VBMS 213 Embryology Quiz 3
Terms
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ATRIAL DEVELOPMENT
5 STEPS -
PRIMARY SEPTUM (Septum Primum)
- grows ventrally from dorsal wall
- effaces the ventrally located PRIMARY FORAMEM (Ostium Primum)
- contains FENESTRATIONS
~~-- allows blood flow to continue
Fenestrations coalesce to form SECONDARY FORAMEN (Osteum Secundum)
- before Primary Septum reaches Endocardial Cushions and Primary Foremen is fully effaced
SECONDARY SEPTUM (Septum Secundum)
- grows ventrally from dorsal wall
- covers Secondary Foramen
- does not extend to Endocaridal Cushions
Dorsal portion of Primay Septum degenerates leaving ventral portion
FORAMEN OVALE
- is space between remaining flap of Primary Septum and its Secondary Foramen and the flap of the Secondary Septum - FUNCTION OF FORAMEN OVALE
-
Acts as a valve
Left Atrial pressure is lower than right because pulmonary circulation is restricted
Blood Flow:
- from Right Atrium
- through Foramen Ovale
- between Secondary and Primary Septums
- through Secondary Foramen
- into Left Atria
Foramen Ovale closes when:
- Pulomonary Circulation Opens
- Left Atrial pressure rises above Right Atrial pressure -
FORMATION
AORTA AND PULMONARY TRUNKS
6 STEPS -
Occurs via positioning of TRUNKUS ATRERIOSIS
Driven by Neural Crest Cells
- tf neural crest cells must migrate to heart
4 Swellings Develop
- RIGHT SUPERIOR TRUNCUS
- RIGHT DORSAL CONUS
- LEFT INFERIOUR TRUNKUS
- LEFT VENTRAL CONUS
Swellings are oriented at 90 deg to each other
Swellings grow so that the truncus meet the conus
- twisting occurs because of 90 deg orientation
AORTICOPULMONARY SEPTUM
- develops from the TWISTING of the swellings - TWO TWISTLESS TRAGEDIES
-
Aorta and Pulmonary Arteries may not seperate
Form two closed circulation systems
- Right Ventricle into systemic circulation
- Left Ventricle into pulmonary circulation
- Fatal Flaw - TETRALOGY OF FALLOT
-
Four abnormalities, occuring coincidentally, that results in insufficiently oxygenated blood pumped to the body
Ventricular Septal Defect
- opening between left and right ventricles
- generates other 3 defects
- usually results from Endocardial Cushion Defect
Displacement of Aorta over Ventricular Septal Defect
- aka Overiding Arota
causes
Narrowing of the Pulmonary Valve which results in
Thickening of Right Ventricle Wall
May have associated Patent Ductus Arteriosis
4% of Canine Heart Defects
6% of Feline Heart Defects
Most common heart defect in horses -
SEQULAE OF HYPOXIA
4 -
Lethargy
- a few weeks after birth when pups become active
Tachycardia
Poor Growth
Increased PVC
- polycytemia
- thicker blood -
VEINS
3 BIG ONES -
Vitelline
- drains yolk sac
Umbilical
- blood from placenta
- oxygenated and nutrient rich
Cardinal Veins
- drain embryo -
VEINS
DEVELOPMENT STORY -
Vasculature is Dynamic
- fetal and neonatal period
- many anastomeses
- degenerations
As LIVER enlarges is starts ot incorporate VITELLINE veins proximally
- forms LIVER SINUSOIDS
UMBILICAL vein regresses Proximally
- distal portion may be incorporated into LIVER SINUSOIDS
Left UMBILICAL VEIN enlarges
PORTAL VEIN develops from
- RIGHT Vitelline vein via
- distal anastomosies of VITELLINE veins
- atrophy of of LEFT Vitelline vein
- regession of Proximal Umbilical Veins
- drains gut and spleen
~~-- via mesenteric and splenic veins
DUCTUS VENOUSUS
- forms from shift of blood from Right to Left
~~-- enlargement of left Umbilical Vein
