Anatomy and Physiology of Bones, Joints, and Muscles

What are the five types of bones?

Long bones (e.g., femur), short bones (e.g., carpals), flat bones (e.g., sternum), irregular bones (e.g., vertebrae), and sesamoid bones (e.g., patella).

What are the three main parts of a long bone?

Epiphysis (ends with spongy bone and red marrow), diaphysis (shaft with compact bone and yellow marrow), and metaphysis (transition area with epiphyseal plate).

What is the function of red marrow?

Produces blood cells (hematopoiesis) and is found in flat bones and the epiphyses of long bones.

What is the periosteum?

The outer layer of bone that contains blood vessels, nerves, and osteoblasts.

What is the difference between compact bone and spongy bone?

Compact bone is dense and forms the outer layer, while spongy bone is lighter, porous, and made of trabeculae.

What are osteons?

Structural units of compact bone that consist of lamellae, lacunae, canaliculi, and a central canal.

What is the role of osteoblasts?

Build bone matrix and are responsible for bone formation.

What is osteoporosis?

A condition characterized by loss of bone mass, leading to brittle and porous bones, often due to aging and low estrogen levels.

What are the four stages of fracture healing?

1. Hematoma formation, 2. Fibrocartilaginous callus formation, 3. Bony callus formation, 4. Bone remodeling.

What is a joint?

An articulation where two or more bones meet, allowing for movement and/or stability.

What are fibrous joints?

Lack a synovial cavity

• Bones held closely together by

fibrous connective tissue

• Presence of dense connective tissue,

as well as collagen.

• Little or no movement

(synarthroses or amphiarthroses)

(e.g., sutures in the skull).

What are synovial joints?

Freely movable joints with a fluid-filled cavity, characterized by features like articular cartilage, synovial fluid, and ligaments.

What is synovial fluid?

A thick, slippery fluid in the joint cavity that lubricates joints, absorbs shock, transports nutrients, and removes waste.

What is articular cartilage?

A smooth layer of hyaline cartilage covering the ends of bones at synovial joints, reducing friction and absorbing shock.

What is the function of osteoclasts?

Break down bone tissue (resorption) to release calcium into the bloodstream.

What is interstitial growth in bones?

Length growth at epiphyseal plates where cartilage expands and is ossified into bone.

What is appositional growth in bones?

Width growth that continues throughout life, where osteoblasts add bone to the outer surface.

What is a greenstick fracture?

An incomplete break in a bone, commonly seen in children.

What is a comminuted fracture?

A fracture where the bone shatters into multiple pieces.

What is the role of calcium in bone health?

Calcium is essential for bone strength; osteoblasts store calcium in bones while osteoclasts release it into the bloodstream.

What are the causes of osteoporosis?

Aging, especially in postmenopausal women due to decreased estrogen, poor calcium/vitamin D intake, and lack of weight-bearing exercise.

What is the function of articular cartilage?

Distributes load and spreads out pressure across the joint to avoid damage.

What does 'avascular' mean in relation to articular cartilage?

It has no blood vessels and relies on synovial fluid for nutrients.

What condition can damage articular cartilage and cause pain?

Osteoarthritis can cause pain, stiffness, and reduced mobility.

What type of joint is characterized by gliding movements?

Plane (gliding) joints, such as intercarpal joints in the wrist.

What type of joint allows for flexion and extension?

Hinge joints, such as the elbow and knee.

What is a pivot joint and give an example?

A joint that allows rotation, such as the atlas/axis (C1-C2) joint.

What type of joint allows all angular movements except rotation?

Condyloid (ellipsoid) joints, such as the wrist joint.

What is the functional classification of a joint that is immovable?

Synarthrosis, which includes fibrous and some cartilaginous joints.

What is the example of a synarthrosis joint?

Skull sutures or teeth in sockets (gomphosis).

What type of joint is slightly movable?

Amphiarthrosis, such as intervertebral discs.

What is the freely movable joint classification?

Diarthrosis, which includes synovial joints like the shoulder and knee.

What is flexion in terms of joint movement?

Decreases the angle between two bones, like bending the elbow.

What is the difference between isotonic and isometric contractions?

