GW BGZ 2025 Case 1 - At the fitness center

What are the main types of bones based on shape?

here are six major bone types:

1. Long bones (Ossa longa)

   • Longer than they are wide.

   • Function as levers for movement.

   • Examples: femur, humerus, tibia.

2. Short bones (Ossa brevia)

   • Roughly cube-shaped.

   • Provide stability with limited movement.

   • Examples: carpals (wrist), tarsals (ankle).

3. Flat bones (Ossa plana)

   • Thin, flattened, often curved.

   • Protect organs and provide muscle attachment.

   • Examples: ribs, sternum, scapula, skull bones.

4. Irregular bones (Ossa irregularia)

   • Complex shapes that do not fit other categories.

   • Examples: vertebrae, mandible.

5. Sesamoid bones (Ossa sesamoidea)

   • Embedded within tendons.

   • Reduce friction and improve leverage.

   • Examples: patella, pisiform.

6. Pneumatic bones (Ossa pneumatica)

   • Contain air-filled spaces (sinuses).

   • Examples: frontal bone, ethmoid bone, sphenoid bone, maxilla, temporal bone.

What is laminar bone?

Laminar bone refers to mature bone tissue organized into layers called lamellae.

Characteristics:

• Found in compact bone.

• Provides strength and resistance to stress.

• Represents the normal mature organization of bone tissue.

What are the names of the bones in the body and where are they? (the “bigger” bones)?

Bone / Bone Group	Location in the Body
Cranium	Upper part of the skull; protects the brain
Facial bones	Front of the skull; form the face
Clavicle	Collarbone; between the breastbone and shoulder
Scapula	Shoulder blade; upper back
Sternum	Breastbone; center of the chest
Ribs	Surround the chest and protect the heart and lungs
Vertebrae	Individual bones of the spine
Vertebral column	Entire backbone/spine running from neck to pelvis
Sacrum	Triangular bone at the base of the spine, between the hips
Humerus	Upper arm bone (shoulder to elbow)
Radius	Forearm bone on the thumb side
Ulna	Forearm bone on the little-finger side
Carpals	Wrist bones
Metacarpals	Bones of the palm of the hand
Phalanges (hand)	Finger bones
Femur	Thigh bone; hip to knee
Patella	Kneecap
Tibia	Shinbone; larger lower-leg bone
Fibula	Smaller lower-leg bone, beside the tibia
Tarsals	Ankle bones
Metatarsals	Middle bones of the foot
Phalanges (foot)	Toe bones

What is bone and what are its main functions?

Bone is a specialized connective tissue that forms the skeleton. Although bone appears hard and lifeless, it is actually a living tissue containing cells, blood vessels, nerves, and an extracellular matrix.

Bone performs several important functions:

1. Support

Bones provide the structural framework of the body and support all soft tissues and organs.

2. Protection

Bones protect vital organs:

• Skull protects the brain.

• Vertebral column protects the spinal cord.

• Rib cage protects the heart and lungs.

3. Movement

Bones act as levers for muscles. When muscles contract, they pull on bones, producing movement at joints.

4. Mineral Storage

Bones store important minerals:

• Calcium

• Phosphate

These minerals can be released into the bloodstream when needed.

5. Blood Cell Production

Red bone marrow produces:

• Red blood cells

• White blood cells

• Platelets

This process is called hematopoiesis.

6. Fat Storage

Yellow bone marrow stores energy in the form of fat.

What are the major parts of a long bone?

A typical long bone consists of several important structures:

Diaphysis

• The shaft or long central portion of the bone.

• Mainly composed of compact bone.

• Contains the medullary cavity.

Epiphyses

• The enlarged ends of the bone.

• Mainly composed of spongy bone covered by a thin layer of compact bone.

Metaphysis

• Transition region between the diaphysis and epiphysis.

• Contains the growth plate in children.

Periosteum

• Tough outer connective tissue covering.

• Contains blood vessels and nerves.

Endosteum

• Thin membrane lining internal bone surfaces.

Medullary Cavity

• Hollow cavity inside the diaphysis.

• Contains bone marrow.

