Anatomy 3 Flashcards
What does neurulation mean
- this refers to the formation and closure of the neural tube
describe how neurulation happens
- the notochord induces the overlying ectoderm to thicken and differentiate into the neuroectoderm and form the neural plate
- the neural plate then folds dorsally to give rise to the neural groove which then becomes the neural tube
- the converging edges of the neuroectoderm become the neural crest cells
- the neural tube is open at both ends at the anterior and posterior neuropores
- the anterior neuropore closes days 25-26 whereas the posterior neuropore closes days 27-28
- the neural crest cells then form a column of cells along both sides of the neural tubes
- they differentiate into peripheral nerves, endocrine glands, connective tissues and other specialised tissues
- the rostral cephalic part of the neural tube becomes the adult brain
- the casual part becomes the adult spinal cord
- The lumen of the neural tube gives rise to the ventricular system of the brain and central canal of the spinal cord.
what does the notochord eventually become
The notochord forms the nucleus pulposus of the intervertebral disk in adult
what do the anterior and posterior neuropores do
The anterior and posterior neuropores connect the lumen of the neural tube with the amniotic cavity.
when does the anterior and posterior neuropore close
- the anterior neuropore closes days 25-26 whereas the posterior neuropore closes days 27-28
what does the rostral cephalic part of the neural tube become
adult brain
what does the caudal part of the neural tube become
spinal cord
What does the lumen of the neural tube give rise to
- it gives rise to the ventricular system of the brain and central canal of the spinal cord
what do cranial neural crest cells develop into
- bones of the neurocranisum
- meningitis
- connective tissue
- several components of cranial nerves = these cells enter the pharyngeal arches and pouches to give rise to thyme cells
what do the trunk region of neural crest cells differentiate into
1) Pigment producing melanocytes that travel through the dermis into the ectoderm to colonize skin and hair follicles.
2) Migrate to each sclerotome (differentiated mesoderm) to form the dorsal root ganglia, sympathetic neurons, parasympathetic nerves, adrenomedullary cells, and Schwann cells of the gut, abdomen and pelvis.
what is the most common neural tube defect
spina bifida
what are the two types of spina bifida
- spina bifida cystic
- spina bifida occulta
Name two examples of spinal bifida cystica
Myelominingeocele
meningocele
describe a myelomeningocele
- most serious form of spina bifida cystica
- sac containing both CSF and nerves and parts of the spinal cord
describe a meningocele
- sac containing CSF and meninges only
- less common and usually not less severe
what is a spina bifida occulta
- most common dn mildest form
- one or more vertebrae have malformed
- can present with a small tuft of hair or dimple or birth mark
what happens if the anterior neuropore does not close
lead to cranial neural tube defects
give two examples of a cranial neural tube defect
- encephalocoele
- anencephaly
What is anencephaly
- when the baby is born without parts of the brain and skull
- cerebrum fails to develop normally
when can ancencepahly be detected
- 11-14 weeks using ultrasound (this is the time of skull ossification)
- use of maternal serum alpha fetoprotein - during pregnancy a small amount of AFP crosses the placenta and enters the meters blood stream but a high amount can indicate that the foetus has an open neural tube defect
what is maternal serum alpha fetoprotein made by
foetus and placenta
what is an encephalocele
- this is herniation of meninges and brain tissue outside the cranium usually in the midline
what does a canal meningocele contain compared to an encephalocele and ventriculocele
A cranial meningocele contains only meninges;
an encephalocele contains brain tissue;
a ventriculocele contains part of the ventricle within the herniated part of the brain.
what vitamin reduces the number of neural tube defects
- folate
what week to the 3 primary brain vesicles develop
week 4
what week do the 5 secondary brain vesicles develop
week 5
what are the three primary brain vesicles
= prosencephalon - forebrain
- mesencephalon - midbrain
- rhombencephalon - hindbrain
what are the 5 secondary brain vesicles
- telencephalon
- dinecepahlon
- mesencephalon
- metancephalon
- myelencephalon
describe what each of the secondary and primary brain vesicles develop into
prosencephalon forebrain = becomes telencephalon and diencephalon
- telencephalon becomes the cerebrum
- diencephalon becomes the thalamus, hypothalamus, pineal gland and retina
mesencpehalin midbrain becomes the mesencephalon
- mesencpehalin formed the midbrain
rhombencephalon the hind brain becomes the metencephalon, myelenecephalon
- mesencephalon becomes the pons and cerebellum
- myelencephalon becomes the brainstem and medulla oblongata
what is hydrocephalus
Hydrocephalus is dilatation of the cerebral ventricles
where is CSF produced
SF is mainly produced in the choroid plexus (found lining the ventricles)
how much CSF do we produce a day
500ml) of CSF per day but the brain can contain only about 120-150ml.
