Anatomy Exam 3

What are the general characteristics of muscle cells

specialized for contraction, aggregated into bundles, elongated, arranged in parallel bundles, and contain actin and myosin

What are the specialized structures of muscle cells?

Sarcoplasm: cytoplasm (mostly contains the proteins myosin and actin)

Sarcolemma: cell membrane (surrounds the muscle cell and carries electrical signals)

Sarcoplasmic reticulum: modified ER (stores and releases calcium needed for contraction)

What are the three types of Muscle Tissue?

Skeletal muscle, Cardiac muscle, and Smooth muscle

What types of muscle tissues are striated (marked with a series of parallel lines, bands, stripes, or grooves) v non-striated

Striated: skeletal and Cardiac muscle

non-straited: Smooth muscle

How do skeletal muscle fibers develop?

1. Myoblasts are immature muscle cells that fuse together to form a long, multinucleated cell called myotubes

2. Myotubes differentiate (mature) into skeletal muscle fibers

3. Satellite cells remain alongside muscle fibers to help with muscle repair and limited regeneration

What are the characteristics of skeletal muscle and how does it attach to bone

Parallel, striated, multinucleated fibers with peripheral nuclei and rich blood supply

• Can NOT divide so limited regeneration (get from satellite cell)

• Attaches to bone through tendons made of collagenous fibers

What are the three connective tissue layers of skeletal muscle?

Endomysium: surrounds each muscle cell, containing capillaries

Perimysium: Surrounds bundles of muscle cells, contains larger blood vessels (fascicles)

Epimysium: surrounds entire muscle

What are myofibrils made of and what do they do?

Myofilaments: thick (myosin) and thin (actin)

• myofibrils contain the bands that create the striated (striped) appearance of skeletal and cardiac muscle (made of many repeating sacromeres)

What is a sacromere?

Functional unit of muscle, segment of myofibrils between two z-lines

• contains the myosin filaments (A-band)

What are the A-band and I-band, and what do actin filaments do

A-band: contains thick myosin filaments and remains constant (does not change in size)

I-band: region between adjacent A-bands, contains only actin filaments and shortens as actin filaments slide

• Actin filaments attach to Z-line and extend toward center of the sarcomere through I-band and partly into A-band

• Repeating sarcomeres with alternating A-bands and I-bands is what produces the striated appearance

What are T-tubules

Inward extensions of the muscle fiber's plasma membrane (sarcolemma) that carry action potentials deep into the muscle fiber, triggering muscle contraction.

What is a triad?

One T-tubule and two terminal cisternae (enlarged sacs of the sarcoplasmic reticulum (SR) that store calcium (Ca²⁺) needed for muscle contraction)

What is a synapse

Junction where a neuron communicates with another cell, such as a muscle or gland

(neuromuscular junction is the location where they communicate and it has the presynaptic, synaptic, and postsynaptic parts)

What happens at the neuromuscular junction

The presynpatic terminal of a motor neuron releases acetylcholine (ACh) into the synaptic cleft, which binds to receptors on the sarcolemma, intiating a muscle action potential along sarcolemma and into T-tubules, Terminal cisternae release calcium, Actin and myosin interact, sarcomeres shorten

How does the action potential spread through the muscle

Travels down the sarcolemma and down the T-tubules

What causes muscle contraction

shortening of sarcomeres

What is a motor unit?

single motor neuron axon and all muscle fibers it innervates

What are Type 1 muscle fibers

Slow-twitch, red, oxidative, fatigue-resistant

What are Type 2a muscle fibers

Fast-twitch, intermediate, oxidative-glycolytic, fatigue-resistant

What are type 2b muscle fibers?

Fast-twitch, white, glycolytic, fatigue-prone.

How do the soleus and extensor digitorum longus (EDL) differ?

Soleus: slow-twitch, oxidative, fatigue-resistant. EDL: fast-twitch, glycolytic, fatigable

skeletal muscle organization

Whole muscle → fascicle → muscle fiber → myofibril → sarcomere → myofilaments

What are the characteristics of cardiac muscle

Striated, mononucleated (one central nucleus), smaller branching cells that interconnect, and no satellite cells (meaning cant repair).

