Locomotion Flashcards
What aspect of the equine limb is most prone to injury?
Palmar aspect- subject to tremendous strain
What is the important difference in carpus between horse and dog stance?
Dog can overextend carpus and horse stands with straight carpus
What is the colloquial name of MCIII in equine forelimb?
Cannon bone
How many proximal sesamoid bones are there in equine forelimb?
2
What is the colloquial name for phalanx 1 in equine forelimb?
Long pastern
What is the colloquial name for phalanx 2 in equine forelimb?
Short pastern
What is the colloquial name for phalanx 3 in equine forelimb?
Coffin/pedal bone
What is the colloquial name for the distal sesamoid bone in equine forelimb?
Navicular
What is the colloquial name for the equine metacarpophalangeal joint?
Fetlock joint
What is the colloquial name for the equine proximal interphalangeal joint?
Pastern joint
What is the colloquial name for the equine distal interphalangeal joint?
Coffin joint
Which phalangeal joint has a capsule at the front?
DiPj (coffin joint)
List the collateral ligaments in the palmar aspect of the equine forelimb? (4)
MCPj collateral ligament, PiPj collateral ligament, DiPj collateral ligament, short collateral ligament of PSB
What is the function of collateral ligaments in palmar aspect of equine forelimb?
Keep movement in sagittal plane as much as possible
What is the function of the axial and abaxial palmar ligaments between P1 and 2 of equine forelimb?
Prevent overextension of palmar joint
What is the other name for interosseus in horse?
Suspensory ligament
Where does suspensory ligament of horse originate?
Proximally on palmar proximal MCIII
Where does suspensory ligament of horse insert?
Via proximal sesamoid bones
Where do the cruciate ligaments in the equine manus insert and originate?
proximal sesamoids and P1
where does the straight ligament insert and originate in the equine manus?
P1 to P2
where does the short ligament insert and originate in the equine manus?
proximal sesamoids to P1, deep to the cruciate ligament
where is the inter-sesamoidean ligament in the equine manus?
between the proximal sesamoid bones
What is the distal scutum?
Cartilage that protects collateral ligament of navicular
What is the navicular bursa?
Bubble of fluid between navicular bone and tendons
What is the distal attachment of the navicular to P3?
Impar ligament
where does the common digital extensor tendon insert in the equine?
P3
What is a method of management of navicular disease?
Palmar digital neurectomy severs nerves so horse can’t feel navicular pain anymore
What is the mechanical theory of navicular disease?
Damaged by repeated compression and grinds against P2
What is the vascular theory of navicular disease?
Navicular receives blood supply from many little meshes of arteries- may be compromised in disease
What is the role of the suspensory ligament in the stay mechanism?
Prevents overextension of MCPj?
What is the role of the palmar ligaments in equine stay mechanism?
Prevents overextension of PiPj
What is the role of the carpal check ligament to DDFT in the equine stay mechanism?
Prevents DiPj overextension- allows all weight to be transferred off muscle at times
What is the role of the radial check ligament to SDFT in the equine stay mechanism?
Prevents PiPj overextension- snaps tight when leg is at full extension, prevents muscle strain
What is the role of the fibrous old pronators in the equine elbow?
Act like additional collateral ligaments that resist intermediate position of elbow joint
What muscle slings the forelimb onto the trunk?
Serratus ventralis
What happens to serratus ventralis as species get larger?
Becomes more fibrous
What connects the biceps to extensor carpi radialis?
In horse
Lasertus fibrosus
What bones does lasertus fibrosus connect?
The scapula and the cannon bone
What does lasertus fibrosus prevent?
Flexion of shoulder
Where is the additional insertion of the suspensory ligament in the equine hindlimb?
Tarsal 4
What does the accessory ligament from the pelvis to proximal femur prevent?
Abduction
How does the equine stifle lock?
Medial patellar ligament hooks over medial trochlear ridge of femur, locks when pulled medially, unlocks when pulled laterally
how many tendons does the patella have?
3
How is extension of the hock linked to extension of the stifle?
SDF contains a fibrous band from the femur to tuber calcis on tarsus called peroneus tertius
what is peroneus tertius?
a fibrous band of SDF from the femur to the tuber calcis
What are hooves/claws/nails?
Epidermal outgrowths with a keratin sole and wall and a thickened skin pad
What protects the uterus and fetal membranes from the hoof?
The hoof slipper (perinychium)
What are the sensitive tissues of the hoof/claw?
Bone, hypodermis, dermis (corium) and epidermis
What is the insensitive tissue in the hoof?
Keratin horn that surrounds the sensitive tissue
How is horn produced?
Secreted by finger-like papillae around top of hoof wall and on sole, which point in direction horn grows
What is sole horn produced by?
Solar papillae
What is wall horn produced by?
Coronary papillae
What is the superficial shiny layer of wall horn produced by
Perioplic papillae (proximal)
Why are perioplic papillae a narrower band?
Produce thinner layer
How does wall horn migrate?
Secondary sensitive laminae crawl down primary sensitive laminae by repeatedly breaking and reforming desmosomes
What does the white line mark?
