm

What gene is highly expressed in the septum transversum?

BMP-4

What forms from segmentation of the paraxial mesoderm and cranial-caudal epithelialization?

Somites and somitomeres

What are the first 7 pairs of segments of the paraxial mesoderm called?

Somitomeres

What are pairs 8-23 of paraxial mesoderm segments called?

Somites