- no need to dextoxify
~~-- embryo not eating
~~-- detoxification by dam
- blood from Unbilical vein
~~-- bypasses most liver tissue
~~-- joins portal vein
~~-- drains to Vena Cava
- closes 3 - 5 days after birth
~~-- forms teres hepatis ligament -
PORTOSYSTEMIC SHUNT
TWO TYPES -
INTRAHEPATIC
- Ductus Venosus does not close
EXTRAHEPATIC
- External Bypasses form around liver
Normal liver functions not utilized
Idiopathic
- Intrahepatic may be due to lack of Aryl Hydrocarbon receptors required for closure
Genetics
- Autosomal variable expressivity
- purebred dogs 0.18%
- mixed breeds 0.05%
- cats higher prevalence golden or copper coloured iris
Presentation
- low growth
~~-- dont utilize nutrients from gut in liver
- lethargic
- Toxicity Problems
~~-- seizures are diagnostic if within 6 months of birth
- Jaundice - INTRAHEPATIC ATRERIOVENOUS FISTULA
-
Abnormal communication between hepatic artery and hepatic or portal vein
Fistula forms between artery and vein
- opening with NO CAPILLARY BED
- Tends to affect lobes or portions of lobes
- may have smaller liver due to lack of hepatic nutrition
Presentation
- similar to Portosystemic Shunt - HEPATIC MICROVASCULAR DYSPLASIA
-
Abnormal communication between hepatic ARTERIOLES and Hepatic or Portal VENULES
Affects whole lobes
Normal external appearance -
STATE THE
3 MAJOR CHANGES OF VASCULATURE -
Ductus Arteriosus closes to become Ligamentum Arteriosum
Oval Foramen closes to become Fossa Ovalis
Ductus Venosus closes to become Ligment Teres Hepatis
- note also encorporates Umbilical Vein - NEURULATION
-
Notochord signals overlying Ectoderm
- creates patch of NEUROECTODERM
Neuroectoderm forms CNS
- NEURAL GROOVE froms in neuroectoderm
- NEURAL FOLDS develop from enlarging Neural Groove
- cranial formation is first sign of brain development
Ectcoderm grows over top of Neural Folds
Neuroectoderm seperates from overlying Ectoderm
- NEURAL CREST forms alongside dorsal lateral edges of Neural Folds
~~ produces NUERAL CREST CELLS
Neural Folds come together forming NEURAL TUBE -
TWO FATES
OF
NEURAL CREST CELLS -
Form Ganglionic cells and supporting structures of PERIPHERAL NERVOUS SYSTEM
Become ECTOMESENCHYME
- migrated ventrally and Cranially
- surround pharynx and Proencephalon
- Impartanf for develoment of
~~ facial features
~~ facial skeleton
~~ facial Connective Tissue
~~ Aorticopulmonary Septum - NEURAL TUBE
-
Starts development in centre of embryo
Closure of Neural Folds proceeds in cranial and caudal directions from centre to from tube
Forms Brain Cranially and Spinal Cord Caudally
Carivty forms Ventricles and Spinal Canal - EARLY CNS DEVELOPMENT
-
Flexure and Rotation
Proencephalon
- Forebrain
~~ Telencephalon
~~-- Cerebrum
~~ Diencephalon
~~-- Thalamus Trio
Mesencephalon
- Midbrain
Rhombencephalon
- Hind Brain
~~ Metecehphalon
~~-- Cerebellum
~~-- Pons
~~ Myelencephalon
~~-- Medulla Oblaongata - CYCLOPIA
-
Single Medial Orbit with relatively normal rudimentary eye
Usually no vision
Various degrees of fusion of eyes
Eye development is relatively normal - HOLOPROSENCEPHALY
-
Failure of forebrain to divide and seperate
Results in Cyclopia
Cyclopathogenesis
- Diencephalon does not outpouch
- Mediated by defects in SHH (sonic hedge hodge) protein
~~ non utilization of cholesterol
~~ genetic chromosomal abnormality of SHH
~~ competition of plant toxins for cholesterol receptors
~~-- Jervine & Cyclopanine
~~--~~ Veratrum Californium aka Western False Hellebore
