Moduel 3 Musculoskeletal & Integumentary Systems

How many bones does adult human skeleton have?

The adult human skeleton has 206 bones.

How many bones are children born with?

Children are born with 300-350 bones.

What process turns cartilage into bone?

Ossification.

What connects bones at joints?

Ligaments.

What are the two main parts of the skeleton?

Axial skeleton (central part) and Appendicular skeleton (limbs and girdles).

Name one function of the skeletal system.

Support: The body and protect organs, such as the rib cage protecting the heart and lungs.

Protection: Bones protect vital organs, such as the skull safeguarding the brain and the vertebrae shielding the spinal cord.

Movement: Bones and muscles work together for movement, with tendons connecting muscles to bones to allow actions like walking, breathing, and lifting.

Storage: Bones store fat and minerals like calcium and phosphorus, supporting muscle contraction and blood clotting, with hormones controlling calcium levels.

Blood cell formation: Bones, especially in the marrow, produce red and white blood cells.

What type of bone is dense and smooth?

Compact bone.

What type of bone has a porous structure?

Spongy bone.

What is intramembranous ossification?

The development of bone from fibrous membranes, forming flat bones such as the skull.

What is endochondral ossification?

The formation of bone from hyaline cartilage, responsible for the development of most bones.

What is bone deposition?

When osteoblasts build new bone

What is bone resorption?

When osteoclasts break down bone tissue.

What is bone remodelling?

The process where bone is constantly remodelled, with about 5-7% of bone mass replaced each week.

Four major properties of muscle tissue?

• Contractility: Ability to shorten and produce movement.

• Excitability: Ability to respond to stimuli and produce action potentials.

• Extensibility: Ability to stretch beyond its resting length without damage

• Elasticity: Ability to return to its resting length after stretching.

What is muscle fatigue?

The inability of a muscle to maintain its force of contraction after prolonged activity.

• Inadequate calcium released from the sarcoplasmic reticulum,

• Insufficient oxygen (O2) supply,

• Sepletion of glycogen,

• Build-up of lactic acid.

What systems does the muscular system interact with for movement?

The skeletal system, Nervous system, Cardiovascular system

What is Aerobic Respiration? (Muscle Metabolism)

Muscle tissue receives oxygen from haemoglobin (Hb) and glucose is metabolised to form ATP.

Structure of the skin

1. Epidermis (Outer Layer – First Line of Defence): Made of keratinised stratified squamous epithelium, it forms a protective, waterproof barrier that prevents harmful entry, detects pathogens, regenerates continuously, and provides UV protection and skin colour.

2. Dermis (Middle Layer – 90% of Skin Thickness): Composed of dense connective tissue with papillary and reticular layers, it provides strength and elasticity, contains collagen and elastin, houses sensory receptors, glands, blood vessels, and hair follicles, supporting protection, nourishment, and temperature regulation.

3. Hypodermis (Subcutaneous Layer): Composed of fat and connective tissue, it cushions and insulates the body, stores energy, helps regulate temperature, and supports nerves and blood vessels connecting to deeper tissues.

What are the stages of wound healing?

• Haemostasis;  Blood vessels constrict, and platelets form a clot to stop bleeding.

• Inflammation: White blood cells clear damaged cells and prevent infection, causing swelling, warmth, and redness.

• Proliferation: New tissue forms, and blood vessels supply oxygen and nutrients to the wound.

• Maturation/remodeling: Collagen reorganises, and the wound closes, though it remains weaker than uninjured skin.

What is Creatine phosphate? (Muscle Metabolism)

Excess ATP is stored as creatine phosphate and used to quickly make ATP during contraction; leftover is excreted as creatinine in urine.

What is Anaerobic respiration? (Muscle Metabolism)

Glycogen is the main energy source in muscles, and during intense activity lactic acid can build up, causing a stitch.

Bone Remodelling & Repair:

• Haematoma formation: Blood clot forms at the fracture site.

• Fibrocartilaginous callus formation: New tissue forms, bridging the broken ends.

• Bony callus formation: Spongy bone replaces the cartilage.

• Bone remodelling: Compact bone forms, restoring bone strength and shape.