Together these structures allow bones to grow, repair themselves, and withstand mechanical stress.

What is the diaphysis and what is its function?

The diaphysis is the shaft or long central portion of a long bone.

Characteristics:

• Composed mainly of compact bone.

• Surrounds the medullary cavity.

• Provides strength and rigidity.

Functions:

• Supports body weight.

• Resists bending forces.

• Provides attachment sites for muscles.

Examples:

• The shaft of the femur.

• The shaft of the humerus.

Because compact bone is very dense, the diaphysis is extremely strong and well suited for weight-bearing activities.

What are the epiphyses and what is their function?

The epiphyses are the enlarged ends of a long bone.

Characteristics:

• Mostly composed of spongy bone.

• Covered by a thin layer of compact bone.

• Covered by articular cartilage where joints form.

Functions:

• Form joints with neighboring bones.

• Distribute forces across joints.

• Reduce bone weight while maintaining strength.

The spongy bone inside the epiphyses contains trabeculae arranged along lines of stress, making the bone strong without being excessively heavy.

What is the metaphysis and why is it important?

The metaphysis is the region between the diaphysis and epiphysis.

In children and adolescents:

• Contains the epiphyseal (growth) plate.

• Bone length increases here.

In adults:

• The growth plate closes.

• It becomes the epiphyseal line.

Importance:

• Responsible for longitudinal bone growth.

• Site of active bone remodeling during development.

Without the metaphysis and growth plate, bones could not increase in length during childhood.

What is the epiphyseal plate and how does bone growth occur?

The epiphyseal plate, also called the growth plate, is a layer of hyaline cartilage found within the metaphysis of growing bones.

During childhood:

• Cartilage cells divide rapidly.

• New cartilage is produced.

• Osteoblasts replace cartilage with bone tissue.

This process causes bones to become longer.

When growth ends:

• Cartilage is completely replaced by bone.

• The plate ossifies.

• An epiphyseal line remains.

The closure of growth plates marks the end of height increase.

What is the periosteum and what are its functions?

The periosteum is a dense connective tissue membrane covering the external surface of bone, except where articular cartilage is present.

It contains:

• Blood vessels

• Nerves

• Osteoblasts

• Osteoclasts

Functions:

Protection

Protects underlying bone tissue.

Blood Supply

Provides nutrients and oxygen.

Muscle Attachment

Serves as an attachment point for tendons and ligaments.

Growth and Repair

Contains bone-forming cells important for healing fractures.

The periosteum is firmly attached to bone by Sharpey's fibers (perforating fibers).

What is red bone marrow and what does it do?

Red bone marrow is specialized tissue responsible for blood cell production.

Produces:

• Red blood cells (erythrocytes)

• White blood cells (leukocytes)

• Platelets (thrombocytes)

This process is called hematopoiesis.

In adults, red marrow is found mainly in:

• Vertebrae

• Ribs

• Sternum

• Pelvis

• Proximal ends of long bones

What is yellow bone marrow?

Yellow bone marrow consists mainly of adipose (fat) tissue.

Functions:

• Energy storage.

• Fat reserve.

In severe blood loss, yellow marrow can convert back into red marrow to increase blood cell production.

What is the endosteum?

The endosteum is a thin connective tissue membrane lining all internal bone surfaces.

It covers:

• Medullary cavity

• Trabeculae of spongy bone

• Central canals

Functions:

• Bone growth

• Bone repair

• Bone remodeling

Contains:

• Osteoblasts

• Osteoclasts

These cells constantly maintain bone tissue throughout life.

What is compact bone?

Compact bone is the dense outer layer of bone tissue.

Characteristics:

• Strong

• Heavy

• Highly organized

Functions:

• Provides strength.

• Resists bending.

• Protects internal bone structures.

Compact bone is especially abundant in the diaphysis of long bones.

What is spongy bone?

Spongy bone, also called cancellous bone, is a lightweight network of bony plates called trabeculae.

Characteristics:

• Porous appearance.

• Contains marrow spaces.

• Lacks osteons.

Functions:

• Reduces skeletal weight.

• Absorbs stress.

• Houses bone marrow.

