Term
| What are the four stages of development in the lungs? |
|
Definition
1. Pseudoglandula
2. Canalicular
3. Terminal Sac
4. Alveolar |
|
|
Term
Which stage of development (1st, 2nd, 3rd , 4th) is the pseudoglandular stage?
What occurs during this stage? |
|
Definition
The pseudoglandular stage is the 1st stage of lung development.
Tubular branching to terminal sac level
this occurs late in the embryonic period of development. |
|
|
Term
Which stage of development (1st, 2nd, 3rd , 4th) is the canalicular stage?
What occurs during this stage? |
|
Definition
The canalicular stage is the 2nd stage of lung development.
It involves the lung tissue becoming highly vascularised, the presentation of some terminal sacs.
It occurs early in the foetal period of development |
|
|
Term
Which stage of development (1st, 2nd, 3rd , 4th) is the terminal sac stage?
What occurs during this stage? |
|
Definition
The terminal sac stage is the 3rd stage of lung development.
The terminal sac formation continues and the lining of the sac thins.
Type 1 & 2 cells differentiate and surg=factant is produced. |
|
|
Term
Which stage of development (1st, 2nd, 3rd , 4th) is the alveolar stage?
What occurs during this stage? |
|
Definition
The alveolar is the 4th stage of lung development.
It involves the commencement of alveoli formation, with capillaries bulging into the lumen.
Surfactant production increases to a level sufficient to sustain life.
This stage occurs late in the foetal period & continues after birth. |
|
|
Term
| What makes up the respiratory fluid & where does it come from? |
|
Definition
-Respiratory tract glandular secretions
- Amniotic fluid - although most kept out by the larynx. |
|
|
Term
| What respiratory changes occur at birth? |
|
Definition
- Rapid decrease inO2, increase in CO2 stimulates breathing
- Bronchial tree & alveoli expand - this is maintained by surfactant.
- Lung expansion -> pulmonary vasodilation -> decreased resistance b=to blood flow within the lungs.
- Ductus arteriosus constricts. |
|
|
Term
| How is fluid removed from the lungs at birth? |
|
Definition
- Flows out into pharynx & mouth
- Evapouration into respired air
- Absorption into pulmonary lymphatics |
|
|
Term
| What do the pleuropericardial membranes originate from? |
|
Definition
| Folds of somatic mesoderm on the lateral body walls |
|
|
Term
| How is the pericardial sac formed? |
|
Definition
| by an ongoing expansion of the ventral margin of the lungs -> the pleuropericardial membranes divide the IEC between the pericardial cavity and pleural cavity to form the pericardial sac. |
|
|
Term
| What structures is the primitive diaphragm derived from? |
|
Definition
- Septum transversum
- Pleuroperitoneal membranes
- Dorsal mesentry
- Somitic cells from caudal cervical somites. |
|
|
Term
| What structures is the definitive diaphragm dervived from? |
|
Definition
- Muscular component - pleuroperitoneal folds, body wall
- Tendinous component - Spetum Transversum |
|
|
Term
| In the formation of the simple gut, what structure is the lumen derived from? |
|
Definition
| The cavity of the yolk sac - part of this cavity is incorportated into teh folding of teh embryonic disc as it folds. |
|
|
Term
| What cells are the layers of the simple gut tube made up of? |
|
Definition
Epithelial lining = endoderm
The remainder of the wall = splanchnic mesoderm |
|
|
Term
| How is the simple gut tube attached early in development? |
|
Definition
- Dorsal mesentry - persists as mesentries in adult\
- Ventral mesentry - mostly degenerates. some remnants remain. |
|
|
Term
| Which structures in the adult animal are derived from the early gut tube attachment - the ventral mesentry? |
|
Definition
1. Lesser omentum
2. Falciform ligament
3. Median ligament of bladder |
|
|
Term
| Which structures are dervived from the embryonic foregut? |
|
Definition
1. Pharynx & related structures
2. LRT
3. Oesophagus
4. Stomach
5. Proximal duodenum
6. Liver & biliary system
7. Pancreas |
|
|
Term
| Which structures are dervived from the embryonic midgut? |
|
Definition
1. distal duodenum
2. Jejunum
3. Ileum
4. caecum
5. Proximal colon |
|
|
Term
| Which structures are dervived from the embryonic hindgut? |
|
Definition
1. Distal colon
2. rectum
3. anal canal
4. Urinary bladder
5. Urachus (not in adult)
6. Most of urethra |
|
|
Term
| How does the stomach first appear as it starts to develop? |
|
Definition
- Dilation of gut tube, cranial to the septum transversum.