Normal Development
- cholesterol is important in signaling process for brain development
- Notochord induces cells to produce SHH
~~ directs development of forbrain and optic regions via mediation with cholesterol
- outpouching required for differentiation of telencephalon and diencephalon
Risk Period
- 14 Days Sheep, Goats and Cattle
Grieseofulvin
- only in Cats is linked to Cyclopia - HYDROCEPHALY
-
Alteration in Cerebral Spinal Fluid (CSF) dynmaics results in enlargement of Ventricles
Usually caused by obstruction causing improper drainage
- obstruction tends to be associated with abnormality other than ventricles
Mechanism
- Choroid Plexi continuously produce CSF
- fluid build up applies pressure to grey and white matter
~~ white matter is more affected
Presentation
- Depressed because cognition is reduced
- Domed Head
- vision deficits via ventricular pressure on optic nerves
- paralysis
- seizure
- aka Dummie Foals
~~ may not have domed head
Common in Dogs and Cats
- brachyocephalic and toy breeds
- Bermese Cats
- Siamese Cats
~~ autosomal recessive
Horses
- 3% of Births
Cows
- 4.5% especially Herefords
Congenital Hydrocephaly
- Treatmennt Futile
- Improper CNS development because most development is early -
HYDROCEPHALY
3 OBSRUCTIONS
3 AGENTS -
Spinal Bifida at level of spinal cord
Optic Nerve Hypoplasia at level of optic chiasm
~~ obstruction between lateral ventricles or in 3rd Ventricle
Cranial Facial Abnormalities
~~ blockage in ventricles
~~ especially Bermese Cats
Griseofulvin
Pavovirus
- Dog
Panleukopenia - SPINAL BIFIDA
-
Cleft in vertebral arch
- skeletal abnormality
- failure of Neural Tube to close
- dorsal spinal process is malformed in one or more vertebrae
- exposure or improper encasement of Spinal Chord
Defect is usually caudally oriented
- severity increases cranially -
SPINAL BIFIDA
TWO THERIES OF CAUSE -
Overgrowth of Neural Tube Cells prevents fusion of neural tube
Neural Tube fuses then later splits
Net result is skeletal abnormality -
SPINAL BIFIDA
THE THREE DEGRESS -
OCCULATA (Hidden)
- Defect is covered by skin
- External appearance is normal or may have pit on spine
- diagnose via radiagraph
- least severe
MENINGOCELE
- protrusion of spinal cord through vertebra
- nerve tissue remains encased in Dura Matter
~~ nerve tissue NOT exposed
- presents as bump on spine
~~ normal neural function unless trauma
MENENGOMYELOCELE
- Protrusion of Spinal Cord and membranes through defect
- neningies may or may not be intact
- skin broken by defect
- developing spinal cord damaged by exposure to proteins in Amniotic Fluid
- also physical damage
- most common
- most severe -
SPINAL BIFIDA
FOUR FACTORS -
Genetics
- English Bull Dogs
- Manx Cats
Sulphonamide
- decreased folic acid
Griesofulvin
- Cats
Methyl Mercury
- Cats - DERMOID SINUS
-
Neural Tube Defect
Incomplete seperation of Neural Tube from Overlying Ectoderm
Can occur anywhere from head to base of tail
Always on Midline
Small hole and tract
- large enough to allow infection
- particularly if drainage of CSF
Most commonly seen in Sacrococygeal Region
Mechanism
- Genitics and Folic Acid deficiency
- Rhodesiona Redge Back
~~ inverted hair stripe
- other dog breeds
- cats -
DERMOID SINUS
FIVE FABULOUS CLASSES -
III
- least pathalogic
- sinus extends into Connective Tissue only
- cyst
II
- sinus extends to Supraspinous Ligament
- ventral portion is closed fibrous strand
- may drain
I
