Embryology Lecture 3-Week 3 thorugh 8 Flashcards
ECTODERMAL DERIVATIVES: Derivatives of Surface ectoderm:
- epidermis of the skin
- sweat, sebaceous, and mammary glands
- nails and hair
- tooth enamel
- lacrimal glands
- conjunctiva
- external auditory meatus
- oral and nasal epithelium
- anterior pituitary
- inner ear
- lens of eye
ECTODERMAL DERIVATIVES: Derivatives of Neural tube:
- central nervous system
- somatomotor neurons
- branchiomotor neurons
- presynaptic autonomic neurons
- retina/optic nerves -posterior pituitary
ECTODERMAL DERIVATIVES: Derivatives of Neural crest:
- bone, muscle, and connective tissue in the head and neck -peripheral sensory neurons
- postsynaptic autonomic neurons
- all ganglia
- adrenal medulla cells
- melanocytes
ECTODERMAL DERIVATIVES Derivatives of amnion:
-protective bag (with chorion around fetus)
MESODERMAL DERIVATIVES Derivatives of notochord:
- nucleus pulposus of an intervertebral disc
- induces neurulation
MESODERMAL DERIVATIVES: Derviatives of Paraxial columns (somites):
- skeletal muscle
- bone
- connective tissue (e.g. dorsal dermis, dura mater)
MESODERMAL DERIVATIVES: Derivatives of Intermediate mesoderm:
- gonads
- kidneys and ureters
- uterus and uterine tubes
- upper vagina -ductus deferens, epididymis, and related tubules -seminal vesicles and ejaculatory ducts
MESODERMAL DERIVATIVES: Derivatives of lateral plate mesoderm:
- Dermis (ventral)
- superficial fascia and related tissues (ventral)
- bones and connective tissues of limbs
- pleura and peritoneum
- GI tract connective tissue stroma
MESODERMAL DERIVATIVES: Derivatives of cardiogenic mesoderm:
- heart
- pericardium
ENDODERMAL DERIVATIVES: Derivatives of gut tube endoderm:
- GI tract (enterocytes)
- mucosal glans of GI tract
- parenchyma of GI organs (liver, pancreas)
- airway lining (larynx, trachea, bronchial tree)
- thyroid gland -tonsils
ENDODERMAL DERIVATIVES: Derivatives of Cloaca:
- rectum and anal canal
- bladder, urethra, and related glands
- vestibule
- lower vagina
ENDODERMAL DERIVATIVES: Derivatives of Pharyngeal pouches:
- auditory tube and middle ear epithelium
- palatine tonsil crypts
- thymus gland
- parathyroid gland
- C cells of the thyroid gland
ENDODERMAL DERIVATIVES: Derivatives of yolk sac:
- embryonic blood cell production (mesoderm)
- pressed into umbilical cord, then disappears
ENDODERMAL DERIVATIVES: Derivatives of allantois (from yolk sac, then cloaca)
- embryonic blood cell production (mesoderm)
- vestigial, fibrous urachus
- umbilical cord part disappears.
What is neurulation?
Process of differentiation of the neural plate to the neural tube.
Describe neurulation:
Process of differentiation of the neural plate to the neural tube. Neural plate forms as a result of induction by the notochord of its overlying ectoderm elevations = neural folds depression = neural groove The neural folds will approach each other, approximate and fuse ~25-28 days. This process forms the neural tube.
Describe the roll of neural crest cells and what is so notable about these cells during neurlation?
- During neurulation neural crest cells (cells at the crest of the neuroectoderm) disassociate.
- These cells undergo epithelial to mesenchymal transition (EMT) and migrate to the underlying mesoderm.
- Epithelial mesenschymal transition (EMT) is an important mechanism because mesenchymal cells are multipotent and can differentiate into a variety of cell types.
- epithelial cells lose their polarity and adhesion properties in favor of mobility and invasive properties of a mesenchymal cell
Neural crest cells undergo epithelial to mesenchymal transition and then migrate to the _________.
Neural crest cells undergo epithelial to mesenchymal transition and then migrate to the mesoderm.