Where the sensitive/insensitive interface reaches the distal surface, the junction of the wall and sole
What are the 3 causes of laminitis mentioned?
Endocrine (obesity etc.), sepsis (lowers pH), continual pressure from supporting limb (e.g. lameness in other foot)
What in the hoof stores elastic potential energy when the horse bears weight?
The heel by splaying abaxially
What is the frog?
A hinge which allows the sole of hoof to widen
what is the Latin term for the frog of the hoof?
cuneus ungulae
What are the ungual cartilages in juvenile horses?
Hyaline cartilage
As the horse ages what do the ungual cartilages become?
Fibrocartilage, then ossify as side bones
What is the digital cushion?
A thickened wedge of hypodermis palmar to P2 and P3
What is the pedal pump theory?
The digital cushion is full of veins, so when compressed when foot lifted encourages venous return
What are the differences between the horse and donkey hoof?
Donkey hooves are more upright, more cylindrical than conical, more U than C shapes, shorter frog and the broken forward stance is a normal variant
What are the differences between the horse and ox hoof?
Ox sole and heel-bulb are both weight bearing, no digital cushion, thin hypodermis, thicker abaxial wall, lateral 4 bears more weight than medial 3, more extensive region of coronary papillae and no secondary laminae
What are the differences between the horse hoof and dog claw?
Dog has furred epidermis, and hairless epidermis in nail-bed, laminar dermis with thin epidermal coating on P3 and a large crumbly sole
What are the differences between the horse hoof and cat claw?
The cat has a huge P3 which is retracted passively by axial and abaxial dorsal elastic ligaments
How many pads do carnivores have in forelimb?
5 digital, 1 metacarpal, 1 carpal
How many pads do carnivores have in hindlimb?
4 digital, 1 metatarsal, 0 tarsal
What is the equivalent of a carpal pad in the ungulate?
Chestnut
what is the equivalent of a digital pad in the ungulate?
frog/bulb
What is the equivalent of a metapodial pad in the ungulate?
Ergot
What is the pelvis composed of?
Pelvic girdle, sacrum and first 3 vertebrae
What does the pelvic girdle comprise?
2 coxal (hip) bones which articulate ventrally at the pelvic symphysis
What is the pelvic symphysis?
An immovable joint between the 2 coxal bones that is cartilage in young animals and bone in adults
What 3 smaller bones form each coxal bone?
The ileum, the ischium and the pubis
What is the ileum?
The largest component of the coxal bone, forms wing of pelvis
What is the ischium?
The most caudal component of the coxal bone, forms caudal ventral pelvic floor
What is the pubis?
The smallest component of the coxal bone, forms cranial ventral pelvic floor
What is the acetabulum?
Where the femur articulates into the hip
What is the femur?
The largest of the long bones
What is the largest and most complex joint in the body?
The stifle
What is the overall motion of the stifle?
Overall works like a hinge
What 2 joints is the stifle composed of?
The femoropatellar joint and the femorotibial joint
What articulates at the femoropatellar joint?
Trochlea of femur and the patella
Which joint has the most extensive joint cavity?
Femoropatellar
What articulates at the femorotibial joint?
Femoral condyles, proximal tibial head and articular menisci
what produces the 2 synovial sacs in the stifle joint?
menisci
What is the patella?
Largest sesamoid bone in the body, articulates with femoral trochlea
What is the role of the patella?
Facilitates pull of quadriceps femoris over the stifle
How many patellar ligaments do carnivores, pigs and small ruminants have?
1
How many patellar ligaments do horses and oxen have?
3
Which is thinner the tibia or fibula?
The fibula
Which species have unfused tibias and fibulas?
Carnivores and pigs
What is the tibial tarsal bone called?
The talus
What is the medial bone of the proximal row of tarsal bones?
The talus (tibial)
What is the lateral bone of the proximal row of tarsal bones?
The calcaneus (fibular)
What is the fibular tarsal bone called?
Calcaneus
Which tarsal bone has a trochlea and why?
Talus, to articulate with tibia
which is the largest tarsal bone?
calcaneus
what is the lever for the Achilles tendon?
tuber calcis on calcaneus
What tendons make up the Achilles tendon?
Gastrocnemius, SDFT, biceps femoris, semitendonosus
Which tarsal joint has the greatest range of movement?
The tibiotarsal joint
What articulates at the tibiotarsal joint?
The trochlea of the tibial tarsal bone and distal tibia
What sort of joint is the tibio-tarsal joint?
Hinge joint
What sort of joint is the intertarsal joint?
A gliding joint with very little movement
Which species have all 7 tarsal bones?
Carnivores and pigs
Which tarsal bones are fused in horses?
1st and 2nd
Which tarsal bones are fused in oxen?
2nd and 3rd, 4th and central
Which limb bud forms first, forelimb or hindlimb?
Forelimb
What elements of the limb does the limb bud contain?
Precursors of skeletal elements (limb and limb girdle bones) and tendon sheaths
What elements of the limb migrate into the limb bud?