- sinus extends to supraspinous ligament
- drains
IV
- sinus extends through Supraspinous Ligament and attaches to dura matter
- drains
V
- NOT OPEN TO SKIN
- sinus extends from muscle layer through to Supraspinous Ligament - MUSCULOSKELETAL SYSTEM
-
Paraxial Mesoderm produces Somites
- fused in head region
~~ ie SOMITOMERE
Somites produce 3 structures
- Dermatomes
~~ dorsal
~~ Dermis
- Myotome
~~ Muscle
- Sclerotome
~~ ventral
~~ migrates to fully enclose Notochord
~~ axial skeleton
~~ vertebral bodies
~~ caudal portion of one somite and cranial portion of adjacent somite form one veterbral body
~~ notchord becomes Nucleus Pulposis
- - MUSCLE
-
All skeletal muscle id derived from Myotome portion of Somites/Somitomeres
Myoblasts of Myotome fuse to form Multinucleate Muscle Cells
Dorsal portion of Myotome gives rise to Epaxial Muscles
- dorsal to Transverse Processes
Ventral portion of Myotomes give rise to Hypaxial muscles
- ie everything ventral to Transevers Processes
Muslsle Development requires
- Enervation
- Tension
~~ including Tendons
~~ stretched by growing bone
~~ tf abnormal bone = abnormal muscle
- most congenital muscle abnormalities are Secondary -
BONE
FIVE STEPS -
Most bones formed by Endochondral Osssification
Process
- Condenstation of Mesenchyme
- Differntiation of Chondroblasts
- Formation of Cartilage Model
- Cartilage Model Ossifies into Bone
- Structure of bone determined by
~~ Applied Forces
~~ Genetics
~~ tf Movement in Uterus critical
~~ most structural development takes place after birth - SKULL
-
Formed by 2 types of Ossification
Endochndrial
- Base of Cranium
INTRAMEMBRANOUS
- Flat Bones of Skull
- Facial Bones
Note
- Jaw has both types
- shape determined by cartilage model
Abnormalities
- normal development of skull involves interaction with many other structures of head
- eye
- brain - BLOCK VERTEBRAE
-
Error in RESEGEMENTAION of Somites
Partially seperated Vertebae
- may include vertebral disk malformations
Overlying vertebral body forms relatively normally -
MALFORMATIONS
OF
VERTEBRAL CORD
CLINICAL SIGNS -
Tend to compromise spinal cord via compression
Clinical Signs
- may occur at birth or later in life
- may have block vertebra that do not create clinical signs
- no compression = no clinical signs
Spinal Compression creates
- narrowing of spinal canal
- instability of involved segments
- animal is susceptabile to insults
~~ can be as minor trauma as a jump
- Luxation (aks dislocation)
- Fractures
Clinical Presentation
- Ataxia
- Paresis
- Paralysis -
HEMIVERTEBRA
PLUS 3 QUIZ FRIENDLY TERMS -
Common Cause for
- KYPHOSIS
~~ permenant FLEXION of spine
- LORDOSIS
~~ permenant EXTENSION of spine
- SCOLIOSIS
~~ permenant LATERAL DEVIATION
Wedge shaped vertebrae
- one or more
Defect in vasclar supply during develpment
~~ results in incomplete development
Abnormal Ossification
- may involve vascular deficiency
Normal in some dog breeds
- Screw Tails
~~ Bulldogs, Pugs extc
Manx Cats
Cats
- Hypervitaminosis A - ATLANTO AXIAL SUBLUXATION
-
Results from abnormal development of DENS
Dens normally origninates from C1
- later fuses with C2
Defects
- hypoplastic DENS most common
- absent DENS
- failure of DENS to fuse with C2
- improper development of muscles and Ligaments
Subluxation is usually Dorsal
- tf spinal cord problems
Toy breeds - MID CERVICAL SUBLUXATION
-
Horses
- malformation
- malarticulation
- especially C3-C4
- rapidly growing
- Thorough Breds
- aka wobblers