Spongy bone is found mainly in:

• Epiphyses

• Vertebrae

• Flat bones

What are trabeculae?

Trabeculae are thin bony plates that form the structural framework of spongy bone.

Characteristics:

• Arranged along stress lines.

• Contain osteocytes.

• Surrounded by bone marrow.

Functions:

• Provide strength with minimal weight.

• Distribute forces efficiently.

• Resist compression.

The arrangement of trabeculae changes according to mechanical stresses placed on the bone.

What are osteoblasts, osteocytes, and osteoclasts?

Osteoblasts

Bone-forming cells.

Functions:

• Produce osteoid.

• Deposit bone matrix.

• Build new bone.

Osteocytes

Mature bone cells.

Functions:

• Maintain bone tissue.

• Monitor bone stress.

• Coordinate remodeling.

Osteoclasts

Bone-resorbing cells.

Functions:

• Break down bone matrix.

• Release minerals into blood.

• Participate in remodeling.

Bone health depends on a balance between osteoblast and osteoclast activity.

What is skeletal muscle, what are muscle fibers, and what are the main functions of skeletal muscle?

Skeletal muscle is one of the three muscle types in the body and is responsible for voluntary movement, meaning it is under conscious control. Skeletal muscles attach to bones through tendons and produce movement by pulling on the skeleton when they contract.

The basic cell of skeletal muscle is called a muscle fiber (or myocyte). Muscle fibers are very long, cylindrical cells that contain many nuclei. Unlike most cells, muscle fibers are specialized for contraction and contain numerous contractile structures called myofibrils.

The main functions of skeletal muscle are:

• Producing body movement

• Maintaining posture and body position

• Stabilizing joints

• Supporting soft tissues

• Generating heat during contraction

• Assisting breathing and circulation through muscle activity

Each muscle is made of thousands of muscle fibers organized into bundles called fascicles.

Describe the complete structure of skeletal muscle from the whole muscle down to the contractile proteins.

Skeletal muscle has several levels of organization:

Whole muscle

• Surrounded by connective tissue called the epimysium

Fascicle

• Bundle of muscle fibers

• Surrounded by perimysium

Muscle fiber (muscle cell)

• Surrounded by endomysium

• Covered by the cell membrane called the sarcolemma

• Filled with cytoplasm called the sarcoplasm

Inside each muscle fiber are:

Myofibrils

• Long contractile structures running through the fiber

Each myofibril consists of repeating units called:

Sarcomeres

• Basic contractile units of muscle

Within each sarcomere are:

Thin filaments

• Made of actin

Thick filaments

• Made of myosin

When actin and myosin interact, muscle contraction occurs.

What are the connective tissue layers of skeletal muscle and what are their functions?

Three connective tissue layers organize and support skeletal muscle:

Endomysium

• Surrounds each individual muscle fiber

• Contains small blood vessels and nerves

• Helps support individual muscle cells

Perimysium

• Surrounds bundles of fibers called fascicles

• Provides structural organization

• Contains larger blood vessels and nerves

Epimysium

• Surrounds the entire muscle

• Protects the muscle

• Merges with tendons that attach muscle to bone

Together these layers help distribute force generated during contraction and provide protection and organization.

What is a sarcomere and what are its major parts?

The sarcomere is the basic contractile unit of skeletal muscle and is responsible for producing force and movement.

A sarcomere extends from one Z-line to the next.

Important structures include:

Z-line (Z-disc)

• Marks the boundaries of a sarcomere

• Anchors actin filaments

I-band

• Light-colored region

• Contains only actin filaments

A-band

• Dark region

• Contains the entire length of myosin filaments

• Includes areas where actin overlaps with myosin

H-zone

• Central region of the A-band

• Contains only myosin filaments

These structures work together to allow muscle contraction through filament sliding.

Explain the sliding filament theory of muscle contraction and describe what happens to the sarcomere during contraction.

The sliding filament theory explains how muscles contract.

During contraction:

1. Calcium is released from the sarcoplasmic reticulum.

2. Myosin heads bind to actin filaments.

3. Myosin pulls actin toward the center of the sarcomere.

4. Actin slides over myosin.

5. The sarcomere shortens.

Importantly:

• Actin filaments do not shorten.