Muscles and blood vessels
What is the blade of the scapula formed from?
Dermomyotome
What mediates proximo-distal differentiation of the limb bud?
The apical ectodermal ridge releasing morphogens
What does progressively earlier ablation of the apical ectodermal ridge cause?
Loss of progressively more proximal elements: autopod= normal, zeugopod= late, stylopod= early
What generates the cranio-caudal orientation of the limb?
The zone of polarising activity lying caudally
What is the result of grafting a zone of polarising activity onto the cranial edge of a limb bud?
mirror image duplication
What is polydactyly?
Extra digits
What is syndactyly?
Fusion of digits
What is a common cause of polydactyly?
Ectopic medial expression of ZPA-related genes
What is the mechanism of bone formation in most of the trunk and limbs?
Endochondral ossification
What forms the model for cartilage?
Mesenchymal condensation
What does blastemal condensation form?
Large, tightly packed mesenchyme cells
what is chondrification?
when cells differentiate into chondrocytes
what is hypertrophy?
chondrocytes at the centre stop dividing and swell- this is interstitial growth. the connective tissue around the model is compressed into perichondrium, and the inner surface is chondrogenic
What happens in early mineralisation?
central chondroblasts start to mineralise matrix and perichondrial cells become osteoblasts forming a cylindrical cortical bone collar and compact bone is produced
What is vascular invasion?
Osteoblasts accompany vessels through cortical bone, osteoblasts lay down primary spongiosa (eventually forms cancellous bone)
What happens to further lengthen the diaphysis after vascular invasion?
Chondrocytes proliferate, more hypertrophy, marrow cavity enlarges
What causes the diaphysis to thicken at epiphysis end?
Traction on periosteum leaves thin discs of cartilage between epiphyses and diaphysis
What causes most pre and post-natal growth?
Growth plates
How many growth plates are in most long bones and vertebral centra?
2 (one at each end)
Which bones only have one growth plate?
Accessory carpal bone and fibular tarsal bone (calcaneus)
How do growth plates close?
They are bridged by bone and perforated by vessels
What are the layers of developing bone in growth plates?
Reserve cartilage (hyaline), proliferation (columns form), maturation (stop dividing and swell), hypertrophy and calcification, cartilage degeneration, osteoblast invasion, osteogenic zone
Which equine bones only have 1 growth plate remaining by birth?
MCIII, MTIII, P1 and P2
What types of growth plates are there?
In compression (proximal radius), in tension (proximal ulnar), flake epiphyses (iliac crest), evolutionary relics (scapula, pelvis)
What are particularly susceptible to angular limb deformity? (2)
Fast growing animals like giant breeds and fast growing bones like ulna, tibia
What is the longest bone in the dog?
The ulna
Where do joints form in development?
In pre-existing gaps between blastemal condensations
What muscles come from the ectoderm? (4)
Piloerector, mammary glands, iris, ciliary body (from neural crest)
What muscles come from the splanchnic mesoderm? (4)
Gut, bronchial, urinary smooth muscle, cardiac striated muscle
What muscles come from the myotome of the somitic mesoderm? (5)
Dorsal spinal muscles, ventral spinal muscles, body wall muscles, diaphragm muscle, limb muscles
What modern subclass of chordates probably swims similarly to pre-vertebrates?
Cephalochordates
How do cephalochordates swim?
Gel-like cellular notochord resists compression, is flexed laterally by segmental somitic muscles
Why did early tetrapods have fused vertebral elements?
Spine had to be very robust to resist torsional strain of footfalls
What are the spinal movements?
Sagittal plane flexion and extension, frontal plain flexion, axial rotation
What is the neural spine on a vertebra?
The dorsal spinous process
What are the spines that stick outwards on the vertebrae called?
Transverse processes
What is the hole in the vertebra called?
The vertebral canal
What does the nerve pass through in a vertebra?
The caudal vertebral notch
What do the vertebrae form from?
The sclerotome (medial part of somite)
what sort of development forms the vertebrae?
endochondral development
What are the regions of the spine?
Cervical, thoracic, lumbar, sacral, caudal
Where is the cervical region of the spine?
Cranial to ribs
Where is the thoracic region of the spine?
Articulating with the ribs
Where is the lumbar region of the spine?
Between the ribs and sacrum
Where is the sacrum?
Articulates with the pelvis at sacroiliac joint
Which regions of the spine are very mobile?
Cervical and caudal
Which region of the spine is responsible for frontal plane movement?
The thoracic region
Which region of the spine is responsible for sagittal plane movement?
The lumbar region
How many cervical vertebrae do all domestic species have?
7
Which mammals don’t have 7 cervical vertebrae?
Manatees and sloths
How many thoracic vertebrae do dogs, cats and ruminants have?
13
How many thoracic vertebrae do pigs have?
14/15
How many thoracic vertebrae do horses have?
18/19 (17 in Arabs)
how many thoracic vertebrae do rabbits have?
12/13
How many lumbar vertebrae do dogs and cats have?
7
How many lumbar vertebrae do ruminants have?