- It moves caudally as the lungs expand and oesophagus elongates.
- The greater curvature is positioned dorsally |
|
|
Term
| During the embryonic period the stomach rotates - which direction? |
|
Definition
- The stomach rotates ~90 degrees around its longitudinal axis.
- The greater curvature rotates towards the left side.
- During this period the ruminant stomach compartments form. |
|
|
Term
| During the foetal period the stomach rotates - which direction? |
|
Definition
The stomach makes its second rotation ~90degrees around a dorsoventral axis through the body.
The distal end of the stomach is carried from CD to right side of body and cranially.
(counter-clockwise when viewed from dorsally. |
|
|
Term
| How does the hepatic diverticulum form? |
|
Definition
| It grows out from the foregut into the ventral mesentry, toward the septum transversum |
|
|
Term
| What diverticula form from the hepatic diverticulum? |
|
Definition
1. Ventral pancreatic diverticulum
2. Cystic diverticulum -> gall bladder |
|
|
Term
| What is the origin of the dorsal pancreatic diverticulum? |
|
Definition
| It grows out from the foregut into the dorsal mesentry |
|
|
Term
| What cells is the primordial liver (hepatic diverticulum) composed of and what does it eventually form? |
|
Definition
- Endoderm - hepatocytes, bile canaliculi, hepatic ducts
- Splanchnic mesoderm - CT framework of liver |
|
|
Term
| How does the hepatic diverticulum expand? Which blood vessels does this involve? |
|
Definition
It engulfs the vitelline and then the umbilical veins. This forms the hepatic sinusoids.
The ductus venosus within the liver links the umbilical vein with the caudal vena cava |
|
|
Term
| What is the relationship between the primordial liver and the septum transversum? |
|
Definition
Primordial liver expands through ventral mesentry & contacts septum transversum
Liver surface remains adherent to diaphragm in adult |
|
|
Term
| Why does the foetus have a large liver? |
|
Definition
| It contains haemopoietic cell clusters, resonsible for RBC production. |
|
|
Term
| How is the pancreas formed? |
|
Definition
From 2 diverticula - ventral and dorsal.
the 2 diverticula fuse to create the pancreatic body & lobes. This occurs as the gut wall expands. |
|
|
Term
| What remnants of the pancreastic formation are obvious in the adult horse & dog? |
|
Definition
There are 2 pancreatic ducts, one from each of the primordial diverticula.
However, one regresses in pig, ruminants and cats. |
|
|
Term
| How do gut loops begin to form in the midgut? |
|
Definition
A U-shaped loop created when gut elongates faster than the body length.
This loop has a cranial & caudal limb.
The cranial mesenteric a. courses through the centre of the loop. |
|
|
Term
| How is the root of the mesentry formed? |
|
Definition
Associated with disproportionate elongation of limbs of the U-shaped mid-gut loop.
The limbs rotae around the primordium of the cr mesenteric a. |
|
|
Term
| What is the physiological herniation of the midgut? |
|
Definition
| The elongating midgut moves into the umbilical cord late in embryonic period, before returning to abdominal cavity. |
|
|
Term
| What is the urogenital septum? |
|
Definition
It is has a horizontal fold cranially and lateral ridges caudally.