What are intercalated discs?

Connections between cardiac muscle cells containing desmosomes and gap junctions

What is the function of gap junctions in cardiac muscle?

Allow excitation to spread between cardiac cells for coordinated contraction.

How does cardiac muscle contraction begin?

Spontaneously through pacemaker cells; signals travel through conducting fibers, including Purkinje fibers.

How does cardiac muscle's blood supply compare to skeletal muscle?

Cardiac muscle has more capillaries because it is highly sensitive to lack of oxygen

What are the characteristics of smooth muscle?

Non-striated, involuntary, spontaneously active, maintains tone, and can regenerate.

What does the nucleus of smooth muscle look like?

Ellipsoid (elongated); may appear corkscrew-shaped during contraction.

How are smooth muscle myofilaments organized?

Arranged in multiple planes and anchored to the plasma membrane.

How do smooth muscle cells contract

Actin and myosin interact and slide past each other, causing the cell to shorten and thicken. Unlike skeletal and cardiac muscle, smooth muscle does not contain sarcomeres

Where is smooth muscle found?

Walls of hollow organs, blood vessels, digestive tract, uterus, respiratory and urogenital ducts.

What are myoepithelial cells?

Specialized contractile cells associated with exocrine glands, such as salivary and mammary glands. (basically smooth muscle cells are found in a variety of other organs)

What makes up the musculoskeletal system

Bones, muscles, joints, tendons, cartilage, ligaments, and connective tissue.

What are the functions of the musculoskeletal system?

• Support/structure

• movement

• protection of organs

• mineral storage (calcium and phosphorus)

• blood cell production (bone marrow)

• shock absorption and reduces friction during movement

What is the difference between a muscle's origin and insertion?

Origin: typically the more stationary attachment. Insertion: typically the more movable attachment.

How do skeletal muscles produce movement?

1. Sarcomeres shorten → causing the muscle to contract.

2. Muscles pull (never push) → pulling on bones through tendons.

3. Bones move at joints → producing movement through a lever system

In order to produce a movement, a muscle must be attached to two bones and cross at least one joint

What is an agonist vs. antagonist?

Agonist (prime mover): muscle primarily responsible for a movement. (ex: (biceps) contracts and shortens to bend the elbow)

Antagonist: opposes the agonist's movement. (ex: (triceps) relaxes and lengthens to allow the movement)

What is fascia?

Dense irregular connective tissue that covers, separates, or holds together muscles, organs, blood vessels, and nerves.

What is muscle tone?

Slight, continuous contraction of muscles even at rest.

What is an isometric contraction?

Muscle tension increases (sarcomeres shorten bc of increased tension), but overall muscle length does not change.

What is an isotonic contraction?

Muscle changes length (shortens or lengthens) while moving a load.

concentric: tension development while shortening

What is the difference between shunt and spurt muscles?

Shunt: pull parallel to the bone to stabilize a joint. Spurt: pull obliquely to the bone to produce effective movement.

Which muscle contraction is associated with the most injuries?

Isotonic eccentric contractions (Because the muscle lengthens while contracting, creating high tension that can damage or tear muscle fibers)

How are muscles named?

By shape, size, attachments, and functions

What is an aponeurosis?

A wide, flat tendon

What makes up the axial skeleton?

Skull, vertebral column, and thoracic cage

What makes up the appendicular skeleton?

Pectoral (shoulder) girdle, Upper limb, Pelvic girdle, Lower limb

What are the 3 main types of joints?

Fibrous: little/no movement

Cartilaginous: slight movement

Synovial: freely movable

What are fibrous joints (synarthroses)? and what does it have (2 things)

Bones joined by fibrous connective tissue with limited or no movement.

• sutures: Fibrous joints connecting skull bones.

