Locomotor

selection pressures of locomotion (evolutionary perspective)

resources (habitat, food, mates), environment (temperature, weather, access), biological (predators, pathogens)

what are the three main things the locomotor system needs to do

support body mass, move center of mass, move limbs

COM

centre of mass

what features support speed and agility

muscle bulk, body mass, skeletal arrangement, grippy “footwear”

what is muscle’s role in speed and agility

muscle produces forces within the limb that allow support and movement of joints

what do individual vertebrae allow

spinal mobility and flexibility

why is skeletal arrangement important for muscle function

influences the actions that muscle can have

what is the importance of grip (traction)

allows increased agility, performance, and maneuverability

examples of traction (structures)

pads, multiple digits, accessory structures like claws

what features support endurance and efficiency

elastic tissue (eg tendons), skeletal arrangement (pectoral girdle specializations, limb length and weight)

what is the tradeoff of muscle for tendon

manipulative ability and control

GRF

ground reaction force

ground reaction force (GRF)

force exerted by the ground on a body in contact with it

what is the distribution of GRF on forelimb vs hindlimb

forelimb - 60%, hindlimb 40%

what is the difference between the forelimb and hindlimb GRF (percentage)

forelimb GRF around 30% higher

how do tendons support endurance and efficiency in the herbivore

they stretch and store energy, recoiling to put energy back into the locomotor system - a cycling of energy v.s. generation

what design of leg is preferred in the hervivore

long and light

why do herbivores prefer long and light legs

long - longer steps and strides, more distance for given amount of energy; light - lower cost of energy for swinging legs

unguligrade

standing on most distal bone

plantigrade

standing on plantar surface of foot

what is the main difference in pelvic girdle between bipedals and quadripedals

bipedals have clavicle (rigid junction between forelimb and body), quadripedals have scapula joined onto body purely by muscle (no bony joint attachment)

what do quadripedals have instead of a clavicle

mobile scapula

why is a mobile scapula an advantage to quadripeds

scapula is free to move, meaning the forelimb can protract and retract to great degrees, increasing stride length and efficiency of locomotion

bone

a type of connective tissue made up of cells suspended in a matrix, made of 65% hydroxyapetite and 30% collagen (and other organic materials)

bones

organs made up of bone tissue

what do you call the long part of a bone (middle)

diaphysis

epiphysis

one of the rounded ends or tips of long bone that ossify from one or more secondary centers of ossification. separated from the diaphysis by the epiphyseal plate

epiphyseal plate

the thin layer of tissue that separates the epiphysis from the diaphysis

diaphysis

the main or midsection of a long bone, comprised of cortical bone and marrow

metaphysis

the neck portion of a long bone, transitional region between the epiphysis and diaphysis. contains growth plate, helps cushion and protect bones from wear and tear, maintains structural integrity of bone by producing new bone tissue as needed

cortical bone

compact bone. dense and strong type of bone tissue that forms outer layer of bones. provides structural support and protection. high density and minimal porosity

trabecular bone

spongy bone. lattice-like tissue found inside skeleton, primarily at ends of long bones and within vertebrae. sits inside cortical bone. absorbs shock, distributes mechanical loads, houses bone marrow

advantages and disadvantages of trabecular bone

extremely light, suitable for flight, holds changes in loads well, allows flexibility and strength in weight-bearing joints. vulnerable to degradation, vulnerable to fractures and breaks

advantages and disadvantages of cortical bone

holds loads extremely well, supportive of large weights, strong and rigid. less flexible, not advantageous for flight or speed

medullary cavity

the central cavity of bone shafts where red/yellow bone marrow (adipose tissue) is stored. walls composed of cortical bone, surrounded by trabecular bone. lined with thin, vascular membrane (endosteum)

endosteum

thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. will be reabsorbed during long periods of malnutrition

flat bones (structural differences non-long bones)

no medullary cavity, 2 layers of compact bone surrounding either spongy bone or air

short bones/irregular bones (structural differences non-long bones)

no medullary cavity, develop from single centre of ossification

osteogenic cell

stem cell. undifferentiated mesenchymal cells found primarily in periosteum, endosteum, and bone marrow. can differentiate into several cell types, but primary role is to generate new bone tissue. only bone cells capable of mitosis

