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[Front]

Neurocranium/ Chondrocranium

[Back]

the braincase + the sensory capsules, arises form neural crest cells, cartilaginous in origin.

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Vertebre from and function - Details

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Neurocranium/ Chondrocranium

The braincase + the sensory capsules, arises form neural crest cells, cartilaginous in origin.

Is primitive found in insectivores and juvenile platypuses

Cusps Tropospheric

Arises from neural crest cells, forms branchial arches, leads to evolution of jaws

Splanchnocranium

Low crowned carnivores, cusps are separate and rounded

Bunodont

Surrounds other cranium and is the outermost skull, arises from primitive dermal armour, forms sides and roof of brain case and most of the bony lining of the roof of the mouth, enchases much of the Splanchnocranium.

Dermatocranium

Cusps forming transverse ridges found in rhinos and elephants

Lophodont

Development of holes in scull allowing change in jaw attachment and development of secondary palate leading to the ability to eat and breathe at the same time, this was key to the success of endotherms so that they could eat more with ease, also helpful for herbivores who must consume and chew allot.

Fenestra

Cusps are moon shaped, found in most herbivores

Selenodont

Includes cerebral cortex, thalamus and hypothalamus, all vertebrates have epithalamus to regulate biological rhythms, thalamus to control sensory input and hypothalamus to regulate body temp, water, hormones.

Forbrain

High crowned herbivores

Hypsodont

Includes sensory and motor tegmentum, includes optic lobes and lobes relating to inner ear.

Midbrain

Many individual teeth fused together at their base, separate cusps may still be visible.

Tooth plates

Includes pons conveying information from the forebrain, cerebellum modifies and maintains output, regulates equilibrium and coordinates motor function and medulla oblongata regulates respiration heart rate and intestinal motility.

Hindbrain

Neural arch- protecting the neural chord Centrum- surrounding notochord Hemal arch- protecting caudal blood vessels and processes that articulate with one another and the ribs to limit flexion and torsion.

Spine is comprised of

Few changes in hindbrain, cerebellum enlarged and became more complex for better motor control, forebrain increased in size for more complex behaviour, decrease in size of midbrain.

Evolution of brain from fish to mammals

Concave in the front and convex in the back, present in reptiles

Procelous vertebra

Convex in front and concave in back, present in most salamanders

Opisthocelous Vertebra

Flattened at both ends, present in mammals

Acelous Vertebra

Saddle shaped at both ends, present in birds

Hetroscelous Vertebra

Cervical vertebrae- neck, Thoracic- breast and ribs, Lumbar- belly, Sacrum- pelvis, Caudal- tail.

Regionalisation

Early vertebrae ribs articulated with every vertebrae running whole length of the body, now they are limited to the thoracic region, the sacral rib is bony in birds but cartilaginous in mammals , sharks are dorsal ribs.

Ribs

Tetrapod structure, an unpaired ventral structure anchoring to ribs and clavicles. None found in early amphibians but are found in them today, all amniotes have then and in birds they are very large.

Sternum

Fish lack them, amniotes have specialised vertebrate to move the skull. Amphibians have one specialised vertebra or 2, mammals have 7 and birds have extra long cervical vertebrae 12-20.

Cervical Vertebrae

Supports the pectoral limbs or fins, evolved first and is more complex and larger than the posterior girdle.

Anterior,shoulder or pectoral girdle

Supports the pelvic fin or limb, evolved after the pectoral and is smaller and less complex.

Posterior, hip or pelvic Girdle

Stability in forward movement, steering, muscles at base provide power to them, in aquatic species posterior fins provide propulsion and pectoral fins provide steering.

Functions of paired limbs

Pectoral fins are stronger and more firmly related to the axial skeleton then pelvic fins, differences in musculature allows the shape of the fins to be controlled, allowing variation in speed and movement.

Telos limbs

Composite structure formed of replacement bone (endochondral) & dermal elements. Pelvic- all endochondral bone, ilium, ischium and pubis. Pelvic- was in early amphibians a triangle shape, varies in shape in reptiles, in birds is large and firmly attached to the synsacrum, in mammals they have a long expanded ilium.

Girdles

Found in marsupials that articulate with the pubic bones possibly to support the pouch or gripping young.

Paired epipubic bones

Structures are uniform and specialised for flight, wings have 3 digits.

Bird limbs

Short, splayed to the side of the body, their trunk is lifted from the ground with difficulty when walking

Amphibian limbs

Use undulations of spine to twist girdles side to side , have 4 digits on the hand and 4-5 on the foot, 1-3 in each toe. Has marrow cavities in long bones.

Salamanders limbs

Many still have limbs far from the sides of the body, hind limbs are larger and stronger.

Reptile limbs

Legs must be relatively long in relation to other parts of the body, distal segments of the legs usually lengthen more then the proximal, cursorial undulations tend to have radius as ling or longer then humerus, and tibia as long or longer then femur. Foot is longer then middle limb segments.