For this reason excess CSF is drained into the bloodstream via the arachnoid villi.
what can cause hydrocephalus
Hydrocephalus can be congenital or developed later in life (acquired) e.g. head injuries, stroke, tumours or meningitis
what is keying diagnosing hydrocephalus
CT and MRI
what is the treatment of hydrocephalus
- this is when shunts are implanted into the brain to divert the accumulated CSF
- Endoscopic third ventriculostomy - this is when a small hole is made in the floor of the ventricle to divert the flow of CSF - avoids the need for shunt if successful
What is cerebral palsy
t is a group of non-progressive neuro-muscular disorders caused by brain damage. It classified by severity, topographical distribution or motor function.
describe the different severities of cerebral palsy
Mild – means a child can move without assistance; his or her daily activities are not limited.
Moderate – means a child will need braces, medications, and adaptive technology to accomplish daily activities.
Severe – means a child will require a wheelchair and will have significant challenges in accomplishing daily activities.
what does quadriplegia mean
- all 4 limbs paralysed
what does diplegia mean
- legs more severely affected then arms
what does heiplegia mean
- one side of the body is affected
- arm is usually more involved than the leg
what does triplegia mean
- three limbs involved usually both arms and a leg
what does monoplegia mean
- one limb is affected usually an arm
what are the different types of motto neuromuscular dysfunction
- spastic
- dyskinetic
- athetoid
- ataxic
- mixed
describe what - spastic - dyskinetic - athetoid - ataxic - mixed mean
SPASTIC- tense, contracted muscles
ATAXIC- poor sense of balance, often causing falls
ATHETOID- includes cases with involuntary movement, especially in the arms, legs, and hands.
DYSTONIA- cases that affect the trunk muscles more than the limbs and results in fixed, twisted posture.
ATHETOID- constant, uncontrolled motion of limbs, heads and eyes
how is the diagnostic of cerebral palsy made
- observations of motor milestones
what can cause cerebral palsy
- vascular damage
- hypoxic-ischemia
- tetrogenic
- genetic
- infection
- toxins
- metabolic problems or trauma
what does the pharyngeal apparatus consist of
- pharyngeal arches, pouches, grooves and membranes
when does the pharyngeal apparatus develop
during week 4 of development
describe
- pharyngeal arches
- pharyngeal pouches
- pharyngeal grooves
- pharyngeal membranes
Pharyngeal arches (1-4 & 6) contain mesoderm and neural crest cells. In general, the mesoderm differentiates into muscles and arteries, whereas neural crest cells differentiate into bone and connective tissue. In addition, each pharyngeal arch has a cranial nerve associated with it.
Pharyngeal pouches are evaginations of endoderm that lines the foregut (e.g. oral cavity and oesophagus)- internal.
Pharyngeal grooves (clefts) are invaginations of ectoderm located between each pharyngeal arch – external.
Pharyngeal membranes are structures consisting of ecto-, meso- and endoderm and neural crest cells located between each pharyngeal arch.