Long bones (Bone types)

Longer than they are wide, with a shaft and enlarged ends. Primarily compact bone with spongy bone at the ends. — All bones of the limbs (except patella, wrist, and ankle bones)

Flat bones (Bone types)

Thin, flattened, and usually curved, with two layers of compact bone surrounding a layer of spongy bone. — Skull bones, ribs, sternum (breastbone)

Short bones (Bone types)

Cube-shaped, containing mostly spongy bone with an outer layer of compact bone. — Wrist and ankle bones, patella (as a special type of short bone)

Irregular bones (Bone types)

Do not fit into the other categories. Mainly spongy bone with an outer layer of compact bone. — Vertebrae (spinal column)

Osteoblasts (Types of Bone Cells, and Bone Growth and Development)

Bone-forming cells that synthesise and secrete bone matrix. They are responsible for bone growth and mineralisation.

Osteocytes (Types of Bone Cells, and Bone Growth and Development)

Mature bone cells that maintain bone tissue and regulate mineral content. They originate from osteoblasts that have become embedded in the matrix.

Osteoclasts (Types of Bone Cells, and Bone Growth and Development)

Bone-reabsorbing cells that break down bone tissue, playing a key role in bone remodelling and calcium homeostasis.

Osteogenic Cells (Types of Bone Cells, and Bone Growth and Development)

Stem cells found in the periosteum and bone marrow that differentiate into osteoblasts, playing a crucial role in bone repair and growth.

What nutrients and hormones are needed for bone growth and maintenance?

Calcium, phosphorus, magnesium, vitamins D, C, and A; and hormones such as parathyroid hormone, growth hormone, and calcitonin.

Hinge (Joints)

Movement in one direction eg. door hinge, Elbow

Pivot (Joints)

Rotational movement around an axis; eg. Neck (first and second vertebrae)

Ball-and-Socket (Joints)

Greatest range of movement in all directions eg. Shoulder, Hip

Saddle (Joints)

Angular movement with greater range than condyloid eg. Thumb joint

Condyloid (Joints)

Angular movement along two axes eg. Wrist, fingers

Planar (Gliding) (Joints)

Flat surfaces allow gliding movements eg. Carpals in hand, tarsals in foot

Skeletal Muscle (Muscular System)

Single, long, cylindrical, multinucleate cells with striations. Voluntary; attached to bones. Produces movement, maintains posture, stabilises joints, generates heat.

Cardiac Muscle (Muscular System)

Branching chains of cells, single nucleus, striations, and intercalated discs. Involuntary; found only in the heart. Pumps blood to supply oxygen and nutrients throughout the body.

Smooth Muscle (Muscular System)

Single, fusiform, uninucleate cells with no striations. Involuntary; found in walls of hollow organs (e.g., intestines, blood vessels). Controls movement of substances (food, blood, urine) through body systems.

Muscle Functions & Metabolism

• Generating Motion: Skeletal muscles allow movement, quick precise actions, and facial expressions, while smooth and cardiac muscles control circulation and organ function.

• Mainting Posture: Skeletal muscles continuously adjust to maintain posture against gravity, allowing us to stay upright or seated without conscious effort.

• Stabilising Joints: Muscles and tendons stabilise joints, especially less stable ones like the shoulder and knee, and strengthening surrounding muscles is important for rehabilitation.

• Generating heat: Muscle contractions produce heat to help maintain body temperature, with skeletal muscles (about 40% of body mass) contributing significantly.

Skeletal muscle (structure, control & location, function)

Structure: Single, long, cylindrical, multinucleate cells with striations.

Control & Location: Voluntary; attached to bones.

Function: Produces movement, maintains posture, stabilises joints, generates heat.

Cardiac muscle (structure, control & location, function)

Structure: Branching chains of cells, single nucleus, striations, and intercalated discs.

Control & location: Involuntary; found only in the heart.

Function: Pumps blood to supply oxygen and nutrients throughout the body.

Smooth muscle (structure, control & location, function)

Structure: Single, fusiform, uninucleate cells with no striations.

Control & location: Involuntary; found in walls of hollow organs (e.g., intestines, blood vessels).

Function: Controls movement of substances (food, blood, urine) through body systems.