• Myosin filaments do not shorten.

• Only the amount of overlap changes.

Changes during contraction:

• Z-lines move closer together.

• I-band becomes smaller.

• H-zone becomes smaller or disappears.

• A-band remains the same size.

The shortening of millions of sarcomeres produces whole-muscle contraction.

What are the different muscle fiber types and how do they differ?

Muscle fibers are classified according to contraction speed, fatigue resistance, and energy production.

Type I fibers (Slow-twitch)

Characteristics:

• Slow contraction speed

• Red appearance due to high myoglobin content

• Many mitochondria

• Aerobic metabolism

• Highly fatigue resistant

Functions:

• Standing

• Walking

• Posture maintenance

• Long-distance running

• Endurance activities

Additional feature:

• Thicker Z-lines

• Better structural integrity

• Less likely to be damaged

Type IIa fibers

Characteristics:

• Intermediate fibers

• Mix of aerobic and anaerobic metabolism

• Moderate fatigue resistance

Functions:

• Middle-distance activities

• Repeated moderate-intensity effort

Type IIx fibers

Characteristics:

• Fastest contraction speed

• White appearance

• Few mitochondria

• Anaerobic metabolism

• Fatigue quickly

Functions:

• Sprinting

• Jumping

• Heavy lifting

• Explosive movements

Generate the greatest force and power.

What important supporting structures are found inside muscle fibers and what are their functions?

Several structures support muscle contraction and energy production.

Glycogen

• Stores glucose

• Provides energy for contraction

Myoglobin

• Stores oxygen

• Gives muscle a red color

Mitochondria

• Produce ATP

• Essential for muscle contraction

Sarcoplasmic reticulum

• Stores calcium

• Releases calcium to initiate contraction

T-tubules

• Conduct electrical signals into the muscle fiber

• Ensure synchronized contraction

Together these structures provide energy, oxygen, and signaling necessary for muscle function.

What are the names of the muscles in the body and where are they?

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What are fascicles and how does fascicle arrangement affect muscle function?

A fascicle is a bundle of muscle fibers surrounded by perimysium.

The arrangement of fascicles determines:

• Force production

• Range of motion

• Direction of pull

• Overall muscle function

Different muscles have different fascicle arrangements depending on the job they perform.

Parallel muscles favor movement.

Pennate muscles favor force production.

Convergent muscles allow versatile pulling directions.

Circular muscles control openings.

Describe all major fascicle arrangements, their characteristics, and examples.

Parallel

Characteristics:

• Fibers run parallel to muscle length

• Large range of motion

• Lower force production

Example: sartorius

Fusiform

Characteristics:

• Spindle-shaped

• Thick middle and narrow ends

• Good range of motion

• Moderate force

Example:biceps brachii

Convergent

Characteristics:

• Broad origin

• Fibers converge into one tendon

• Can pull in different directions

Example: pectoralis major

Unipennate

Characteristics:

• Fibers attach to one side of tendon

• High force production

Example: extensor digitorum longus

Bipennate

Characteristics:

• Fibers attach on both sides of tendon

Example: rectus femoris

Multipennate

Characteristics:

• Fibers attach from many directions

• Greatest force production

Example: deltoid

Circular

Characteristics:

• Fibers arranged in rings

• Open and close body openings

Examples: orbicularis oculi

How are muscles attached to bones and how can muscle attachments help predict movement?

Skeletal muscles attach to bones through tendons.

Each muscle generally has:

Origin

• Less movable attachment

• Usually proximal

• Acts as the fixed point

Insertion

• More movable attachment

• Usually distal

• Moves toward the origin during contraction

A muscle's action can often be predicted by:

1. The bones it attaches to

2. The joint it crosses

3. Its position relative to the joint

General rules:

• Crossing the front of a joint usually causes flexion.

• Crossing the back of a joint usually causes extension.

Examples:

Biceps brachii

Origin: scapula

Insertion: radius

Action: elbow flexion and forearm supination

What are agonists, antagonists, synergists, and fixators?

