ANFS 240 - Muscles & Joints

Lecture

Muscle

soft tissue made up of specialized cells called myofibers, main purpose is contraction

Cardiac muscle

Specialized type of muscle that makes up the heart wall, striated and involuntary

Epicardium

What is cardiac muscle externally surrounded by?

Smooth Muscle

specialized type of muscle that lines blood vessels and viscera (internal organs), involuntary, not striated

Skeletal Muscle

striated & voluntary, makes up half of the weight of an animal, typically consumed as food

Epimysium

(1) dense connective tissue that surrounds the entire muscle belly

Perimysium

(2) loose layer of connective tissue that surrounds small bundles of myofibers

Endomysium

(3) thin connective tissue that surrounds each myofiber

Tendons

epimysium, perimysium, and endomysium all meet at the end of each muscle belly, this is how most muscles attach to bone

contraction

shortening the length of the myofibers, & therefore the muscle as a whole

relaxation

passive process that allows the muscle to return to its original shape and position

locomotion

movement of the animal in a direction

tendinous

(orange) muscles terminate in tendons that attach them to the periosteum of the bone, not the same as a ligament

fleshy

(blue) apparent direct attachment of bone to muscle via very short tendons

aponeurotic

a flat sheet of tendinous connective tissue that attaches muscle to bone, common in trunk muscles

apneurosis

flat, broad tendon

agonist

responsible for primary motion of a joint

antagonist

muscles that opposes the motion of the agonist

synergist

aids the motion of the agonist

fixator

stabilizes the proximal end of the limb while the distal end moves

pronation

(blue) palmar/plantar side rotates medially toward the palmar/plantar direction

supination

(red) palmar/plantar side rotates laterally toward the dorsal direction

parallel

(1 & 2) all fascicles run the same direction, greatest amount of contraction → not efficient, less strong

Pennate

(3, 4, & 5) fascicles run at an angle, less shortening → stronger contractions

Unipennante

(3)

Bipennate

(4)

Multipennate

(5)

Sphincter

(orange) fibers encircle an opening and contract around it

Origin

(red), more proximal or central muscle attachment to bone

Insertion

(blue), more distal or peripheral attachment, typically moves with extremity & will be drawn to the origin

Fascia

connective tissue that separates & surrounds larger structures

Superficial fascia

loose connective tissue that is underneath the skin

Intrinsic muscle

muscles whose origins and insertions are both within the limb

extrinsic muscle

girdle muscles whose origins are on the trunk and insertions are on a limb

Pectoral Muscles

forelimb girdle muscles, ventral, responsible for adduction of the forelimb, major flight muscles in birds

pectoantebrachialis

Origin: manubrium

Insertion: humerus (just proximal to the elbow)

Function: adduction of the forelimb

Pectoralis Major

Origin: body of the sternum

Insertion: diaphysis of the humerus

Function: adduction of forelimb

Pectoralis Minor

Origin: body of the sternum

Insertion: ventral humerus

Function: adduction of the forelimb

Xiphihumeralis

Origin: xiphoid of the sternum

Insertion: ventral humerus

Function: adduction of the forelimb

Sternomastoid

V-shaped paired muscles

Origin: cranial manubrium

Insertion: hyoid bone

Function: flex the head (pair) or turn the head (singly)

Sternohyoid

Ventral, paired strap-like muscles

origin: first costal cartilage and manubrium

Insertion: hyoid bone

Function: retracts the hyoid bone

Latissimus Dorsi

dorsal and lateral muscle, large, broad, flat - caudal to the trapezius

Origin: spinous processes of 4th and/or 5th thoracic and 6th lumbar vertebrae

Insertion: the medial side of the proximal humerus shaft

Function: retracts the limb, drawing the forelimb dorsocaudally. If limb is fixed, it advances the trunk forward

Brachiocephalicus

cranial girdle muscle, consist of two distinct muscles: clavotrapezius & clavobrachialis,

Origin: occipital bone and transverse process of cervical vertebrae

Insertion: lateral side of proximal radius and ulna

Action: shoulder extension; neck lateral flexion, raise shoulder and pull forelimb forward