~~ ataxia
~~ paresis
Dogs
- C5, C6, C7
- rapid growth
~~ genetics
~~ nutrition
- Large breeds and Bassetts -
OCCIPITOATLANTOAXIAL MALFORMATION
SIX SEDITIONS -
Occipital Bone is Absent
Fusion of Atlas to Base of Skull
Wings of Atlas Reduced
Caudal Portion of Atlas ressembles Occipital Condyles
Dens is Hypoplastic
Axis has Transverse Processes which ressemble those of Altas
- ie wider
All Leison will be Present
- varying degrees
Produces reduced Foramen Magnum
- spinal compression
Caused by abnormal segmentation and development of Caudal Occipital and Cranial Cervical Sclerotomes
Clinical Signs
- Usually unable to get up
- if able to stand will have abnormal gait
- caudal palpation of abnormal wings
~~ Axis
Common in Arabs
- recessive
- also other breeds - OVINE HERIDITARY CHONDRODYSPLASIA
-
aka Spider Lamb Syndrome
Abnormal transformation of Cartilage to Bone
- defect of chonrocytes
- chondrocytes layed down in IRREGULAR PATTERN
- results in abnormal bone and bone growth during OSSIFICATION
- Abnormality may be in any part of skeleton
~~ mainly limbs and vertebrae
~~ may involve facial bones
Most common in Black Face Sheep
- 75% of occurance in Sufolk
- reduced in '60s (those were the days) to '80s via genetics
- avoid via genetic testing
Clinical Signs
- spayed legs
- kyphosis
- limb deviations
- age < 1 month - LIMB DEVELOPMENT
-
Initiates with development of Limb Field (bulge)
- bud stage once bud indentifiable
Ectoderm Thickens
- induces underlying mesoderm to from vascular Channel
~~ CRITICAL STEP
Apical Ridge of Bud induces underlying mesoderm to grow and differentiate
- Paddle stage
- elongation to Plate stage
- as limb nears final length
~~ Ventral Flexion
~~ Pronation
~~-- required for proper orientation of palmer/plantar surface - DIGIT DEVELOPMENT
-
Depends on Interdigital Necrotic Zones
- fusion or degeneration of digits occurs in species with less than 5 digits
- ie all originally develop 5 digits -
JOINT DEVELOPMENT
FIVE KEY EVENTS -
Movement Is Critical
- reduced or malformed joint
- abnormal development of tendons and ligaments
InterZone
- Perichondral layer of cells
- formed from Condenstation of mesochyme
Movement within INterzone leads to developmnent of Synovial Joint via
- cavitation
- production of Synovial Fluid
External portion of Interzone becomes Joint Capsule
Ligaments are formed from localized thickenings of Joint Capsule - AMELIA
-
Absence of one or more limbs
TBX5 Gene controls forelimbs
TBX4 Gene controls hindlimbs - ECTOPIC LIMB
-
Extra or Abnormaly placed Limb
Multiple expression of TBX gene - POLYDACTALY
-
Extra Digits
Excess interdigital necrosis
Genetic disposisiton
- Cats in Saskatoon - SYNDACTALY
-
Absence of Digits
Insufficient Interdigital Necrosis
Excess Fusion
Popular with Holsteins - HEMIMELIA
-
Missing a portion of a limb
Can result from crowded uterus
Twisted Kittens -
ARTHROGRYPOSIS
WHAT IS IT
FOUR WAYS TO HAVE IT -
Crooked Calf Syndrome
Contracted Limbs
- flexure most common
- also extension
Results from abnormal development
- usually displasia of muscle and tendons via
~~ Joint Defects Directly
~~ Improper Enervation to Muscle
~~ Muscle Defects Directly
~~ Insufficient Amniotic Fluid to allow proper Movement
Most Common in Cattle
- Horses
~~ Norwegian Fjiords
- Pigs
- Sheep
Multifactorial
- infections
~~ BVDV
~~ Bluetongue
- Genetics
~~ Austosomal Reccesive
~~-- Charlois
- Teratogens
~~lupines
~~ tobacco
~~ locoweed
~~ 40 -70 days cattle