what innervates
- pharyngeal arch 1
- pharyngeal arch 2
- pharyngeal arch 3
- pharyngeal arch 4
- pharyngeal arch 6
- pharyngeal arch 1 - CNV
- pharyngeal arch 2 - CNVII
- pharyngeal arch 3 - CNIX
- pharyngeal arch 4 - CN X(superior layrngeal nerve)
- pharyngeal arch 6 - CNX (Recurrent laryngeal nerve)
describe the adult derivates of
- pharyngeal arch 1
- pharyngeal arch 2
- pharyngeal arch 3
- pharyngeal arch 4
- pharyngeal arch 6
pharyngeal arch 1
Mesoderm: muscles of mastication, mylohyoid, anterior belly of digastric, tensor vali palatine, tensor tympani
Neural Crest: maxilla, mandible, incus, malleus, zygomatic bone, squamous temporal bone, palantine bone, vomer,
pharyngeal arch 2
Mesoderm: muscles of facial expression, posterior belly of digastric, stylohyoid, stapedius
Neural Crest: stapes, styloid process, lesser horn of hyoid
pharyngeal arch 3
Mesoderm: stylopharyngeus
Neural Crest: greater horn of hyoid
pharyngeal arch 4
Mesoderm: Muscles of soft palate, muscles of pharynx (expt stylopharyngeus), cricothyroid, cricopharyngeus, laryngeal cartilage
Neural Crest: none
pharyngeal arch 6
Mesoderm: intrinsic muscles of larynx (expt cricothyroid), upper muscles of oesophagus, laryngeal cartilages
Neural Crest: none
what is the adult deviate of
- Pouch 1
- pouch 2
- pouch 3
- pouch 4
- Pouch 1 = epithelial lining of auditory tube and middle ear cavity
- pouch 2 = epithelial lining of palatine tonsil
- pouch 3 = inferior parathyroid gland, thymus
- pouch 4 = superior parathyroid gland
what is the adult deviate of
- groove 1
- groove 2-4
- groove 1 = epithelial lining of external auditory meatus
- groove 2-4 = obliterated
what is the adult deviate of
- membrane 1
- membrane 2-4
- membrane 1 = tympanic membrane
- membrane 2-4 = obliterated
name the three middle ear bones
malleus
incus
stapes
What is a microtia
- this is a congenital deformity which is undeveloped or absent external ear
what can mcirotia cause
- this can cause conduction deafness which means that there is absent hearing due to lack of conduction through the ear canal
what do 20-40% of people with external ear defects have
20-40% of childrfen with external ear defects have additional defects asscoiated with the first pharyngeal arch, for example Pierre Robinson syndrome, and Treacher Collins syndrome.
describe how the thyroid gland develops
- In the midline of the floor of the pharynx (tongue), the endodermal lining of the foregut forms the thyroid diverticulum.
- The thyroid diverticulum migrates caudally (downwards), passing anteriorly to the hyoid bone and laryngeal cartilages.
- During this migration, the thyroid remains connected to the tongue by the thyroglossal duct, which later obliterates.
- The site of the thyroglossal duct is indicated in the adult by the foramen cecum of the tongue.
what is the tongue divided into
divded into anterior 2/3rd and posterior 1/3rd
what is the anterior 2/3 of the tongue formed by
The anterior 2/3rd is formed from pharyngeal arch one, which develops into a central tuberculum impar, and 2 lateral lingual swellings
what is the posterior 1/3 of the tongue formed by
Formed from pharynegal arch 2,3 and 4 which fuse to form the copula/hypobranchial eminence that develop in the floor of the pharynx.
what is the marker that separates the anterior 2/3 of the tongue and the posterior 1/3 of the tongue
The anterior and posterior parts then fuse leaving area of fusion between the anterior 2/3 and posterior 1/3 is indicated by the terminal sulcus.
what 3 swellings is the face formed by
The frontonasal prominence
The maxillary prominence (pharyngeal arch 1)
The mandibular prominence (pharyngeal arch 1)
describe how the face develops
- Bilateral ectodermal thickenings called nasal placodes develop on the ventrolateral aspects of the frontonasal prominence.
- The nasal placodes invaginate into the underlying mesoderm to form the nasal pits, thereby producing rides of tissue that from the medial nasal prominence and the lateral nasal prominence.
- A deep groove called the nasolacrimal groove forms between the maxillary prominence and the lateral nasal prominence and eventually forms the nasolacrimal duct and lacrimal sac
when does the inter maxillary segment form
Intermaxillary segment forms when the medial growth of the maxillary prominence pushes the two medial nasal prominences together at the midline.
what does the inter maxillary segment forms
The intermaxillary segment forms the philtrum of the lip, four incisor teeth and the primary palate
describe how the secondary palate forms
- The secondary palate forms from outgrowth of the maxillary prominences called the palatine shelves.
- Initially the palatine shelves project downward on either side of the tongue but later attain a horizontal position and fuse along the palatine raphe to form the secondary palate.
- The primary and secondary palate fuse at the incisive foramen to form the definite palate. Bone develops in both the primary and anterior part of the secondary palate.
- Bones does not form in the posterior secondary palate
when does cleft lip arise
This is failure of the maxillary prominence to fuse with the medial nasal prominence. The underlying mesoderm fails to expand resulting in a persistent labial groove. These can be bilateral or unilateral.
when does cleft palate rise
- Anterior - occurs when the palatine shelves fail to fuse with the primary palate.