These act to separate the anal and urogenital sinuses |
|
|
Term
| Describe the histiogenesis of the intestinal wall |
|
Definition
Temporary occlusionof gut lumen
Proliferation of endodermalcells→ occlusion
Occurs toward end of embryonic period of development
Vacuoles form shortly thereafter & fuse → recanalisation
Villiformation & cellular differentiation
Functional maturation of cell types |
|
|
Term
|
Definition
| The conceptus immediately after fertilization. A very large single cell. |
|
|
Term
| What are totipotent cells? |
|
Definition
| Cells of the blastomere up to the 8-cell stage. Capable of becoming any cell in the body |
|
|
Term
| Where does cleavage of the zygote occur? |
|
Definition
| Within the uterine tube, in the isthmus. |
|
|
Term
|
Definition
| A morula is a conceptus up to the 16-64 cell stage |
|
|
Term
| Define the term Blastocyst |
|
Definition
| The blastocyst is the morula once the blastocyst cavity forms (filled with fluid) |
|
|
Term
| What are the trophoblast cells? |
|
Definition
| single layer of cells on the periphery of the blastula. |
|
|
Term
| What is the role of the trophoblast cells? |
|
Definition
- Trophoblast cells are involved in absorption of nutrients from the uterus.
Later on they participate in formation of extra-embryonic membranes. |
|
|
Term
| What is the role of the zona pellucida surrounding the blastocyst? |
|
Definition
| Prevents adhesion of trophoblast cells to the endometrial lining. |
|
|
Term
| How does the bilaminar embryonic disc start to form? |
|
Definition
| The cells from the inner cell mass delineate -> form a layer lining the inside of the ICM & trophoblast = hypoblast. |
|
|
Term
| What does the hypoblast give rise to? |
|
Definition
|
|
Term
|
Definition
| Outer layer of cells on the bilaminar disc. They are continuous with the trophoblast layer of the edge of the disc. |
|
|
Term
| What are the three layers of the trilaminar embryonic disc? |
|
Definition
1. Ectoderm
2. Mesoderm
3. Endoderm |
|
|
Term
| Which structures arise from ectoderm? |
|
Definition
1. Epidermis of skin
2. Nervous system |
|
|
Term
| Which structures arise from endoderm? |
|
Definition
Epithelial lining of:
1. GIT
2. LRT
3. Bladder
4. Urethra |
|
|
Term
| Which structures arise from mesoderm? |
|
Definition
1. Bone & Muscle
2. CV system
3. Urogenital system
4. Serous membranes |
|
|
Term
| What is the primitive streak? |
|
Definition
An accumulation of epiblast cells forming 2 parallel ridges & a depression between them.
It is the centre of cellular proliferation |
|
|
Term
| What occurs during gastrulation? |
|
Definition
- Epiblast cells proliferate & form primitive streak.
- These cells then migrate into the:
1. Hypoblast layer -> "intraembryonic endoderm"
2. space btw the epiblast & hypoblast layers of
embryonic disc -> Intraembryonic mesoderm
- Mesodermal cells btw epiblast & hpoblast proliferate & migrate to create middle layer of cells btw trophoblast & hypoblast layers -> extraembryonic mesoderm
- Mesoderm splits into:
1. Somatic mesoderm
2. Splanchnic mesoderm |
|
|
Term
|
Definition
| Somatic mesoderm layer + ectoderm |
|
|
Term
|
Definition
| Splanchnic mesoderm layer + endoderm |
|
|
Term
| What is the septum transversum? |
|
Definition
| A thickened area of mesoderm at the cranial margin of the embryonic disc. Will become the diaphragm. |
|
|
Term
| Where does the vascular network first begin to form? |
|
Definition
| As cellular cords within the splanchnic mesoderm of embryonic disc & yolk sac |
|
|
Term
| How is the single heart tube formed? |
|
Definition
- Paired heart tubes form in splanchnic mesoderm craniolateral to oropharyngeal membrane.