osteoblast

cells that synthesize bone tissue from collagen and mineral. forms bone matrix. arise from differentiation of osteogenic cells. form closely packed sheet on surface of the bone, from which cellular processes extend through the developing bone

osteocyte

most abundant and longest lived cells in mature bone. begin as osteoblast. deposits bone matrix around itself, becoming entombed, then shrinks and sends out dendrites, shifting from builder to sensor. senses mechanical forces, regulates mineral levels, orchestrate work of bone building and bone destroying cells, send hormone-like signals to organs

osteoclast

bone cell that removes bone tissue. crucial for maintenance, repair, and remodeling of bones. found in resorption bays/cavities of bone. release organic acids that degrade bone’s mineral component, and enzymes that can dissolve organic osteoid matrix proteins.

periosteum

membrane that covers exterior of bone (except at articular surfaces (within joint space)). has two layers, is protective and relatively thick. osteogenic. sites of sensory nerves, blood, and lymphatic vessels

articular cartilage

lines the joints of long bones in synovial joints, providing low friction surface and distributing loads. avascular, aneural, composed of mostly collagen, proteoglycans, and 65-80% water.

how many layers does periosteum have

two

fibrous layer - periosteum

outer layer. made of dense, irregular connective tissue and contains collagen fibers, blood vessels, nerve fibers

cellular layer - periosteum

inner layer. composed of osteoblasts, osteoclasts, and undifferentiated mesenchymal cells

endosteum

lines medullary cavity. thin vascular membrane. is osteogenic and osteolytic

osteogenic

derived from or made up of bone-forming tissue. typically means - containing osteoblasts

osteolytic

the breakdown, loss of, or resorption of bone tissue. typically means - containing osteoclasts

osteon

cylindrical structure that is the fundamental functional unit of compact bone. consists of lamellae of compact bone tissue that surround the Haversian canal. collagen fibres run in different directions in neighboring lamellae. still allows give, but is more resistant to twisting force.

Haversian canal

series of tubes in cortical bone that allow blood vessels and nerves to travel through them to supply the osteocytes. each generally contain one or two capillaries and many nerve fibers. formed by lamellae.

lamellae

thin, plate-like structure very close to each other with open space between

purposes of bone surface markings

leverage, muscle attachment, response to strain within bone, articulations with other bones

surface markings

anatomical features, such as projections, depressions, and openings, that serve as passageways for nerves and blood vessels, attachment sites, or joint surfaces for bone. vary depending on bone’s function and location

sesamoid bones

small, round bones that are embedded within tendons or ligaments. most commonly found in hands and feet. ease tendon path and prevent excessive tendon wear. increases moment arm of muscle

examples of sesamoid bones

patella, fabellae (dog), proximal (horse)

muscle belly

thick, central, contractile part of a skeletal muscle. fleshy section between origin and insertion tendons. where force is produced. largest structure in muscle, most palpable. smaller units within that contribute to overall structure.

tendon

anchors muscle to skeleton. may be long or incredibly short. typically continuous with layer of aponeurosis. flexible but inelastic, made of strong fibrous collagen tissue

aponeurosis

flattened tendon by which muscle attaches to bone or fascia. broad, flat sheet of dense fibrous connective tissue. elastic and act as insertion sites for muscle fibers

what is the difference between tendon and aponeurosis

tendon - tough, flexible, inelastic band of connective tissue (collagen) that attaches muscle to bone; aponeurosis - thin, elastic sheet of fibroblasts covers portion of muscle belly and that attaches muscle to bone or fascia

epimysium

fibrous tissue envelope that surrounds skeletal muscle. ensheathes muscle and protects it from friction against other muscles and bones. keeps smaller units within muscle belly together

perimysium

connective tissue sheath made of dense irregular tissue that surrounds individual muscle fascicles. membrane around exterior of fascicle

fascicle

grouping of muscle cells enveloped by perimysium. groupings of these surrounded by epimysium create the muscle belly

muscle fibre

single muscle cell. elongated, striated, and contains multiple nuclei. contains myofibrils. come in bundles to make the fascicle. become specialized when grouped

myofibril

basic rod-like organelle of a muscle cell. very fine contractile fibres that extend in parallel columns of striated muscle fibres. made of thick and thin myofilaments which give muscle its striped appearance. structures that actually contract and shorten for movement