- Posterior - occurs when the palatine shelves fail fuse with each other and with the nasal septum
- Anteroposterior - occurs when there is a combination of both.
what causes bifid nose/frontnasal dysplasia
- Incomplete fusion of the medial prominences
what causes oblique facial cleft
- Oblique facial cleft - fusion abnormality between lateral nasal process and maxilla.
what are the two parts of the skull
the neurocranium and viscerocranium
how many fontanelles are present at birth
6
what are the biggest fontanelles
the anterior and posterior are the biggest
what is the most important fontanelle
The anterior fontanelle is the most important one of these and the latest to ossify.
what does the heart develop from
The heart develops from areas in the mesoderm called the heart forming regions (HFR) near the cephalic end of the embryo. The HFRs form endocardial tubes either side of the notochordal groove.
what does the heart beat begin
day 22
what way does the heart fold
This folding occurs in a cephalo-caudal direction. Because of the longitudinal and lateral folding of the embryo the heart tubes move into the thorax and also brings the heart tubes together into a single tube.
what is a foramen ovale that remains open called
= patent foramen ovale
what is a well recognised feature of downs syndrome
tetralogy of fallot
what does the umbilical vein become after birth
- it is obliterated and replaced by a fibrous cord called the round ligament of the liver
what is the primitive gut tube formed of
The primitive gut tube is formed from the lateral, cranial and caudal folding of the trilaminar embryo
describe the difference between the midgut and foregut and hindgut
- the midgut remains attached ventrally to the yolk sac whereas the foregut and hindgut are blind ending
describe how the oesophagus forms
Formed by the division into the oesophagus dorsally and the trachea ventrally by the tracheoesophageal folds, which fuse to form the tracheoesophageal septum.
when does oesophageal atresia occur
Oesophageal atresia occurs when the tracheoesophageal septum deviates too far dorsally(favouring the trachea)
describe how the stomach forms
A fusiform dilatation forms in the foregut in week 4, which gives rise to the primitive stomach.
The primitive stomach rotates 90 degrees clockwise around its longitudinal axis.
what does the liver develop from
- the liver develops from an out pouching of the duodenum into the ventral mesentery called the hepatic diverticulum
what forms the gall bladder and ducts
Another diverituclum from the hepatic duct bud forms the gall bladder and ducts
where does the upper duodenum develop from
- develops from the casual portion of the foregut
what does the pancreas develop form
The pancreas develops from a larger dorsal divercticulum from the duodenum and a smaller ventral outpouching from the side of the common bile duct.
describe how the pancreas forms
The ventral pouch swings round posteriorly to fuse with the lower aspect of the dorsal diverticulum, trapping the superior mesenteric vessels between the two parts in the process.
The smaller segment takes over the main pancreatic flow leaving the original duct of the larger portion as the accessory duct.
What is the most cranial part of the midgut
Lower duodenum
describe how the midgut develops
The midgut enlarges rapidly during week 5 and becomes too large to be contained within the abdomen so forms a U-shaped loop (midgut loop) that herniates through the primitive umbilical ring beginning of week 6.
Simultaneously, the gut wall obliterates its lumen but is re-cannulated at the end of its development.
The apex of the herniated bowel is continuous with the vitello-intestinal duct and the yolk-sac. This connection is reduced to a fibrous strand, 98% of the time.
The axis of the loop is formed by the superior mesenteric vessels
The midgut loop consists of a cranial and a caudal limb.
The cranial limb forms the jejunum and upper part of the ileum.
The caudal limb forms the caecal diverticulum (later cecum and appendix). The rest of the caudal limb forms the lower part of the ileum, ascending colon and proximal 2/3 of the transverse colon.
The midgut loop rotates a total of 270 ⁰ counterclockwise as it returns to the abdominal cavity, thus reducing the physiological umbilical herniation around week 11.
The cephalic limb returns first and sits to the left, into the space left available by the bulky liver. The caudal end lies superficial to the cephalic limb with the caecum lying immediately below the liver.