- These fuse to create single heart tube, caudal to the stomadeum
- This creates a cardiac bulge.
- Themesoderm of heart tube then differentiates :
1. Inner lining - endothelial cells.
2. Outer layer - epimyocardial mantle secretes thick cardiac jelly, separates mantle from inner lining. |
|
|
Term
What are the vitelline vessels and how are they formed?
|
|
Definition
| The vitelline vessels are vessels within the yolk sac that develop from a vascular network in the wall of the yolk sac that fuses with the intra-embryonic vascular network. |
|
|
Term
| What are the components of the heart tube in the embryo? |
|
Definition
From venous to arterial end:
1. sinus venosus - right and left horns
2. Atrium
3. Ventricle
4. Bulbous cordis - tapers towards arterial end
5. Truncus arteriosus |
|
|
Term
| What occurs during bending of the heart tube? |
|
Definition
| - A U-shape then S-shape is formed -> alignment of primordial heart chambers |
|
|
Term
| What occurs during division of the artioventricular canal? |
|
Definition
- The endocardial cushions expand from the opposing walls of the opening and fuse.
- Primordia of the R & L AV openings are formed. |
|
|
Term
| What is the structure & function of the septum primum? |
|
Definition
| The septum primum is a thin, cresent-shaped fold that expands from the dorsal atrial wall toward the endocardial cushions. This is part of the partitioning of the atrium. |
|
|
Term
| What is the foramen primum? |
|
Definition
The foramen primum is a gap in the septum primum between the free edge of the septum primum fold and the endocardial cushions.
This foramen disappears when the fold fuses with the cushions. |
|
|
Term
| What is the foramen sceundum? |
|
Definition
| The foramen secundum is a spherical opening that forms in the septum primum before the foramen primum is obliterated. |
|
|
Term
| What is the septum secundum? |
|
Definition
| The septum secundum is a thick cresent shaped fold that forms parralell and to the right of the septum primum. |
|
|
Term
| What is the foramen ovale? |
|
Definition
The foramen ovale is a gap between the free edge of the septum secundum and the opposing atrial wall.
It persists throughout gestation.
This opening is slightly covered by the septum primum, which acts as a valve, permitting unidirectional blood flow from R -> L atrium only. |
|
|
Term
| What is the fate of the sinus venosus? |
|
Definition
The sinus venosus gets re-aligned with the enlarging R atrium.
Increased venous inflow via R horn of sinus venosus & decreased via left horn.
The right horn of the SV is incorporated into the sinus venarum of R atrial wall near vena caval openings.
The left horn of the SV is incorporated into the terminal section of the coronary sinus as it enters the R atrium |
|
|
Term
| How does the pulmonary vein become incorporated into the left atrium? |
|
Definition
The pulmonary vein grows as a single vessel outward from the left atrium as the lungs form.
The vessel branches distally towards the lung lobes.
Re modelling of the L atrium occurs & the pulmonary vein is incorporated into the L atrium as it expands. |
|
|
Term
| What does the primitive ventricle become? |
|
Definition
| The definitive Left ventricle |
|
|
Term
| What primordial structure does the definitive Right ventricle arise from? |
|
Definition
|
|
Term
| How is the ventricle partitioned? |
|
Definition
The interventricular spetum, a thick ridge, forms at the junction between the single ventricle and the bulbous cordis.
This ridge extends toward the fused endocardial cushions but does not contact them.
The gap between ridge & cushions is closed when the outflow tract of heart is divided by the conotruncal ridges. |
|
|
Term
| What occurs during partitioning of the outflow tract? |
|
Definition
The outflow tract (bulbous cordis and truncus arteriosus) is divided by spiral ridges.
These ridges form from opposing walls of the outflow tract, then expand and fuse.