Isotonic contractions change length with tension, while isometric contractions maintain tension without length change.

What is the role of calcium in muscle contraction?

Calcium binds to troponin, moving tropomyosin off actin binding sites to allow contraction.

What is rigor mortis?

A condition after death where myosin heads remain bound to actin due to lack of ATP, causing muscle stiffness.

What are the three types of muscle tissue?

Skeletal (voluntary), cardiac (involuntary), and smooth (involuntary).

What is the function of tendons?

Connect muscles to bones.

What is the primary energy source for muscle contraction?

ATP is required for muscle contraction and relaxation.

What is muscle hypertrophy?

An increase in the diameter of muscle fibers due to forceful, repetitive activity.

What causes muscle atrophy?

Causes include disuse atrophy from lack of activity and denervation atrophy from nerve damage.

What is the sliding filament theory?

1.Calcium binds to troponin → moves tropomyosin off actin binding sites
2. ATP Hydrolysis: Cock myosin head (hydrolysis)
3. Myosin heads bind to actin → cross-bridge forms
4. Power Stroke
5. ATP is required to:
o Release the cross-bridge
o Pump Ca²⁺ back into SR (relaxation

What is the difference between concentric and eccentric contractions?

Concentric contractions shorten the muscle to produce force and movement , while eccentric contractions lengthen it while maintaining force and movement

What is the role of titin in muscle fibers?

Titin anchors thick filaments to the Z disc and provides recoil and stability to the sarcomere.

What is the definition of muscle fatigue?

The inability to contract after prolonged use, often due to low ATP and ion imbalance.

what is an Impacted fracture?

One bone end is driven into another

what is a potts fracture

Fracture in distal fibula (ankle)

what is a Colles’ fracture?

Fracture of distal radius (wrist)

what is a Cartilaginous Joint?

Structure: Bones connected by cartilage

• Mobility: Slightly movable (amphiarthrotic) or immovable

• Types:

• Synchondrosis – bones joined by hyaline cartilage

• Example: epiphyseal plate in growing bones, rib 1 to sternum

• Symphysis – bones joined by fibrocartilage

• Example: pubic symphysis, intervertebral discs

what is a Sarcolemma

Muscle fiber membrane

what is a sarcoplasm

cytoplasm

Myofibrils

Contain sarcomeres (contractile units)

what is a sarcomere structure?

Z Disc

I Band

A Band
H Zone
M Line

what is a z disc

Ends of a sarcomere, anchor actin

what is a I band

Light band (only thin filaments) (near Z disc on both sides

what is a A band

Dark band (full thick filaments) , also has overlap region, where thin and thick filament overlap.

what is an H zone ?

Middle of A band (only thick filaments)

what is a M Line?

Center of sarcomere, holds thick filaments

what are the three types of filaments?

thin, thick, and titin

what is a thin filament made of?

actin

what is a thick filiament made of

Myosin (with heads for cross-bridging)

what is the contraction cycle?

1. ATP hydrolysis → myosin head cocks

2. Myosin binds to actin → power stroke

3. ATP binds to myosin → detachment from actin

4. Continues as long as Ca²⁺ and ATP are present

what are the factors that affect muscle contraction?

• ATP & Ca²⁺ availability

• Temperature & pH

• Nervous input

• Fatigue or disease

what are the energy sources for contraction?

Creatine Phosphate, Anaerobic Glycolysis, and Aerobic Respiration

Creatine Phosphate

immediate, short burst (10–15 sec)

Anaerobic Glycolysis

no O₂, lactic acid byproduct

Aerobic Respiration

O₂ required, efficient, long-term energy

Twitch

Single contraction-relaxation cycle

summation

Increased force with repeated stimul

Incomplete Tetanus

Partial relaxation between multiple stimuli

Complete Tetanus

No relaxation, sustained contraction (multiple stimuli)

Myogram:

Graph of muscle response

spasm

Involuntary contraction of a single muscle

Cramp:

Painful muscle spasm

Tic

Involuntary twitch of voluntary muscle (e.g., eyelid)

 Tremor:

Rhythmic contraction of opposing muscle groups

Fasciculation:

Brief, visible twitch of motor unit under skin