The caecum then descends into its definitive position, in the right iliac fossa.
what is gastroschisis
- opening forms in the baby abdominal wall and therefore the gut pushes through this wall and the babies gut develops in the amniotic fluid
What is omphalocele
- an omphalocele is a birth defect in which an infants intestine or other abdominal organs are outside the body due to a whole in the belly button, covered in membranes
what is mockers diverticulum
Meckel’s Diverticulum represents the remains of the embryonic vitello-intestinal duct (connection between the primitive midgut and the yolk sac).
what is formed at the cranial end of the hindgut
Distal 1/3 of transverse Colon, descending Colon & sigmoid Colon
what is the terminal end of the hindgut like
The terminal end of the hindgut is an endoderm-lined pouch called the cloaca, which contacts the surface of the ectoderm of the proctodeum to form the cloacal membrane.
what is between the rectum and upper anal canal
The urorectal septum partitions the cloaca into the rectum and upper anal canal and the urogenital sinus.
what eventually fuses with the ectoderm
The urorectal septum eventually fuses with the ectoderm.
what are the 3 primitive neprogenci structures
pronephros, mesonephros and metanephros
describe the pronephros
Forms the pronephric tubules and pronephric duct. It is the most cranial nephric structure and regresses completely by week 5. Its distal part receives tubules of the next renal organ, the mesonephros.
describe mesonephros
Forms the mesonephric tubules and the mesonephric duct. It is the middle nephric structure and is a partially transitory structure. Most of the mesonephric tubules regress, but the Wolffian duct (mesonephric duct) persists and opens into the urogenital sinus.
describe metaphors
A diverticulum appears from the caudal end of the mesonephros duct which develops into the metanephric diverticulum/duct/ ureteric buds. A cap of tissue from the sacral intermediate mesoderm differentiates to form the metanephros which will later become the definitive kidney.
describe what regresses in the male embryological kidney
: the mesonephros persists and the paramesonephros regresses. The mesonephros duct forms the Wolffian duct which later becomes the vas deferens
what does the mesonephors form in males
- wolffain duct which becomes the vas deferns
what regresses in the female embryological kidney
the paramesonephros persists and the mesonephros regresses. The paramesonephros later forms the fallopian tubes, uterus and cervix.
what does the paramesonephros form
the fallopian tubes, uterus and cervix
describe how the collecting system develops
The ureteric bud is an outgrowth of the mesonephric duct on day 28
Once the ureteric buds forms a mass of tissue differentiates around the tip called the metanephric blastema.
The ureteric bud penetrates the blastema and then undergoes repeated branching to form the ureters, renal pelvis, major & minor calyces and collecting ducts. This occurs around day 32
The inductive influence of the collecting ducts causes the metanephric mesoderm to differentiate into metanephric vesicles, which later give rise to primitive S-shaped renal tubules that are critical to nephron formation.
The S-shaped renal tubules differentiate into the connecting tubules, distal convoluted tubule, loop of Henry, proximal convoluted tubule and Bowman’s Capsule.
Capillaries called glomeruli protrude into Bowman’s capsule
when is nephron formation fully developed
Nephron formation is completed at birth, but functional maturation of nephrons continues throughout infancy.
What develops from the ureteric bud
form the ureters, renal pelvis, major & minor calyces and collecting ducts.
what develops from the S-shaped renal tubules
The S-shaped renal tubules differentiate into the connecting tubules, distal convoluted tubule, loop of Henry, proximal convoluted tubule and Bowman’s Capsule.
Where is the fetal metanephros located
- the foetal metaphors is located at vertebrae level S1-S2
where are the adult kidneys located
he definitive adult kidney is located at vertebral level T12-L3.
why do the kidneys change location
The change in location results from a disproportionate growth of the embryo caudal to the metanephros.
How do the kidneys rotate
During the relative ascent, the kidneys rotate 90 degrees, causing the hilum, which initially faces ventrally, to finally face medially.
describe how the kidneys ascend
- arteries move upwards along with the kidneys
- arteries form during the ascent may persist and are called supernumerary arteries
where are the renal arteries
L2
what are supernumerary arteries
- arteries form during the ascent may persist and are called supernumerary arteries in renal ascent
- it is termed an aberrant renal artery if one of these supernumerary artery persists
what is an aberrant renal artery
- it is termed an aberrant renal artery if one of these supernumerary artery persists
what happens if the kidney fails to move upwards
persistent pelvic kidney
what happens if a two metanephric masses fuse at the caudal pole
- horseshoe kidney
where can a horseshoe kidney get stuck
- inferior mesenteric artery at L3
what is it called when there is a complete failure of kidney development
congenital absence of the kidney
what are polycystic kidneys
Occasionally, the metanephric tissue fail to link up with some of the metanephric duct collecting tubules. Blind ducts therefore form which subsequently become distended with fluid.