This fushion creates the aorticopulmonary septum. |
|
|
Term
| How does the aorticopulmonary septum effect blood flow from the heart? |
|
Definition
| The aorticopulmonary septum divides the outflow tract so that blood will flow from the L ventricle into the aorta and blood from the R ventricle will go via the pulmonary trunk. |
|
|
Term
|
Definition
| The aortic sac is a bulge at the distal end ot the outflow tract of teh heart. The aortic arches arise from here. |
|
|
Term
| What are the dorsal aortae? |
|
Definition
They are paires (R & L) longitudinal vessels formed in splanchnic mesoderm of the embryonic disc.
They fuse caudal to the forelimb buds to form 1 aorta. |
|
|
Term
| How are the heart valves formed? |
|
Definition
The aortic & pulmonayr valves form as small outgrowths from the conotruncal ridges and the walls of the proximal truncus arteriosus.
The AV valves develop from the ventricular myocardium surrounding the AV canals. |
|
|
Term
| Where do the aortic arches arise from? |
|
Definition
| The ventral aortae extend cranially from the truncus arteriosus which is where the aortic arches arise, extending to the dorsal aortae. |
|
|
Term
| How many aortic arches are there? |
|
Definition
There are five pairs of vessles making up the aortic arches.
Arches are numbered 1st, 2nd, 3rd, 4th, 6th. |
|
|
Term
| What is the surface feature corresponding to each od the aortic arches? |
|
Definition
|
|
Term
What sequence do the aortic arches arise and also degenerate (or develop) in? |
|
Definition
|
|
Term
| What is the fate of the 1st and 2nd aortic arches? |
|
Definition
| The first and second arotic arches regress as the 3rd & 4th arches arise. May contribute to some minor vessels in the head. |
|
|
Term
| What is the fate of the 3rd aortic arches? |
|
Definition
The 3rd aortic arches become the common & internal carotid arteries.
Buds from these arches to form the external carotid arteries. |
|
|
Term
| What is the fate of the 4th aortic arches? |
|
Definition
The Left 4th aortic arch become the definitive aortic arch.
The right 4th aortic arch contributes to the R subclavian artery. |
|
|
Term
What is the fate of the 6th aortic arches? |
|
Definition
Buds from the 6th aortic arches become the pulmonary arteries.
Proximally the aortic arche scontribute to the pulomary trunk.
Distally - the left arch forms the ductus arteriosus, while the right arch regresses. |
|
|
Term
| What is the function of the ductus arteriosus? |
|
Definition
| To shunt blood from the pulmonary trunk to the aorta, so that it by-passes the lungs. |
|
|
Term
| Where do the vitelline arteries arise form? |
|
Definition
| The aorta at teh level of teh midgut. |
|
|
Term
| Where do the umbilical arteries arise from? |
|
Definition
| The caudal end of teh aorta. |
|
|
Term
| Which vessels are derivatives of the vitelline arteries? |
|
Definition
1. Coeliac artery
2. Cranial mesenteric artery
3. Caudal mesenteric artery |
|
|
Term
| What is the function of the vitelline arteries in the embryo? |
|
Definition
| The vitelline arteries recieve blood from the dorsal aorta and supply the yolk sac and therefore also supply the primitive gut with blood. |
|
|
Term
| What is the function of the umbilial arteries in the embryo? |
|
Definition
| The umbilical arteries recieve blood from the aorta and terminally brnch as the allantoic arteries. |
|
|
Term
| How is venous blood returned to the heart in an embryo? |
|
Definition
Via :
1. Paired cardinal veins - From cranial & caudla cardinal veins into the sinus venosus of the heart.
2. Paired vitelline veins - from yolk sac to sinus venossu of heart. |
|
|
Term
| What is the primordial structure that gives rise to the cranial vena cava? |
|
Definition
| The Right cranial cardinal vein. |
|
|
Term
| What is the fate of the vitelline veins? |
|
Definition
-Incorporated into the expanding liver as the hepatic sinusoids.