Ditigrade- toe walking, dogs and cats, Unguligrade- fast long limbs, horses Plantigrade- short limbs flat food, humans and bears

Foot structure

Evolved form urochordates and Cephalochordata and vertebrata, all evolved form filter feeding ancestors with tentacles. The earliest vertebrates were osteoderms with a brain case 55mya. The brain case evolved in gastrodermis form the 1st and 2nd gill arches. It is the possession of the skull that make them chordates.

Chordates

A supportive rod, core comprised of cells with thick membranes, closely pressed together and fluid filled. Enclosed in a tough connective tissue sheath, prevents bod shortening and allows side to slide flexion and is the cite of muscle attachment

Notochord

Endothermic animals in cold environment’s are lager in size then the same species in warm environments.

Bergmans rule

Intra-individually: growth, Inter- individually: between individuals, Inter-specifically: between species, Positive Allometry: increase in independently from other limbs, Isometry: growth where proportions of all limbs remain.

Changes in shape

Compressive forces

Tensile force

Shear force

A specialised connective tissue, C cells embedded in an extracellular matrix, comprised of protein fibres, principally elastin and collagen. Has no blood vessels or Nevers only external ones on the fibrous sheath.

Cartlidge

Hyaline cartridge

Relatively few collagen fibres, found in articular surfaces, like tips of ribs and trachea.

Many collagen fibres, resists tensile force, found in intertribal disks like knees

Fibrous cartilage

Many elastin fibres, appears spongy, makes it flexible and is found in external ear and the epiglottis.

Elastic cartilage

Dynamic calcified connective tissue, calcium and organic salts deposited in a regularly organised matrix around a central core. Provides support and attachments for soft tissue and is the major cite for blood production. Comprised of 60% in- organic dry weight mostly calcium hydroxyl crystals, and the organic collagen component. Arranged in osteons, has a direct vascular and nerve supply. Osteoblasts secrete new bone and Osteocytes maintain equilibrium.

Bone

Endochondral – from cartilage, ossification of cartilage for form bone Intramembranous- Dermal bone, has no precursor for example bones of lower jaw and skull.

Types of bone formation

Diaphysis- ossified shaft with medullary cavity, Epiphysis- secondary centres of ossification, metaphysis- transition between 2 phases, the actively growing region.

Endochondral long bones

Hyaline cartilage forms into bone, first the periosteal bone forms, then blood vessels enter the bone then it ossifies starting at the ends, when growth stops epiphyseal plate forms.

Ossification

Loss of bone in response to lack of use or continuous stress

Atrophy

Addition of new bone due to intermediate stress.

Hytrophy

Develop during embryonic development , myotomes expand into various areas of the body. They grow along the sides of the body forming the musculature associated with the vertebral column ribs and lateral body wall. Includes the skeletal muscles of trunk and tail, in repeated metameric segments.

Axial mussels

Repeated segments are very visible and separated by myosepta. The myomeres are divvied into dorsal and ventral masses by horizontal a septum exiting between the transverse process of the vertebrae.

Axial mussels in fish-

Epaxials- above the horizontal septum Hypaxial- below the horizontal septum. Ira alba- separates 2 sides of the body

Separation of myomeres

Loss and fusion of bones, ulna is enlarged to support feathers, only 3 digits in wings, hind limbs tibia fused to tarsal to form tibiotarsus, distal tarsus fused to metatarsals creating tarsometatarsus. Loss of teeth. Sternum with large keel for flight muscles. Last few vertebra are partially fused to support tail.

Bird skeleton

Trends of evolution

Reduction, elaboration, loss of elements, development of temporal fenestra, secondary palate.

Enamel- outer tough layer(hardest substance in the body), Dentin-herbivores have exposed dentin to allow enamel to be sharpened as it wears down, Centrum- cements to bone.

Tooth structure

In sheet teeth, mammals

Thecodont

Teeth on conveyor-belt , fish

Acrodont

Side placed teeth, amphibians

Placodont

Teeth continuously replaced most non mammalian vertebrates

Polyphyodonty

Only 2 sets of teeth, most mammals

Diphyodont

Single set of teeth, odontocete whales

Monophyodont

Use burst speed, have extensive spine flexion, helps increase stride length, is energy expensive, ribcage is narrow and deep, clavicle is reduced or absent in fast organisms to allow scapula to swing freely.

Cheetahs

Feet shrink, loss and fusion of fibula to tibia and ulna to radius, muscle mass located proximally to the limb, metatarsals/ metacarpals elongated and reduced, fusion or squaring of tarsals, carpals and tarsals often fused.

Lengthen limbs for speed

Depends on habitat and speed, may have more than one, classified by relative phase between feet.

Gait

Fraction of time foot spends on ground

Duty factor

Equally spaced foot fall. e.g. walking having a duty factor on >0.5

Symmetrical gaits

Foot fall not equally spaced, both pairs of limbs off the ground at some point and pairs tend to fall at same time, duty factor on <0.5

Asymmetrical gait

Fossorial animals specialised for digging show anatomical adaptations, increased force output, bones robust, no fusion/ reduction, strong claws and muscle mass well distributed through limbs.

Digging

Climbing/swinging, increased limb length, distal ends modified for grasping.