Neural crest cells from the trunk region of the neural crest migrate after neural tube closure in three ways:
1.) Dorsally
- enter the ectoderm
- differentiate into melanocytes, skin and hair
2.) Ventrally
- through the somites
- differentiate into sensory ganglia, sympathetic and enteric neurons, Schwann’s cells, cells of the adrenal medulla.
3.) Cranially
•differentiate into craniofacial skeleton, neurons of the cranial ganglia, glial cells and melanocytes.
Mesodermal layer cell differentiation occurs beginning about the mid-3rd week based on _____.
Mesodermal layer cell differentiation occurs beginning about the mid-3rd week based on area (location).
The paraxial mesoderm organizes into segments termed _________ appearing cephalocaudally. Cells populate the ________ in a concenric whorl pattern.
The paraxial mesoderm organizes into segments termed somitomeres appearing cephalocaudally. Cells populate the somitomeres in a concenric whorl pattern.
In the head, somitomeres form in association with the segmentation of the neural plate and contribute to the ______________ of the head.
In the head, somitomeres form in association with the segmentation of the neural plate and contribute to the mesenchyme of the head.
Somitomeres organize into somites eventually forming
- 4 ______ (1 will disintegrate)
- 8 ______
- 12 ______
- 5 ______
- 5 ______
- 8-10 ______ (5-7 will disintegrate)
Somitomeres organize into somites eventually forming
- 4 occipital (1 will disintegrate)
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 8-10 coccygeal (5-7 will disintegrate)
Cells of the somites undergo _________ ________ ________ and surround the neuraltube and notochord
These cells differentiate into __________, which go on to become vertebrae and ribs.
Cells of the somites undergo epithelial mesenchymal transition and surround the neuraltube and notochord.
These cells differentiate into sclerotome, which go on to become vertebrae and ribs.
Intermediate Mesoderm differentiates into ________ structures.
Intermediate Mesoderm differentiates into urogenital structures.
Lateral Plate Mesoderm splits into two layers:
- ) Parietal layer
- ) Splanchnic layer
The space between the parietal and splanchnic layers becomes the _____ _____.
The space between the parietal and splanchnic layers becomes the abdominal cavity.
Describe the Parietal Layer (Somatic):
- ) Mesoderm with overlying ectoderm form the ____ ____ ____ ____.
- ) Forms the:
- ) Scerotome and muscle cells migrate into this layer and form:
- ) Cells give rise to ________ and _______ membranes which line the peritoneal, pleural and pericardial cavities.
Describe the Parietal Layer (Somatic):
- ) Mesoderm with overlying ectoderm form the lateral body wall folds.
- ) Forms the: dermis of the skin in the body walls and limbs, bone and connective tissue of limbs and the midline sternum.
- ) Sclerotome and muscle cells migrate into this layer and form: the costal cartilage, limb muscles, and the body wall musculature.
- ) Cells give rise to mesothelial and serous membranes which line the peritoneal, pleural and pericardial cavities.
Describe the Splanchnic Layer:
- ) Together with endodermal layer forms the wall of the ___ ____.
- ) Cells form a thin _____ ______ around each organ.
Describe the Splanchnic Layer:
- ) Together with endodermal layer forms the wall of the gut tube.
- ) Cells form a thin serous membrane around each organ.
Blood and cells and vessels arise from the:
Blood cells and vessels arise from the mesodermal layer.
Vasculature forms by __________ and __________.
Vasculature forms by vasculogenesis and angiogenesis.
Define vasculogenesis.
Assembly of cell precursors (mesenchymal derivate termed angioblast).
What is angiogenesis?
Forming vasculature by budding from existing vessels.
What role do blood islands play in the formation of blood and vessels?
-Blood islands appear in the beginning of week 3 and
progress through regions over time.
-They arise from clustering of angioblast cells to
form hemangioblasts (a common precursor for vessel and blood cell formation)
-Angioblasts go onto flatten and surround
the blood islands, forming endothelium
-The blood cells observed initially are later
replaced by hematopoietic stem
cells
What is the major derivate of the endodermal layer?
The GI tract
The GI tract or tube can be subdivided into 3 regions:
- ) Foregut
- ) Mid gut
- ) Hindgut
Describe the foregut.
- Bounded by the oropharyngeal membrane
which further develops into the oral
cavity.