6
How many lumbar vertebrae do pigs have?
6/7
How many lumbar vertebrae do horses have?
6
How many lumbar vertebrae do rabbits have?
6/7
How many fused sacral vertebrae do dogs and cats have?
3
How many fused sacral vertebrae do ruminants have?
5
How many fused sacral vertebrae do pigs have?
4
How many fused sacral vertebrae do horses have?
5
How many fused sacral vertebrae do rabbits have?
3
What movement does the C1-skull joint produce?
Nodding
What movement does the C1-C2 joint produce?
Head shake
What sort of joint is the C1-skull joint?
Hinge
What sort of joint is the C1-C2 joint?
Pivot
What parts of C1 are incorporated into C2?
The centrum and neural spine
What is the C1 centrum in C2 called?
The dens or odontoid process
What is C1 called?
The atlas vertebra
What is C2 called?
The axis vertebra
In C1 where does the nerve exit from?
The lateral foramen
What are the characteristics of C3-C7?
Short neural spines, 2-pronged transverse processes
What is different about C6 to the other cervical vertebrae?
Large ventral laminae for longus colli muscle (flexor) to attach
Which cervical vertebra does the vertebral artery bypass?
C7
Where does the vertebral artery pass through in vertebrae?
The transverse foramina
What are the characteristics of the thoracic vertebrae?
Long neural spines and short transverse processes which articulate with ribs
What does the rib articulate with?
Transverse processes and centrum of thoracic vertebrae (capitulum)
What happens caudally to the thoracic vertebrae?
Blend into lumbar vertebrae
Which is the final thoracic vertebra with its neural spine pointing caudally?
Diaphragmatic vertebra
Which thoracic vertebra has a neural spine pointing cranially?
Anticlinal vertebra
What is a defining characteristic of the lumbar vertebrae?
Long transverse processes
Which way are the transverse processes of the lumbar vertebrae directed in large animals?
Laterally
Which way are the transverse processes of the lumbar vertebrae directed in small animals?
Ventro-cranio-laterally
Why do lumbar vertebrae have inter-transverse synovial articulation?
Region with lots of muscle mass so extra support (could also be for support when rearing for horses)
What is lost in the caudal vertebrae moving caudally?
Neural spines and arches, then minor, articular and transverse processes, until only centrum left
Why do carnivore Cd 4-7 vertebrae have haemal arches?
to protect the ventral caudal artery
Which joint is the site for epidural analgesia?
The S-Cd1 joint (first mobile joint after sacrum)
What are most intervertebral joints composed of?
2 planar synovial joints between articular facets, one unusual symphysis between centra (intervertebral disc)
What is the intervertebral disc made up of?
Cartilaginous cranial and caudal endplates fused with annulus fibrosus attached to nucleus pulposus by transitional zone
What gives the intervertebral disc its blood supply?
The endplates via diffusion
Where is the intervertebral disc thinnest?
on its dorsal end
What is the annulus fibrosus?
Develops from sclerotome, is interwoven collagen fibres running concentrically with a coating of proteoglycan to smooth movement of collagen fibres over each other and resist tension and torsion
What is the nucleus pulposus?
A vestige of the notochord, mostly proteoglycan so massive water content to give shock absorbing capacity and resist compression
Between which vertebrae is there no disc?
C1 and C2
Which vertebrae have no synovial joints
Caudal vertebrae
What is the difference in the overall spine in oxen and horses?
Straighter and less mobile, longer processes, interlocking facets
In which species is there still some movement at the lumbosacral joint?
Horses
Which ligament runs over the top of the spinal column?
The supraspinous ligament
Which ligaments run between the neural spines of vertebrae?
The interspinous ligaments
Which ligaments run from the ventral aspect of the caudal arterial process to the lamina?
Interarcuate ligament
Which ligament runs through the vertebral canal from dens to Cd1?
The dorsal longitudinal ligament
Which ligament runs between the transverse processes?
Intertransverse ligament
Which ligament runs along the bottom of the spinal column from T5 to S1
Ventral longitudinal ligament
Which ligament is between rib heads in thoracic region?
Intercapital ligament
What is the nuchal ligament?
Elastic extension of supraspinous ligament to cranial neck/head
Which species are the nuchal ligament quite extensive in?
Large, e.g. horse
Which species are the nuchal ligament absent in?
Pig and cat
What are the hypaxial flexor muscles that run along the top of the spine? (3)
Sternocephalicus, longus colli, sublumbar muscles
What does sternocephalicus flex?
The neck
What does longus colli flex?
The neck
What are the hypaxial flexor muscles that run ventrally? (2)
Scalenus and rectus abdominis
What are the epaxial extensor muscles?
Splenius, transversospinales, longissimus, iliocostalis
What region of the spine does transversospinales cover?
All of the spine
What region of the spine does longissimus cover?
Ilium to skull
What region of the spine does iliocostalis cover?
Ilium to first rib
What is the secondary function of sacrospinales?