Clavotrapezius

blue

Clavobrachialis

orange

Trapezius muscles

cranial and dorsal, made up of two parts

Acromiotrapezius

(5) cervical, thin, fan-shaped muscle, paired that both share an aponeurosis at their origin

Origin: dorsal spinous process of cervical vertebrae

Insertion: spine of the scapula

Function: elevate and abduct the forelimb

Spinotrapezius

(5’) thoracic, flat, dorsal, triangular muscle, caudal to acromiotrapezius

Origin: dorsal spinous process of the thoracic vertebrae

Insertion: spine of the scapula

Function: dorsal and slight caudal movement of the scapula - aids in advancing the forelimb

Deltoid muscles

two separate muscle bellies in the cat (spinodeltoid & acromiodeltoid)

Origin: scapular spine (at or near the acromion)

Insertion: deltoid tuberosity of the humerus

Action: flex the shoulder

Triceps brachii

3-headed muscle, on the caudolateral forearm, agonist to biceps brachii during flexion

Lateral & Medial heads:

Origin: (L&M) Humerus, (Long head) caudal edge of the scapula

Insertion: olecranon of the ulna

Action: extend the elbow joint and flex shoulder when the elbow is in extension

Serratus ventralis

large fan-shaped muscle deep to the scapula, one of the main muscles attaching the forelimb to the trunk

Origin: transverse processes of C3-C7 + first 7 ribs

Insertion: deep surface of the scapula

Function: support the trunk

Gluteus medius

large, cranial rump muscle

Origin: lateral crest of the wing of the ilium

Insertion: proximal femur

Action: extend the hip & abduct the limb

Gluteus maximus

smaller rump muscle, superficial, caudo-distal to the hip joint

Origin: lateral border of the sacrum

Insertion: proximal femur

Action: extend the hip, abduct the limb

Caudofemoralis

only in cats, just caudal to the gluteus maximus

Origin: transverse process of the first coccygeal vertebrae

Insertion: lateral patella

Action: abduct & extend the pelvic limb

Hamstring muscles

What group does the biceps femoris, semimembranosus, and semitendinosus belong to?

Biceps femoris

very large muscle on the caudolateral side of the femur

Origin: ischiatic tuber of the os coxae

Insertion: proximal end of the tibia/fibula

Action: flexion of the stifle, extension of the hip

Semimembranosus

(blue) Clinical relevance, where to give vaccines, more medial

Origin: ischiatic tuber of os coxae

Insertion: proximal ends of tibia/fibula

Action: flex stifle, extend hip

Semitendinosus

(red) Clinical relevance, where to give vaccines, more lateral

Origin: ischiatic tuber of os coxae

Insertion: proximal ends of tibia/fibula

Action: flex stifle, extend hip

Gracilis

wide, thin muscle that covers the superficial aspect of medial thigh

Origin: ventral pelvic symphysis

Insertion: cranial border of the tibia

Function: flexion of the stifle, extension of the hip, adduction of the limb

Sartorious

thinner strap-like muscle on the inner thigh, more cranial than the gracilis

Origin: crest of the ilium

Insertion: patella & proximal tibia

Action: hip flexion, stifle extension, limb adduction

Quadriceps complex

What is a 4-headed muscle that extends the stifle, made up of vastus lateralis, vastus medialis, vastus intermedius, and the rectus femoris?

Vastus medialis

(red) 1/3 of Quadriceps complex

Origin: diaphysis of the femur

Insertion: tibial tuberosity & patella

Action: extend the stifle

Vastus Lateralis

(green) 1/3 of Quadriceps complex

Origin: diaphysis of the femur

Insertion: tibial tuberosity & patella

Action: extend the stifle

Rectus femoris

(blue) cranial to vastus medialis

Origin: ilium

Insertion: tibial tuberosity

Action: extension of the stifle/flexion of the hip

Vastus Intermedius

(red) 1/3 of Quadriceps complex

Origin: diaphysis of the femur

Insertion: tibial tuberosity & patella

Action: extend the stifle

Gastrocnemius

caudal muscle along the tibia/fibula, calf muscle, with 2 head: medial and lateral

Origin: patella and caudal surface of the distal femur

Insertion: calcaneus via the Achilles tendon

Action: extend the hock

Abdominal muscles

what muscle group has 4 muscles in total, form the wall of a cavity, that functions are: flexion the spine, labored exhalation, expulsion of urine, feces, and/or a fetus, and vomiting, and contain all large, flat muscles with large aponeurotic insertions?