Muscles rarely work alone.

Agonist (Prime mover)

The main muscle responsible for producing a movement.

Example:

• Biceps during elbow flexion.

Antagonist

Produces the opposite action and relaxes while the agonist contracts.

Example:

• Triceps during elbow flexion.

Synergist

Assists the agonist and helps produce smooth movement.

Example:

• Brachialis assisting the biceps.

Fixator

Stabilizes the origin of the agonist.

Example:

• Muscles stabilizing the scapula during arm movement.

These muscle relationships allow coordinated and efficient movement.

What is a joint (articulation) and what is its overall purpose in the body?

A joint, also called an articulation, is a location in the body where two or more bones meet. Joints are essential because they provide both stability and movement for the skeleton.

Their two main functions are:

1. To hold bones together securely

   • Joints maintain the structural integrity of the skeleton and keep bones aligned.

2. To allow movement

   • Depending on the joint type, they can allow no movement, slight movement, or free movement.

Joints range from completely immovable structures in the skull to highly mobile joints like the shoulder and hip. The type of joint determines how much motion is possible and in what directions.

What are the functional classifications of joints and what movements do they allow?

Joints are classified functionally based on how much movement they allow:

Synarthroses (immovable joints)

• Allow no movement

• Designed for protection and stability

• Example: skull sutures

These joints are important for protecting delicate structures like the brain.

Amphiarthroses (slightly movable joints)

• Allow limited movement

• Provide both stability and flexibility

• Example: intervertebral discs, pubic symphysis

These joints absorb shock and allow slight flexibility in the spine and pelvis.

Diarthroses (freely movable joints)

• Allow wide range of movement

• Found mainly in limbs

• Example: shoulder, hip, elbow, knee

These are the most common functional joints for movement in daily life.

What are false and true joints?

rue joints (movable joints)

• These are joints where movement is possible

• Bones are connected by cartilage and/or a joint capsule

• They allow different types of motion (bend, rotate, slide)

Examples:

• Knee joint

• Shoulder joint

• Elbow joint

• Hip joint

These are the normal “functional” joints in the body.

False joints (immovable joints)

• These joints allow no movement or very little movement

• Bones are tightly connected by fibrous tissue

• They are mostly found in the skull

Example:

• Sutures between skull bones (like between frontal and parietal bones)

These are important for protection of the brain and keeping the skull rigid.

What are the structural classifications of joints and how do they differ in movement?

Joints are also classified structurally based on what connects the bones:

Fibrous joints

• Bones connected by dense connective tissue

• Usually immovable

• Examples:

  • Skull sutures (no movement)

  • Gomphoses (teeth in sockets)

  • Syndesmoses (slight movement, e.g., tibia-fibula)

These joints prioritize stability over movement.

Cartilaginous joints

• Bones connected by cartilage

• Allow limited movement

• Two types:

  • Synchondroses (hyaline cartilage, usually immovable)

  • Symphyses (fibrocartilage, slightly movable)

Examples:

• Intervertebral discs (slight movement + shock absorption)

• Pubic symphysis

These joints balance movement and shock absorption.

Synovial joints

• Bones separated by a fluid-filled cavity

• Freely movable joints

• Most joints in limbs are synovial

These are the most important joints for body movement.

What is the structure of a synovial joint and how does it function?

Synovial joints are highly movable joints with a complex structure designed for smooth motion.

Key structures: Articular cartilage

• Smooth hyaline cartilage covering bone ends

• Reduces friction and absorbs shock

• Has no direct blood supply

Synovial membrane

• Inner lining of joint capsule

• Rich in blood supply

• Produces synovial fluid

Synovial fluid

• Thick lubricating fluid inside joint cavity

• Reduces friction during movement

• Provides nutrients to articular cartilage

Joint cavity

• Space between bones filled with synovial fluid

Fibrous capsule

• Tough outer layer that encloses joint

Ligaments

• Connect bone to bone

• Provide stability and prevent dislocation

What are the types of synovial joints and what movements do they allow?