Can flex in the frontal plane
What are the subdivisions of transversospinales? (6)
Spinales, semispinalis, multificius, rotatores, interspinales, intertransversarii
What extrinsic muscles does the tail have?
Sagittal flexor and extensor muscles: medial, lateral, dorsal and ventral sacrocaudalis
what are the intrinsic muscles in the tail?
continuation of transversospinales
What type of joint is the atlanto-occipital joint?
Concave-convex hinge, 2 synovial joints
What is the costo-vertebral joint?
2 synovial joints aligned to swing rib laterally, cranially, ventrally
What is the sacro-iliac joint?
A central synovial joint with very strong ligaments and some sagittal plane rotation
What is the cranial boundary of the abdominal cavity?
Diaphragm
What is the dorsal boundary of the abdominal cavity?
lumbar vertebrae and fascia
what is the caudal boundary of the abdominal cavity?
pelvis
what is the ventro-cranial border of the abdominal cavity?
the sternum
What is the lateral boundary of the abdominal cavity?
caudal ribs
What 3 muscles make up the lateral wall of the abdomen?
External abdominal oblique, internal abdominal oblique and transversus abdominis
Which direction do the fibres of EAO run?
Dorso-cranially to ventro-caudally
Which direction do the fibres of internal abdominal oblique run?
dorso-caudally to ventro-cranially
Which direction do the fibres of transversus abdominis run?
transverse direction
where does rectus abdominis run along?
the ventral midline
what direction do fibres of RA run?
cranio-caudal direction from rib 1 + sternum to prepubic tendon
what is the insertion of the abdominal muscles?
linea alba
where does the falciform ligament lie?
within the abdominal cavity ventrally
at the cranial end of the abdomen which muscles are deep to RA?
TA and IAO
in the middle of the abdomen which muscle(s) are deep to RA?
TA
At the caudal end of the abdomen which muscles are deep to RA?
None of them
What lines the abdominal cavity?
Parietal peritoneum
What covers abdominal organs?
Visceral peritoneum
Where does parietal peritoneum develop from?
lateral plate mesoderm
where does visceral peritoneum develop from?
splanchnic mesoderm
what do the peritoneal membranes produce?
peritoneal fluid to lubricate movement
what is the name of the potential space between the 2 peritoneal membranes?
peritoneal cavity
what is the role of the abdominal muscles?
supportive and movement (respiratory, sneezing, coughing, vomiting, defacation)
What are the differences in the equine abdomen?
Shorter, substantial aponeurosis, well developed tunica flavia, heave line (not normal to be visible), paralumbar fossa
What does the aorta split into caudally?
internal and external iliac arteries
How many epigastric arteries are there?
4 (caudal/cranial, deep/superficial)
What do the superficial epigastric arteries run deep to?
Tunica flavia
What do the deep epigastric arteries run inside?
Rectus sheath
What is the innervation of the abdomen?
Spinal nerves from spinal chord run in ventral branches from spinal cord
What is the femoral canal/ring?
Gap between insertion of EAO on ileum ring and concavity of ileum
What passes through the femoral canal/ring?
The femoral nerve
What forms the inguinal canal?
Progressive ends of muscles and a slit in EAO/thickening of fascia transversalis creates flat canal
What is the inguinal ligament?
Thickened caudal border of EAO
What structures pass through the inguinal canal?
Genitofemoral nerve, external pudendal artery and vein, caudal superficial epigastric artery and vein, in males spermatic cord and cremaster muscle
What does a female have between the deep and superficial inguinal ring?
Vaginal process
What is a hernia?
A breach of abdominal musculature
What is a dermatome?
A region of skin supplied by a single nerve
What direction is dorsal?
Towards the back
What direction is ventral?
Towards the belly
What direction is cranial?
Towards the front
What direction is caudal?
Towards the back end
What direction is rostral?
Towards the head
What direction is dorsal below the hock?
top of paw
What direction is palmar?
sole of paw
What direction is cephalic in embryos?
Towards the front end
What direction is caudal in embryos?
Towards the back end
What is axial?
Near the axis in limbs
What is abaxial?
Away from the axis in limbs
How are digits numbered?
From medial to lateral
What direction is distal?
Away from body
What direction is proximal?
Toward body
What are the aspects of the eyeball?
Anterior (front) and posterior (back)
What is a stylopod?
One big bone in limb
What is a zeugopod?
Two bones in limb
What is an autopod?
Less than or equal to 5 digits
What is evolution?
Change in animal species and speciation over time
What is natural selection?
The mechanism of evolution
What happens in natural selection?
Advantageous characteristics are propagated in later generations due to increased reproductive success
What is the only valid way of classifying animals?
Cladistics
What does a clade contain?
All the descendants of a single ancestral species
How are descendants of an ancestral species defined?
By having one or more shared, derived, novel characteristics inherited from ancestral species
What characteristics are used in cladistics?
Morphological or molecular characteristics
What is convergent evolution?
When animals evolve similarly without common ancestors as they fill similar niches
What are amniotes?