Functions of Diaphragm (Muscles)

Primary muscle of breathing; contracts to allow air into the lungs and relaxes to expel air.

• Clinical Relavance: Important in respiratory conditions like COPD or mechanical ventilation. Weakness can affect breathing.

Functions of Quadriceps & Hamstrings (Lower Limb) (Muscles)

Quadriceps extend the knee; hamstrings flex the knee. Essential for walking, standing, and posture.

• Clinical Relevance: Assessed in rehabilitation, post-surgery, stroke, or arthritis patients.

Functions of Deltoid (Muscles)

Enables shoulder abduction and arm movement.

• Clinical Relevance: Common site for intramuscular injections. Important to avoid injury and ensure proper technique.

Functions of Gastrocnemius & Soleus (Calf Muscles) (Muscles)

Enable plantar flexion of the foot, crucial for walking, running, and standing.

• Clinical Relevance: Monitored in conditions like deep vein thrombosis (DVT) and peripheral arterial disease.

Functions of Biceps & Triceps (Upper Arm) (Muscles)

Biceps flex the elbow; triceps extend the elbow. Essential for arm movement.

• Clinical Relevance: Assessed in neurological exams, stroke recovery, and rehabilitation.

Functions of Erector Spinae (Back Muscles) (Muscles)

Support posture and allow back extension and rotation.

• Clinical Relevance: Monitored in back pain, spinal injuries, and postural issues like scoliosis.

Functions of Abdominal Muscles (Rectus Abdominis, Obliques) (Muscles)

Support trunk stability, assist in breathing, and allow twisting/bending movements.

• Clinical Relevance: Assessed for core strength, post-surgical recovery, and conditions like hernias.

Functions of Masseter (Muscles)

Primary muscle for chewing.

• Clinical Relevance: Important in assessing TMJ dysfunction, eating difficulties, and dental issues.

Functions of Flexor & Extensor Muscles of the Forearm (Muscles)

Control hand and finger movements.

• Clinical Relevance: Assessed in stroke recovery, carpal tunnel syndrome, and spinal cord injuries.

Functions of Cardiac Muscle (Heart) (Muscles)

Pumps blood throughout the body, supplying oxygen and nutrients.

• Clinical Relevance: Essential in cardiovascular assessment, monitoring heart rate and rhythm in diseases like heart failure.

Functions of Vastus Lateralis (Muscles)

Part of the quadriceps; extends the knee.

• Clinical Relevance: Common site for intramuscular injections, particularly in infants and children. Offers a large, safe area for injection.

Functions of Ventrogluteal (Muscles)

Located on the hip, used for abduction and rotation of the leg.

• Clinical Relevance: Preferred site for intramuscular injections, especially for adults. Safer than the dorsogluteal site and avoids major nerves and blood vessels.

First Line of Defence & Protection (Functions of skin)

• Acts as a mechanical barrier, preventing pathogen entry.

• Keratin and sebum create a waterproof, antimicrobial surface.

• Dendritic cells and macrophages in the skin detect pathogens and help activate the immune response.

• Melanin shields against UV radiation.

• Facilitates wound healing and rapid cell renewal to maintain skin integrity.

Sensation (Functions of skin)

• Contains sensory receptors that detect pain, temperature, and pressure.

• Aids in protective reflexes such as withdrawing from heat.

Thermoregulation (Functions of skin)

• Blood vessel dilation/constriction regulates heat loss or retention.

• Sweating cools the body through evaporation.

• Hair adjusts insulation based on environmental conditions.

Secretion & Absorption (Functions of skin)

• Eliminates waste products (water, sodium, CO₂, ammonia, urea) via sweat glands.

• Absorbs fat-soluble substances, like certain medications (e.g., transdermal patches), toxins, and vitamins.

• Excess sweating can lead to dehydration and hyponatraemia.

Vitamin D Synthesis (Functions of skin)

• UV exposure triggers vitamin D production, which is further processed by the liver and kidneys.

Vital for

○ Bone mineralisation (calcium absorption)
○ Immune function
○ Prevention of cardiovascular disease, diabetes, and cancer
○ Regulation of hair follicle cycles and tumour suppression.