Plane joints

• Flat surfaces slide over each other

• Movement: gliding only (nonaxial)

• Example: wrist bones, vertebrae

Hinge joints

• One bone fits into a trough-like structure

• Movement: flexion and extension only

• Uniaxial

• Examples: elbow, knee, fingers

Pivot joints

• One bone rotates inside a ring

• Movement: rotation only

• Uniaxial

• Examples: atlas-axis joint (neck), radioulnar joint

Condyloid (ellipsoid) joints

• Oval-shaped surfaces

• Movement: flexion, extension, abduction, adduction

• Biaxial

• Example: knuckles, wrist

Saddle joints

• Both bones have concave and convex surfaces

• Movement: biaxial, wide range

• Example: thumb joint

• Allows opposition (thumb movement)

Ball-and-socket joints

• Spherical head fits into socket

• Movement: all directions + rotation

• Multiaxial

• Examples: shoulder, hip

What are the main types of movement produced at joints?

Flexion

• Decreases joint angle

• Brings body parts closer together

• Example: bending elbow or knee

Extension

• Increases joint angle

• Straightens body part

• Example: straightening arm or leg

Abduction

• Movement away from midline

• Example: raising arms sideways

Adduction

• Movement toward midline

• Example: bringing arms back down

Rotation

• Bone turns around its long axis

• Example: turning head side to side

Circumduction

• Combination of flexion, extension, abduction, adduction

• Circular movement

• Example: arm circles

What are special movements of the body and where do they occur?

Dorsiflexion

• Lifting foot upward toward shin

• Occurs at ankle

Plantar flexion

• Pointing toes downward

• Like pressing a gas pedal

Inversion

• Sole turns inward (medially)

Eversion

• Sole turns outward (laterally)

Supination

• Palm faces upward/anteriorly

• Radius and ulna parallel

Pronation

• Palm faces downward/posteriorly

• Radius crosses over ulna

Opposition

• Thumb touches fingertips

• Essential for grasping objects

Elevation / Depression

• Elevation: movement upward (shoulders shrug)

• Depression: movement downward

Protraction / Retraction

• Protraction: forward movement (jaw, shoulders)

• Retraction: backward movement

What are the movements of muscles?

Concentric contraction

• Muscle shortens while generating force

• Movement occurs because the muscle pulls the insertion toward the origin

• Produces visible motion at the joint

• Example:

  • lifting a dumbbell during a biceps curl (elbow flexion)

Eccentric contraction

• Muscle lengthens while still producing force

• Happens when the muscle is actively resisting a load

• Controls or slows movement rather than creating it

• Example:

  • lowering a dumbbell slowly during a biceps curl

Isometric contraction

• Muscle produces force without changing length

• No joint movement occurs, but tension is generated

• Used for stabilization and posture

• Example:

  • holding a weight still at 90° elbow flexion

  • maintaining posture while standing

What are the axes and planes of movement?

Main axes of the body

• Sagittal axis

  • Runs front to back

  • Perpendicular to frontal plane

  • Mainly involved in abduction/adduction movements

• Transverse axis

  • Runs left to right

  • Perpendicular to sagittal plane

  • Mainly involved in flexion/extension movements

• Longitudinal (vertical) axis

  • Runs top to bottom

  • Perpendicular to transverse plane

  • Mainly involved in rotation movements

Main anatomical planes

• Median (mid-sagittal) plane

  • Divides body into equal left and right halves

• Sagittal plane

  • Any plane parallel to median plane

  • Divides body into left and right portions

• Frontal (coronal) plane

  • Divides body into anterior (front) and posterior (back) sections

• Transverse (horizontal/axial) plane

  • Divides body into upper and lower parts

Key idea:

Movement happens in a plane and rotates around a perpendicular axis.

During elbow flexion, the biceps brachii acts as a primary agonist (along with the brachialis), while the triceps brachii functions as the main antagonist. Synergists that assist the biceps brachii include the brachialis and brachioradialis.

During knee flexion, the hamstrings act as the primary movers (agonists) to bend the knee. The quadriceps femoris act as the antagonists, relaxing to allow bending or resisting to control the speed. Synergists that assist with flexion include the gastrocnemius, popliteus, gracilis, and sartorius.