Species that can reproduce away from water
What are the criteria for domestication? (4)
Flexible diet, rapid growth, breed in captivity, good disposition
What is archaeological evidence for domestication? (5)
No local wild ancestors, skewed sex and age distribution, remains near settlements, husbandry-related tools, artistic representations
What is morphological evidence of domestication? (9)
Smaller, reduced weaponry (horns), shorter hair, smaller brain, neoteny, richer colours, shorter muzzle, fat deposits, smaller sense organs
What is neoteny?
Juvenile characteristics in adult
What are the 3 fundamental elements of development?
Pattern, specialisation, growth
What is the first stage of development after fertilisation?
Cleavage stages
What is the ball of cells formed in the cleavage stage called?
A morula
What is the first specialisation in embryo development?
Trophoblast and inner cell mass
What is the blastocoel?
Fluid filled cavity between the ICM and trophoblast
What does the trophoblast develop into?
Placental membranes
What is the blastocyst?
The embryo when the ICM, trophoblast and blastocoel are present
What does the ICM subdivide into?
Hypoblast and epiblast
Which layer of the ICM develops into the embryo?
Epiblast
What does the hypoblast develop into?
Extra embryonic membranes
What is the amniotic cavity?
A second fluid-filled cavity formed between the epiblast and trophoblast
What 2 pieces of evidence prove that instructions for the definitive body aren’t present before gastrulation?
- Early embryos can be split and as long as both parts contain some ICM will each form perfectly formed animal (monozygotic twins)
- Can remove cells or transplant cells between blastocysts- produces chimera of cells from transplanted and recipient blastocysts
What is acquired in gastrulation?
A body axis with a head and tail; inside out specialisation with 3 basic germ layers; left-right axis
What are the 3 germ layers formed in gastrulation?
Endoderm, mesoderm, ectoderm
Where is gastrulation initiated?
In primitive streak
What is the inner germ layer?
Endoderm
What is the middle germ layer?
Mesoderm
What is the outer germ layer?
Ectoderm
What is the central end of the primitive streak called?
The primitive pit/Hensen’s node
What determines which germ layer epiblast cells become?
Proximity to trophoblast
What determines whether cells will be cranial or caudal?
Proximity to Hensen’s node: closer=cranial
What do ectoderm cells develop into? (3)
CNS, PNS, epidermis
What do mesoderm cells develop into? (8)
Muscles, bones, kidneys, reproductive system, blood, vascular system, peritoneal linings, dermis
What do endoderm cells develop into? (6)
Lining of intestines and associated organs (liver+pancreas), lining of lungs and respiratory tract, thymus, parathyroid
What are the subdivisions of the mesoderm? (4)
Notochord, paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm
What will the notochord form?
Spinal cord
What will the paraxial mesoderm develop into?
Ribs and muscles
What will the intermediate mesoderm develop into?
Kidneys and gonad
What will the lateral plate mesoderm form?
Blood, peritoneum, etc.
What protein induces specialisation of ectoderm cells in neural tube formation?
Sonic hedgehog
What evidence is there that the notochord conveys information to ectoderm to induce neural tube formation? (2)
- Transplantation of second notochord leads to duplicated neural tube
- Any ectoderm transplanted next to notochord will be induced to form neural tissue
How many points of closure of the neural tube are there?
5
What dog breed has genetic predisposition to spinal dysraphism?
Weimaraner dogs
What are the types of animal movement?
Powered and unpowered rolling, slithering, legged
What phases do limbs undergo?
Protraction and retraction
What is flexion?
If the flexor angle is less than 180 degrees and decreasing
What is extension?
If the flexor angle is increasing
What are the 4 major equine gates?
Walk, trot, canter, transverse gallop
What is the fastest endurance gait for horses?
Trot
What is a 1 beat gait?
Stotting/pronking
What are 2 examples of unusual 2 beat gaits?
Pace and bound
What is an example of a 3 beat gait that isn’t canter?
Half bound
What are 2 examples of unusual 4 beat gaits
Rotating gallop and tölt
What are specialisations for increased efficiency of movement? (2)
Erect rather than sprawling stance, limb movement restricted to sagittal plance by collateral ligaments and muscles- no wasteful sideways movement
How are limbs specialised to increase stride length? (4)
Unguligrade means limbs are longer; mobile scapula; suspended plane; sagittal plane spinal flexion
How is a low distal mass achieved?
Loss of distal bones and digits, proximal muscle bunching, flexion of all joints during protraction
What is a plantigrade stance?
Walking on feet from hock down to toes
What is a digitigrade stance?
Walking on digits
What is an unguligrade stance?
Walking on toe
Where are the most dramatic forelimb differences between species seen?
Distal to carpus
what is the most proximal bone of the forelimb?
scapula
what is the range of movements of the scapula?
protraction, retraction, compression, extension, rotation
What domestic species still have clavicles?
Cats and rabbits
What sort of joint is the shoulder joint?
Ball and socket joint
What is the range of movement of the shoulder joint?