•At week 4 the oropharyngeal membrane
ruptures establishes the connection
between the oral cavity and the
gut
Describe the Midgut.
Maintains continued communication with the yolk sac via the yolk sac duct.
Describe the Hindgut.
At week 7 the cloacal membrane ruptures establishing the distal opening of the gut tube, the anus.
In addition to the GI tract, the endoderm also gives rise to:
- Lining of the respiratory tract
- Tissues of the thyroid, parathyroid, liver and pancreas
- Supportive tissue of the tonsils and thymus
- Lining of the urinary bladder and urethra
- Lining of tympanic cavity and auditory tube
- Body Folding is the change from flat
disc to _____ shape.
- It occurs in _____ and
_____ planes.
- It occurs because…
- Head to tail folding occurs simultaneously
- As a result the cranial and caudal ends move _______ as the embryo elongates
- Body Folding is the change from flat disc to cylinder shape.
- It occurs in median and horizontal planes.
- It occurs because the growth of the disc fails to keep pace with the rate of growth along the long axis of the embryo.
- Head to tail folding occurs simultaneously
- As a result the cranial and caudal ends move ventrally as the embryo elongates
Head folding is caused by what?
Head folding is caused by the development of the brain.
•Brain expansion trajectory changes from dorsally toward the amniotic cavity to cranially growing beyond the oropharyngeal membrane and eventually overhanging the heart
Tail folding is caused by what?
Tail folding is caused by growth of the distal neural tube.
- The caudal eminence projects over the cloacal membrane.
- After folding the primitive streak lies caudal to the cloacal membrane.
- The connecting stock will now lie on the ventral side of the embryo.
In lateral folding, as teh two lateral walls form from the ______ ______ ______ (parietal layer) they move ventrally closing the body wall.
- As a result of folding, the amnion is pulled with the folds resulting in the embryo lying within the amniotic cavity.
- The ventral body wall closes completely except for the _____ _____ and _____ _____ located in the umbilical region.
- As the two lateral walls form from the lateral plate mesoderm (parietal layer) they move ventrally closing the body wall.
- As a result of folding, the amnion is pulled with the folds resulting in the embryo lying within the amniotic cavity.
- The ventral body wall closes completely except for the connecting stock and yolk sac located in the umbilical region.
•The primitive body cavity is created between two layers:
- ) ?
- ) ?
•When lateral folding is occurring, the endoderm also folds ventrally, closing to form the gut tube.
•The primitive body cavity is created between two layers
- ) Lateral plate medosderm (parietal layer)
- ) Lateral plate mesoderm (splanchnic).
•When lateral folding is occurring the endoderm also folds ventrally, closing to form the gut tube.
What is the parietal serous membrane?
•Lines the peritoneal pleural and pericardial cavities
What is the Splanchinic (visceral) Membrane?
Covers the abdominal organs, lungs, and heart.
_________ __________ covers the abdominal organs, lungs, and heart.
The splanchnic membrane covers the abdominal organs, lungs and heart.
In the formation of body cavities, what is the role of the dorsal mesentery?
- Acts to suspends the gut tube from the posterior body wall extending from the foregut to the hindgut.
- Its counter part the ventral mesentery only exists in the foregut.
What is the Septum Transversum? Where is it? What does it do?
- A block of mesenchyme that forms from the sphlanchnic layer
- This structure occupies the space between the thoracic cavity and the stalk of the yolk sac.
- It separates the thoracic and abdominal cavities leaving openings termed pleuroperitoneal openings
- This structure is double layers to allow for blood vessels, nerves and lymphatics to reach these organs.
The Septum Transversum goes on to form:
- The connective tissue of the liver
- Central tendon of the diaphragm
Name the embryonic body cavities.
- ) Pericardial
- ) Two pericardioperitoneal
- ) Peritoneal
In the formation of body cavities, the pleuropericardial folds grow in laterally, separating _____ and ______ cavities.
In the formation of body cavities, the pleuropericardial folds grow in laterally, separating pleural and pericardial cavities.
The diaphragm is formed from:
- Septum traversum (central tendon)
- Two pleuroperitoneal membranes
- Muscular somites of the cervical region
- Mesentary of the esophagus