Brachiation

Is very common, has occurred more then 30x in skinks, natural string of evolution of limb- lessness like in snakes.

Limb reduction in reptiles

Skin, barrier for pathogens, resists mechanical injury, holds shape, osmotic regulation, thermal regulation, houses sensory receptors, can house defences like horns or poison glands.

Integument functions

Epidermis- superficial, multilayer epithelium with cells that synthesize keratin, basement membrane- bottom layer of epidermis a deep layer of close connective tissue and can be specialised into glands hair ect.

Integument components

Epidermis is single layer of cuboidal or columnar cells, secretes mucus and pigment, dermis is high ordered collagen, gives structural support and flexibility, cytostomes have no trace of scales. thin, moist and loosly attached to body.

Amphibian skin

Thin epidermis with 2 glads secreting 2 types of mucus, thin noncellular cuticle covers epidermis, keratin is absorbed, dermis mainly a fibrous layer containing collagen, no elastic fibres.

Lamprey skin

Found on sharks very similar to odontoids (tooth like scales), but without bony base, in bony fish scales don’t actually protrude through epidermis.

Placoid scales

Only in primitive fish, modified scales with layer of dentine formed by odinite like elements, diamond shaped, layers of enamel on upper layer and bone on lower.

Ganoid scales

Lungfish have them, very thin scales made of dense calcified organic matrix,

Lacmoid scales

Found in teleost fish, circular and fan shaped, derived form ganoid scales, thinner and arranged in overlapping rows, grown in annual rings continuously for whole life.

Cycloid and Ctenoid scales

Mostly in ectoderms, may be constant colour on colour or changing, complex control by hormones or neurological.

Chromatophores

Cells in dermis don’t contract or expand the streaming cytoplasm carries pigment, 3 successive layers of pigment, 1st xanthophores- yellow, orange and red, 2nd iridophores- silver and reflective, 3rd melanophores- black or brown.

Amphibian Chromatophores

Tough, dry, scaly skin, with hinged scales, thin epidermis with highly keratinised scales, thick dermis with melanophores.

Reptile integument

Has osteoderms, bone on the scales, in isolated blocks, responsible for keeled shape, with rich blood supply that circulates heat, also have sensory pores and hairs.

Crocodile skin

Come in different types, contour, primaries, secondaries, down, and filoplume, penguins have specialised sleek feathers for swimming and owls have specialised soft feathers to fly silently. Birds moult their feathers, some may prepare to moult in one go by staying in a safe area.

Feathers

Epidermis is comprised of several layers, has locally specialised skin in the form of hair, cells are keratinised and includes connective tissue, blood vessels, nerves, dermal papillae and smooth muscle.

Mammalian integument

Modified keratinised skin cells unique to mammals, used for thermal protection, myocytes to make colour have hare pili to erect hair, has guard hairs and inner thick soft underfur.

Hair

Appears white but is actually translucent, to be able to survive below -45c they have black skin to absorb more sunlight and translucent hair so light can shine through onto skin

Polar bears hair

Modified hair that grows annually (unlike hors that are permeant), is very energy expensive, can grow to 30kg, grows under skin called velvet that sheds off the antlers revealing bone

Antlers-

Provide protection and do not shed (except in prong-horns) inner cone of bone and outer skin.

Horns

3 sections, forebrain, Midbrain , Hindbrain.

Brain

More capillary beds open in the peripheral circulation of skin to increase blood flow transporting heat to the environment

Cooling

Blood transports warmth to deep tissues or carries away excess heat to body surface. Mediated changes in microcirculation to control heating and cooling.

Circulation and thermoregulation

Water more able to hold heat, flippers in cold water could lose top much heat. Mesh rete in intertwining network between outgoing arteries and returning veins, establishes counter current heat exchange. Heat in arteries is almost completely transferred to returning blood in veins forming heat blocks, by time blood reaches flippers there is almost no heat to be lost

Heat loss in flippers

Is very sensitive, a specialised carotid rete at the base of the brain protecting against overheating. Many animals have highly folded tabernacle bones supporting extensive area of nasal membranes for evaporative cooling

Brain and heat loss

Turbinate bones, cool or heat incoming air and trap moisture. Heat- loss is highly variable due to wind and speed as little as 25% or as much as 400%.

Heat loss in birds

Huddling in emperor penguins alone they burn 0.2kg of fat to keep warm in a huddle they only need 0.1kg.

Behavioural thermoregulation

Deep diving seals drop in heart rate form 125b.p.m. to 10b.p.m. slowing heart rate lessens need for blood stream, is followed by vasoconstriction. Lungs have 55% of usual blood flow heart 15%, diaphragm 5% brain 108% and cerebellum 93%. Mainly reducing flow to lungs.

Bradycardia

Carry blood away form the heart, have 3 layers, flattened epithelium and supporting connective tissue, smooth muscle and elastic fibres. Elastic fibres allow expansion and pressure for blood flow. Small arteries move into arterioles and capillaries ,made up of a single layer of squamous epithelium. Are progressively smaller the further form heat with more smooth muscle and less elastin fibres.

Arteries