Flexion and extension
What is the name of the joint between the scapula and humerus?
shoulder joint
what does the shoulder joint not have?
collateral ligaments
what ligamental muscles support the shoulder joint?
infraspinatus laterally, subscapularis medially
what is the name of the joint between the humerus, radius and ulna?
elbow joint
which is the main weight bearer the radius or ulna?
radius
what are the names of the proximal carpal bones? (M to L)
radial, intermediate, ulnar, accessory
what are the names of the distal carpal bones? (M to L)
first, second, third, fourth
In what species are all carpal bones present?
pigs
in which species is the 1st carpal bone missing or very small?
horses
in which species are the radial and intermediate carpal bones fused?
carnivores
in which species is the 1st carpal bone absent and the 2nd and 3rd fused?
Ox
How many joints does the carpus comprise?
3
what is the antebrachiocarpal joint called in horses?
radiocarpal joint
which carpal joint has the greatest range of motion?
antebrachiocarpal joint
what sort of joint is the antebrachiocarpal joint?
hinge
what sort of joint is the intercarpal joint?
hinge
what sort of joint is the carpometacarpal joint?
gliding joint
what does the accessory carpal bone in horses articulate with? (2)
radius and ulnar carpal bone
what species has some reduction of the 1st digit (dew claw)?
dog
which species has an absent 1st digit, and smaller 2nd and 5th digits compare to 3rd and 4th?
pig
which species has an absent 1st and 2nd digit, common MC bone for 3rd and 4th and 5th represented by tiny MC bone?
ruminant
which species has an absent 1st and 5th digit, reduced 2nd and 4th digit only represented by small metacarpal bones?
horse
what are sesamoid bones?
small bones lying within or next to tendons or muscles
what is the function of sesamoid bones?
ensure the pull of muscles/tendons transmitted smoothly around bends
what is the carpus called in horse?
knee
what is the MCPj called in horse?
fetlock joint
what is the region between the fetlock and hoof called in the horse?
pastern
what is the DIPj called in the horse?
coffin/pedal joint
what is the femorotibial joint known as in the horse?
the stifle
when does somitogenesis start?
during neural tube closure prior to embryonic folding
where do somites develop from?
paraxial mesoderm
what do somites give rise to
the axial skeleton and dermatomes
where does the first sign of segmentation in somitogenesis occur?
in cervical regions- spreads caudally
which somite cells will form bones of the axial skeleton?
those closest to the neural tube as the receive the most signal
what are bones of the axial skeleton formed from?
sclerotome
what 2 layers do somite cells further from the neural tube separate into?
myotome and dermatome
what does myotome give rise to?
muscles of the main body (some cells migrate into limbs for limb musculature)
what will dermatome give rise to?
dermis
how many sclerotomes contribute to 1 vertebra?
2
what will happen if somite is transplanted more cranially?
will make structures appropriate to original site
which gene family is required for correct somite programming?
Hox genes
what is cervical vertebral instability?
abnormalities in the structure of the vertebrae, the ligaments that connect, or the disks between them
what is cervical vertebral instability know as?
wobbler syndrome
in which species of dog are cervical vertebral instability most common? (2)
Great Danes and Doberman Pinschers
what are hemivertebrae?
abnormal bony developments of 1 or more vertebrae
what does hemivertebrae severity depend on?
what part of the spinal cord is affected and whether there is compression of the spinal cord
what causes the kinked tail in screw-tailed dog breeds?
hemivertebrae in the tail region
what gives rise to the septum transversum?
thickening of mesoderm
what forms the gut tube?
endoderm
what process creates the gut tube and main body cavities?
ventral folding
what is the precursor of the diaphragm?
septum transversum
what is the most serious type of hernia?
diaphragmatic
what is the chondrin matrix of cartilage made of?
sulphated mucopolysaccharide gel and type 2 collagen fibres
what is the function of collagen in the cartilage?
resists tension
what is the function of mucopolysaccharide gel in the cartilage?
resists compression
what is cartilage produced by?
chondroblasts
what is cartilage often surrounded by?
perichondrium- flattened connective tissue layer
what are the types of cartilage? (4)
hyaline skeletal, elastic skeletal, fibrocartilage skeletal, articular
what are the characteristics of hyaline skeletal cartilage?
simplest type, may mineralise in old age
what are the characteristics of elastic skeletal cartilage?
contains elastin fibres
what are examples of hyaline skeletal cartilage? (2)
upper respiratory tract, ventral ribs
what are examples of elastic skeletal cartilage? (2)
external ear, upper respiratory tract
what are the characteristics of fibrocartilage skeletal cartilage?
tougher, often sheets, alternating layers of hyaline cartilage and collagen
what are examples of fibrocartilage skeletal?
intervertebral discs, symphyses, scuta, labra, menisci, discs
what are the characteristics of articular cartilage?
complex, partly fibrous/partly hyaline, collagen fibres mostly arranged radially to resist compression in region closest to bone
what is the matrix of bone composed of?