External abdominal oblique

fibers run caudoventrally, abdominal muscle

Origin: last 9-10 ribs and thoracolumbar fascia

Insertion: linea alba via aponeurosis

Internal abdominal oblique

fibers run cranioventrally, abdominal muscle

Origin: last 9-10 ribs and thoracolumbar fascia

Insertion: linea alba via an aponeurosis

Transversus

(blue) deepest abdominal muscle, fibers run transversely (ventrally)

Origin: costal arch, lumbar vertebra, and ileum

Insertion: linea alba

Significant caudal aponeurosis (green)

Rectus abdominis

most ventral abdominal muscle, long and narrow

Origin: pubis

Insertion: costal cartilage

Diaphragm

What is the main muscle of respiration that’s a wide, thin muscle that separates the thoracic cavity from the abdominal cavity, contains 3 openings for the esophagus, aorta, and caudal vena cava, and moves cranially (expiration) and caudally (inhalation) to decrease/increase the thoracic volume?

Intercostal muscles

muscles between each rib

External: superficial and runs caudoventrally

Internal: deep and runs cranialventrally

Engaged during inspiration and expiration

Cutaneous trunci

thin, very large superficial sheet of muscle that spans the trunk, particularly well-developed ventrally in many large animals, “twitches” or shakes the skin in response to flies and other irritants

biceps brachii

relatively thick muscle lying on the cranial surface of the humerus, only one head in the cat

Origin: scapula

Insertion: radius

Function: flexes the elbow

Circulatory System

Network of vessels that carry fluid throughout the body, specifically blood for cardiovascular system and lymph for lymphatic system (significant part of the immune system)

Cardiovascular System Functions

• Carry oxygen throughout the body to tissues (collected in the lungs)

• Carry nutrients throughout the body to tissues (collected in the GI tract)

• Carry hormones throughout the body to tissues (collected from specialized endocrine glands)

• Remove waste from cells & deliver to organs for processing and elimination

Development of cardiovascular system

Early and common origin in the developing embryo, all are related and have specialized tissues unique to this system

Peripheral blood vessels

those that carry blood from the heart to tissues and return blood to the heart

artery

takes blood away from the heart, have very thick, strong walls, made of 3 layers, can withstand and support high blood pressure

arteriole

smallest arteries

Vein

brings blood back to the heart, thinner-walled than arteries, similar construction to arteries, but much thinner tunica interna, and a tunica media that is thinner and with far less elastic tissue (often collapsed unless blood pressure is increased), and has valves to prevent backflow because pressure is lower

Venule

smallest veins

Capillary

the tiny connections between arterioles and venules where the transfer of materials (oxygen, nutrients, etc) happens

Tunica interna

innermost part of the artery, specialized layer of connective tissue with an inner elastic membrane surrounding it externally; very smooth

Tunica media

middle layer of artery, thickest layer made up of elastic tissue and smooth muscle

Tunica adventitia

external layer of artery that is mostly fibrous, limiting the expansion of the artery and keeping it from stretching out and slowing down blood flow

What can backflow cause?

clots and obstructions

Capillaries

very narrow endothelial tubes, supported by very delicate connective tissue, allows for transfer of oxygen, nutrients, and waste to and from the blood due to how thin-walled they are

How does transfer of oxygen, nutrients, and waste occur?

fluid escapes into the tissue from the arteriole side due to higher pressure, then reabsorb fluid from venule end

capillary bed

network of capillaries that supplies blood and removes waste from organs

Where are capillary beds densest?

More “active” areas due to the increase in blood exchange

Sinusoids

specialized type of capillary found in organs like the liver, spleen, and bone marrow, wider than regular capillaries and often have fenestrations (small holes) in their wall which allow for larger compounds to flow in and out of the vessel

Flow of blood

Heart → Artery → Capillary → Vein → Heart

Heart

Central organ that pumps blood continuously that has rhythmic, self-sustaining contractions

Right atrium

3

Left atrium

5

Right ventricle

8

Left ventricle

10

Atria

thinner-walled, cranial/dorsal part of heart, stretchy, accepts blood