• syndesmosis: Bones joined by dense fibrous connective tissue, such as interosseous ligaments

What are Cartilaginous joints? and what does it have (2 things)

joints where bones are connected by cartilage rather than a joint cavity (little to no movement)

• synchondrosis: Cartilaginous joint connected by hyaline cartilage (flexible tissue), e.g., epiphyseal plate or costochondral joint

• symphysis: Cartilaginous joint connected by fibrocartilage (ex: stable hard to move), e.g., pubic symphysis

What are synovial joints (diarthroses)

freely movable joints that have a fluid-filled joint cavity between the bones

What is synostosis?

Fusion of bones

What are the 2 types of synoviocytes in the synovial membrane?

Type A: macrophage-like (remove debris and waste from the joint) Type B: fibroblast-like (produces components of synovial fluid)

What are the 4 main structures of a synovial joint?

Hyaline articular cartilage covers bone ends; joint cavity contains synovial fluid; fibrous capsule stabilizes the joint; synovial membrane lines the capsule and helps produce synovial fluid.

dermatome

an area of skin innervated by a single spinal nerve

What is the brachial plexus?

A network of nerves from C5–T1 that supplies movement and sensation to the upper limb.

What are the five organizational levels of the brachial plexus?

Roots (5) → Trunks (3) → Divisions (3 anterior and 3 posterior) → Cords (3: lateral, medial, and posterior) → Branches (lot but 5 main ones)

What are the five major terminal branches?

Musculocutaneous, Axillary, Radial, Median, Ulnar (MARMU)

Movements of the Pectoral Girdle

• depression and elevation

• retraction and protraction

Three Main Muscles that move the Pectoral Girdle (Posterior)

Posterior:

• Trapezius (one of the largest muscles on the back, elevates, retracts, depresses, and upwardly rotates scapula)

• Levator scapulae (elevates the scapula (shrugs shoulders) and assists in downward rotation)

• Rhomboids (Retract the scapula (pull shoulder blades together))

Anterior Muscles that move the Pectoral Girdle

Anterior:

• Serratus anterior (Protracts the scapula (pulls shoulder blade forward), upwardly rotates it, and holds it against the rib cage)

• Pectoralis minor (Protracts, depresses, and downwardly rotates the scapula. Innervated by the medial pectoral nerve)

• Subclavius (Depresses and stabilizes the clavicle)

What muscles move the arm and originate from the axial skeleton?

Pectoralis major and latissimus dorsi

What muscles move the arm and originate from the scapula?

Deltoid, coracobrachialis, teres major, triceps brachii, and rotator cuff muscles

What are the actions and innervation of pectoralis major?

Actions: flexion, adduction, rotation of arm

Innervation: pectoral nerves

What are the actions and innervation of latissimus dorsi?

Actions: extension, adduction, rotation of arm

Innervation: thoracodorsal nerve

What are the actions and innervation of deltoid?

Actions: flex, extend, and abduct the arm

Innervation: axillary nerve

What are the actions and innervations of the rotator cuff (what is it composed of)

Composed of: infraspinatus, supraspinatus, subscapularis, and teres minor

• surround shoulder joint: stabilize joint, abduct and rotate arm at shoulder

• innervation: posterior branches of brachial plexus

• all except the supraspinatus rotate the humerus (assists with abduction instead)

What do both the Coracobrachalis and Biceps brachii do and are innervated by what nerve? And what is the Triceps Brachii innervated by?

• Flex

• Musculocutaneous nerve

Triceps: radial

What is the glenohumeral joint and what helps stabilize it?

The shoulder joint between the head of the humerus and glenoid cavity of the scapula

• shallow ball-and-socket joint so it has Rotator cuff muscles and their tendons to help stabilize it

What muscles are in the anterior compartment of the arm, what are their actions, and what nerve innervates it?

Biceps brachii (also supinates!!), brachialis, coracobrachialis

• Actions: Flexion at shoulder/elbow, adduction at shoulder, and supination

• Innervations: Musculocutaneous nerve

What muscle is n the posterior compartment of the arm, what are their actions, and what nerve innervates it?

Triceps brachii

Actions: extension at elbow and shoulder

Innervation: radial nerve

Which muscles flex the arm at the shoulder and Which muscles flex the forearm at the elbow?