- Caudal to the developing liver they form an anastamoses around the gut loops - Some parts regress while the remainder becomes the hepatic portal vein.
- Cranial to the developing liver - The L vein degenerates, the R vitelline vein forms the caudal vena cava. |
|
|
Term
| Which structure gives rise to the caudal vena cava? |
|
Definition
| The Right vitelline vein, cranial to the developing liver. |
|
|
Term
| What is the function of the umbilical veins in the embryo? |
|
Definition
| They convey blood from the allantoic veins to the sinus venoss of the heart. |
|
|
Term
| What is the fate of the umbilical veins? |
|
Definition
- Incorporated into the expanding liver as the hepatic sinusoids (like the vitelline veins)
- Cranial to the dveeloping liver they regress.
- Caudal to the developing liver:
- R vein degenerates
- L vein enlarges - suuplies blood to ductus venosus in
liver, some blood enters liver parenchyma. |
|
|
Term
| What is the ductus venosus and what is it's function? |
|
Definition
The ductus venosus is a channel through the liver that links the L umbilical vein to the caudal vena cava (R vitelline vein)
This means most of the oxygenated blood returing from the placenta by-passes the hepatic sinusoids. |
|
|
Term
| When does the ductus venosus degenerate in each of the domestic species? |
|
Definition
- Pig & horse - DV degenerates during foetal period of development.
- Ruminants and carnivores - degenerates at parturition. |
|
|
Term
| Which structure in the neonate is a reminant of the umbilical vein? |
|
Definition
| The round ligament of the bladder. |
|
|
Term
| Which structure in the neonate is a reminant of the ductus venosus? |
|
Definition
| The ligamentum venosum within the liver. |
|
|
Term
| Where do Neural crest cells originate from? |
|
Definition
| The neural folds - they migrate to then contribute to the mesenchyme of head & neck, including skull, meninges, sclera, choroid & structures of the branchial arches. |
|
|
Term
Mesenchymal cells arise from one of two origins, what are these?
|
|
Definition
1. Mesoderm
2. Neurectoderm |
|
|
Term
| How does the musculature of teh head & neck form? |
|
Definition
| Cells of the somitomeres & cranial somites migrate into the developing head/neck (influenced by the neural crest cells) and then multiply & differentiate into skeletal muscle fibres. |
|
|
Term
| Which embryonic structure give rise to the meninges? |
|
Definition
| The neural crest cells surrounding the brain. |
|
|
Term
What are the three flexures that appear in the developing brain?
What order do they appear in? |
|
Definition
In order of appearance:
1. Midbrain flexure
2. Cervical flexure (at junction of SC & mylencephalon)
3. Pontine flexure. |
|
|
Term
What is the stomadeum? How is it formed?
|
|
Definition
A depression on the surface of the embryo, formed with the head folding of the embryonic disc.
The 1st branchial arches form the lateral wall of the stomadeum. |
|
|
Term
| Where are the branchial arches located? |
|
Definition
| Visible as transverse ridges ventrolaterally in the head/neck region. |
|
|
Term
| What are other names for the Visceral arches? |
|
Definition
- Branchial arches
- Pharyngeal arches. |
|
|
Term
| How many branchial arches develop in the embryo? How many are visible externally? |
|
Definition
| The 1st, 2nd, 3rd, 4th and 6th branchial arches but only 1st-4th visible externally. |
|
|
Term
| Which structures mark the separation between branchial arches both internally and externally? |
|
Definition
Internally - Pharyngeal pouches
Externally - Branchial grooves |
|
|
Term
| Which structures are contained within each branchial arch? |
|
Definition
- An aortic arch artery (1st, 2nd, 3rd, 4th or 6th)
- A cranial nerve (5th, 7th, 9th, 10th) |
|
|
Term
| Which structures are derived from the 1st branchial arch? |
|
Definition
- Jaws
- Muscles of mastication
- Pinna & auditory ossicle - some contribution |
|
|
Term
| Which nerve supplies the 1st branchial arch? |
|
Definition
|
|
Term
| Which structures are derived from the 2nd branchial arch? |
|
Definition
- Most of the hyoid apparatus
- Part of the pinna
- Part of auditory ossicles
- All of the muscles of facial expression |
|
|
Term
| Which nerve supplies the 2nd branchial arch? |
|
Definition
|
|
Term
Which structures are derived from the 3rd branchial arch?