endomysium

thin layer of aerolar connective tissue that ensheathes each individual muscle fibre/cell. contains capillaries and nerves. lies over the sarcolemma

sarcolemma

cell membrane of muscle fiber. acts as selectively permeable barrier. at each end of muscle fibre, the surface layer fuses with a tendon fibre, and the tendon fibres in turn collect into bundles to form muscle tendons

sarcomere

smallest functional unit of striated muscle cells. made of thick and thin filaments. main function s regulation of muscle contraction. myosin head (thick) binds with actin filaments (thin) to form a cross bridge when signal recieved for contraction. actin filaments then slide along myosin as result of the head bending and pulling actin inward. troponin and tropomyosin proteins of thin filaments prevent binding of actin and myosin until signal for contraction via ATP hydrolysis obtained

where are healthy nuclei located in muscle cell

peripherally located on edge of muscle fiber

where are unhealthy nuclei located in muscle cell

centrally or internally located, which indicates disease or damage

why do muscle cells have multiple nuclei

increased regenerative capacity. muscle capable of enlarging, repairing easily when torn

voluntary control muscles

muscles that are controlled consciously through the somatic nervous system. biceps, triceps, facial muscles. etc.

involuntary control muscles

muscles that are function outside conscious control through the autonomic nervous system (ANS). cardiac, digestive, blood vessels, etc.

two types of involuntary control muscle

smooth and cardiac

smooth muscle

involuntary control muscle. found in walls of hollow organs and tubes, such as digestive tract, urinary bladder. responsible for functions such as blood vessel regulation, digestion, and peristalsis. no striations, single nucleus. longer contractions

cardiac muscle

involuntary control muscle. found only in the heart. responsible for pumping blood throughout the body. striated, single central nucleus. irregular arrangement with intercalated disks

what is the purpose of the intercalated disks in cardiac muscle

control ion movements - synchronize across the tissue

origin (muscle)

where muscle begins. stationary or more fixed attachment of muscle. remains anchored during contraction. usually proximal in limbs.

insertion (muscle)

where muscle ends. where muscle attaches to bone that moves when muscle contracts. moves during contraction, allowing muscle to generate motion or apply force.

muscle architecture

the arrangement of muscle fibres (relative to axis of force generation) that determines a muscle’s mechanical function

force

the push or pull on an object with mass that causes it to change velocity

work

force times change in distance

power

rate of performing work - change in work over change in time

pennate muscle

muscle with fascicles (short fiber) that attach at slanting angle to internal tendon or aponeurosis. increase PCSA but decrease ROM

ROM

range of motion

PCSA

physiological cross sectional area

what is directly proportional to muscle PCSA

muscle force

parallel muscle

muscles with fibres that run with (in parallel to) the line of pull of the muscle. typically very long, more sarcomeres in series. low PCSA, large ROM. potential for increased velocity of contraction

tendon structure

hierarchal, similar to cells of muscle. comprised mainly of collagen, which makes fibrils, fibers, subfascicles, and fascicles within tendon. under microscope is extremely long, thin, wavy. not very cellular tissue.

roles of tendon

minimizing distal limb mass (eg horse), joins muscle to bone, elastic energy storage, energy conservation, power aplification

how is a tendon like a spring

act to store and release elastic energy

why are tendons more economical

having long tendons means we can have short muscle fibers. short muscle fibers don’t contract very much, which reduces energy cost of developing muscle force.

what type of fibers (long or short) are in the interosseus, and SDF & DDF in horse

short - so short they look vestigial

what do tendons amplify

muscle power

what is faster, a recoiling stretched tendon or a shortening muscle

recoiling stretched tendon

why are tendons power amplifiers, in terms of work

since power = rate of doing work, when tendons operate, only a small amount of work is done but in a much shorter time. this means power output will be much higher

lacertus fibrosus

bicipital aponeurosis. broad, membranous band of connective tissue that extends from the biceps brachii tendon across cubital fossa. protective layer for the brachial artery and median nerve

why are horse legs a “biological catapult”

biceps stretch during stance when carpus is locked in extension. the LF stores elastic energy. when carpus buckles in late stance, the stored energy is rapidly released, swinging the leg forward

synovial joint

most common type of joint. most movable. articulating bones separated by fluid filled space. joint is surrounded by synovial membrane, strengthened by joint capsule