1/3 type 1 collagen, 2/3 hydroxyapatite with adsorbed calcium carbonate
what cells are involved in bone formation and destruction?
osteoblasts and osteoclasts
what are the classifications of bones by location?
axial, appendicular, cranial, postcranial
what are the classifications of bones by morphology?
long, short, flat, irregular, sesamoids
what are the classifications of bones by embryology?
somatic, visceral, sesamoids
what is the epiphysis?
the ends of long bones
what sort of bone is the epiphysis?
cancellous
what is the diaphysis of long bone?
the shaft
what is bone called when the epiphysis meets the diaphysis?
metaphysis
what is the periosteum?
the outer layer of bone, toughest part
what lines the marrow cavity?
the endosteum
how are the Haversian canals connected?
oblique Volkmann’s canals
what is each osteon made up of?
concentric cylinders of matrix interspersed with lacunae
what are trabeculae?
spicules in cancellous bone
what are the types of marrow?
red and yellow
what fracture plane does tension create?
transverse
what fracture plane does torsion create?
helical
what is a synostosis?
a joint made up of bone
what is a synchondrosis?
a joint where 2 bones are joined (fused) by cartilage
what is a symphysis?
a joint where 2 bones are joined by fibrocartilage
what is a syndesmosis?
a fibrous only attachment
what is a gomphosis?
the fibrous tooth socket and tooth connection
what is the other term for diarthroses?
synovial joints
what are synovial joints?
more mobile joints with specialised fluid and cartilage
what is the alternative name for a ball and socket joint?
enarthrosis
what is the alternative name for an ellipsoidal joint?
condylar
what is the alternative name for a saddle joint?
sellar
what is the alternative name for a hinge joint?
ginglyus
what is the alternative name for a pivot joint?
trochoid
what is the alternative name for a sliding joint?
arthrosis
what is the most mobile type of joint?
ball and socket joint
how many axes of movement does a ball and socket joint have?
3
how many axes of movement does an ellipsoidal joint have?
2
how many axes of movement does a saddle joint have?
2
how many axes of movement does a hinge joint have?
1
how many axes of movement does a pivot joint have?
1
what is an amphiarthrosis?
1 symphysis and 2 diarthroses
what are the 2 types of cell in synovial membrane?
secretory type B synoviocytes and phagocytic type A synoviocytes
what does synovial membrane secrete?
synovial fluid
what are the functions of synovial fluid? (2)
lubricant, nutrients and gases diffuse into fluid from synovial membrane and capsule, fluid then nutrifies and aerates articular cartilage
what underlies the synovial membrane?
areolar connective tissue
what is outside the areolar connective tissue?
thick white fibrous capsule
what is the role of collagen in articular cartilage?
resists tension
what is the role of proteoglycans in articular cartilage?
attracts water so resists compression
what does the joint capsule provide?
structural support for joint, lots of nerves which allows proprioception and respiratory reflexes
what are discs and menisci?
additional fibrocartilaginous ingrowths which separate joint into 2 compartments
what are labra?
fibrocartilaginous lips/extensions to a joint surface
what are bursae?
small synovial spaces between bones and tendon/muscle/skin
what is osteoarthritis?
when the joint degenerates beyond the ability of natural intrinsic repair mechanisms
what are the types of muscle?
skeletal striated, cardiac striated, smooth muscle
what is the range of a muscle?
how much it can contract
what is the force of muscle contraction proportional to?
the number of myofibrils in parallel
what is the range of a muscle parallel to?
number of sarcomeres in series
what is the simplest type of muscle?
strap
what direction are the fibres in a constrictor muscle?
same direction as the ring
what direction are the fibres in a dilator muscle?
opposite to the ring
what is an extrinsic muscle?
limb to limb
what is an intrinsic muscle?
within limb
what is the epimysium?
the outermost layer of connective tissue around muscle
what is the perimysium?
the middle layer of connective tissue around fascicle
what is the endomysium?
the inner layer of connective tissue around muscle fibres
what is a fascicle?
a bundle of muscle fibres surrounded by perimysium
what is the prime mover in antagonistic pairs?
the agonist
what do antagonistic pairs allow?
smooth, controlled movements
what is a synergist?
a muscle which prevents the action of other muscles from being impaired
what are the 2 types of synergist?
capsular and ligamentar
what is the role of capsular muscles?
stabilise joint capsules
what is the role of ligamentar muscles?
constrains movement
what is the convention of polyarticular muscles?
act at the most distal joint they cross
what is torque?
the ability of a force (muscle) to cause rotation of a mass (limb segment) about a pivot (joint)
what are tendons?
strong fibrous connection at ends of muscles to bone (continuation of epi-, peri- and endomysia)
what are the 2 types of tendon?
funicular and aponeurotic
what is a funicular tendon?
a cord-like tendon
what is an aponeurotic tendon?
a sheet-like tendon
what are the functions of tendons? (4)
direct muscular force, store and release EP, absorb sudden forces, amplify rapid movements
what is the other name for scuta and retinacula?
annular ligaments
what is the function of scuta and retinacula?
decrease the perpendicular distance of muscle from pivot which decreases torque
what are the functions of sesamoid bones? (3)
prevent tendons form flattening and reduce friction, increase perpendicular distance from pivot so increase torque