1. flex arm at shoulder: Coracobrachialis and biceps brachii

2. flex forearm at elbow: Biceps brachii and brachialis

What are the two bones of the forearm and what connects them?

Radius (lateral) and ulna (medial) connected by Interosseous membrane, a type of fibrous joint called a syndesmosis

What are the actions of the anterior forearm compartment and what nerves innervate them?

Flexes wrist/digits and pronates forearm

• Innervated primarily by Median nerve, but also Ulnar

• Brachioradialis is the exception and is innervated by the Radial nerve

What are the actions of the posterior forearm compartment and what nerves innervate them?

Actions: extension of wrist and digits

Innervation: radial nerve

Carpel Tunnel Syndrome

a medical condition that happens when swelling or pressure squeezes the median nerve inside the rigid passageway made of bones and a tough ligament

What muscles supinate the forearm?

Biceps brachii (musculocutaneous nerve) and supinator (radial nerve)

What muscles pronate the forearm?

Pronator teres and pronator quadratus (median nerve)

What are the 3 groups of intrinsic hand muscles?

Thenar, hypothenar, and midpalmar

What are the functions and innervation of thenar muscles?

Flex, abduct, and oppose thumb. Median nerve

What are the functions and innervation of hypothenar muscles?

Flex, abduct, and oppose 5th digit. Ulnar nerve

What are the functions and innervation of midpalmar muscles

Fine movements of digits. Primarily ulnar nerve

What are the subdivisions and major joints of the lower extremity?

Subdivisions: gluteal region, thigh, leg, foot

Joints: hip, knee, ankle, foot

What 3 bones form the pelvic bone? And where does one of them articulate

Ilium, ischium, and pubis (fused together)

Where does the ilium articulate: With the sacrum; the two pubic bones meet at the pubic symphysis

Why are females pelvis wider than mens

Because it is adapted for childbirth and makes the angle more obtuse for giving birth

What are the major bones of the ankle?

Talus: articulates with tibia

Calcaneus: heel bone, transmits most weight to ground

What are the two arches of the foot and what forms them?

Metatarsals and ankle bones form arches, longitudinal and transverse

What are the main muscles and actions of the gluteal region?

Muscles: gluteus maximus, medius, minimus, tensor fasciae latae

Actions: primarily extension and abduction of thigh

Innervation: gluteal nerves

What is the primary action of gluteus maximus?

Extension of the thigh at the hip

What is the primary action of gluteus medius and minimus?

Abduction of the thigh at the hip

What are the main muscles and actions of the anterior thigh?

Actions: flex thigh at hips

Muscles: Iliopsoas (iliacus + psoas major), sartorius, and rectus femoris

Innervates: femoral nerve (lumbar plexus)

What are the three compartments of the thigh?

Anterior, medial (adductor), and posterior

What are the four muscles of the quadriceps femoris? and what are the actions and innervation of quadriceps femoris?

Rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

Action: extends leg at knee

Innervation: femoral nerve

What are the muscles of the posterior thigh? and what are the actions and innervation of the posterior thigh muscles?

Biceps femoris, semitendinosus, semimembranosus

Actions: extend thigh at hip and flex leg at knee

Innervation: sciatic nerve (largest nerve of the body)

hamstrings!

What muscles are in the medial thigh compartment and what are the actions and innervation

Adductor magnus, longus, brevis, and gracilis

Action: adduction of thigh at hip

Innervation: obturator nerve

What are the two bones of the leg and their locations?

Tibia: medial, weight-bearing, articulates with femur and ankle. Fibula: lateral, mainly muscle attachment and ankle stabilization

What connects the tibia and fibula?

Interosseous membrane (fibrous connective tissue). Unlike the radius and ulna, they have very little movement relative to each other

What are the 3 articulations of the knee joint?

Two femorotibial articulations (lateral and medial) and one femoropatellar articulation

What are the two layers of the knee joint capsule?

External: fibrous layer

Internal: synovial membrane