|
|
Definition
- Part of hyoid apparatus
- Some pharyngeal muscles
- Some cartilages of larynx |
|
|
Term
| Which nerve supplies the 3rd branchial arch? |
|
Definition
|
|
Term
| Which structures are derived from the 4th & 6th branchial arches? |
|
Definition
| - Remainder of pharyngeal muscles & larynx, including intrinsic musculature. |
|
|
Term
| Which branchial arches are suppplied by Cranial Nerve X? |
|
Definition
|
|
Term
| Which embryonic structure is the external ear canal derived from? |
|
Definition
| The 1st branchial groove. |
|
|
Term
| What is the fate of the 2nd & 3rd branchial grooves? |
|
Definition
| They disappear when the 2nd branchial arch expands caudally & fuses with the surface of the ectoderm. |
|
|
Term
| What are the branchial membranes? |
|
Definition
| Thin tissue layers dividing the branchial grooves ffrom the pharyngeal pouches. |
|
|
Term
| Which structure gives rise to the tympanic membrane? |
|
Definition
| The 1st branchial membrane. This is the only branchial membrane that persists as a permanent structure. |
|
|
Term
| Which structure gives rise to the middle ear cavity and the auditory tube? |
|
Definition
|
|
Term
| What structures do the 3rd & 4th pharyngeal pouches give rise to? |
|
Definition
- Parathyroid glands
- Calcitonin-producing cells of the thyroid gland
- Thymus (excluding lymphocytes) |
|
|
Term
| How is the definitive tongue formed? |
|
Definition
- Derived from several swellings that arise from the floor of the caudal stomadeum & floor of pharynx.
- It is associated with the 1st-4th branchial arches.
- Sensory innervation from 5th, 7th, 9th & 10th cranial nerves
- Musculature derived from migrating somitic cells. |
|
|
Term
|
Definition
- Nasal placodes (circular thickenings of endoderm, surrounded by swelling of mesenchymal tissue = nasal processes.
- A nasal pit forms in the centre of each nasal process.
- Nasal processes fuse medially -> upper lip & primary palate.
- Maxillary processes expand & fuse with nasal processes. |
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Term
| What structure is the primary palate formed from? |
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Definition
| - The primary palate is derived from fusion of the medial portions of the nasal processes. |
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Term
| Which structure is the secondary palate derived from? |
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Definition
| The secondary palate is derived from internal folds extending medially from maxillary processes of 1st branchial arch. |
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Term
| Which structures are the pinna of the ear derived from? |
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Definition
| The mesenchymal proliferation in the 1st and 2nd branchial arches. |
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Term
| Which structures are the auditory ossicles derived from? |
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Definition
| The mesenchyme of 1st & 2nd branchial arches. |
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Term
| How is the inner ear formed? |
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Definition
| The inner ear is formed from the otic placode -> a depression from teh outer surface forming the otic vesicle -> membranous labyrinth of the ear. |
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Term
How is the retina of the eye formed? |
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Definition
| The retina is derived from an outpocketing of the forebrain vesicle that extends towards the surface ectoderm = the optic cup. |
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Term
| Which embryonic tissue is the lens of the eye derived from? |
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Definition
| The lens is formed from the lens vesicle -> derived from a thickening of ectoderm that becomes depressed from the surface. |
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Term
| How are the sclera and choroid of the eye formed? |
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Definition
| The sclera & choroid are derived from condensation of mesenchyme derived from neural crest cells. |
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