Moduel 3 Musculoskeletal & Integumentary Systems

:Module 3: 

Musculoskeletal & Integumentary Systems


The Skeletal System

- Adult human skeleton has 206 bones

- Children are born with 300–350 bones

- Many bones in children are made of cartilage

- Through ossification, cartilage turns into bone

- As the body grows, bones fuse together, This results in the 206 bones in adults


- Skeleton includes bones, joints, cartilage, and ligaments

- Ligaments connect bones at joints

- Two main parts:

- Axial skeleton – central part of the body

- Appendicular skeleton – limbs and girdles

- Joints provide flexibility and movement



Functions of the Skeletal System

Support: Bones provide the framework that supports the body and protects soft organs, such as the rib cage shielding 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, which support functions such as muscle contraction and blood clotting, with hormones controlling calcium levels between bones and blood. 

Blood cell formation: Bones, particularly those in the marrow, are responsible for producing blood cells, ensuring a constant supply of red and white blood cells.


Classification of Bones:

  • Compact bone is dense, smooth, and uniform in appearance.

  • Spongy bone has a porous, spiky structure, resembling a sponge

 





Types of Bone Cells, and Bone Growth and Development

Bone Growth & Development: Ossification (osteogenesis), begins around six weeks after fertilisation and continues until approximately age 25.

  • Intramembranous ossification – The development of bone from fibrous membranes, forming flat bones such as the skull, mandible, and clavicles.

  • Endochondral ossification – The formation of bone from hyaline cartilage, responsible for the development of most bones in the body, including long bones.

- Long bones grow in length at the epiphyseal (growth) plate and in thickness through appositional growth, with growth plates closing around 18 in females and 21 in males, ending length growth while bones can still thicken throughout life.


Bone Remodelling & Repair: Bone is a dynamic tissue that is constantly remodelled, with about 5–7% of bone mass replaced each week.

  • Bone deposition by osteoblasts, which build new bone.

  • Bone resorption by osteoclasts, which break down bone tissue


  • 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.


Bone growth and maintenance require nutrients like calcium, phosphorus, magnesium, and vitamins D, C, and A, along with hormones such as parathyroid hormone, growth hormone, and calcitonin.

















Joints: 







The Muscular System:


Types of muscle tissues: 


















Muscle tissue is highly specialised and has four major properties:

Contractility – the ability to shorten and produce movement.

Excitability – the ability to respond to stimuli and produce action potentials.

Extensibility – the ability to stretch beyond its resting length without damage.

Elasticity – the ability to return to its resting length after stretching.

Muscle Functions & Metabolism:

Generating Motion: Skeletal muscles enable movement, precise actions, quick reactions, and communication through facial expressions, and are different from smooth and cardiac muscles involved in blood circulation and organ function.

Maintaing 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.


Muscles have additional roles, with smooth muscles regulating internal openings, pupil size, and causing hairs to stand, while skeletal muscles are voluntary and help protect internal organs.


Muscle Metabolism

  1. Creatine phosphate:During muscle relaxation, excess ATP is used to form creatine phosphate, which can be broken down during contraction to produce ATP, with excess creatine phosphate excreted as creatinine in urine.

  2. Anaerobic respiration: The most abundant energy source in muscle fibres is glycogen, and during increased activity lactic acid production may cause a ‘stitch’.

  3. Aerobic respiration: muscle tissue receives oxygen from haemoglobin (Hb) and glucose is metabolised to form ATP.

Muscle Fatigue

After a period of prolonged activity the muscle is unable to maintain its force of contraction – muscle fatigue. It primarily occurs due to changes in the muscle fibre and is thought to occur when there is:

  • Inadequate calcium released from the sarcoplasmic reticulum,

  • Insufficient oxygen (O2) supply,

  • Sepletion of glycogen,

  • Build-up of lactic acid.


Important Muscles: 

The Integumentary System:

The skin is a durable, flexible, self-repairing barrier that protects the body, prevents water and heat loss, blocks harmful agents, and with glands, hair, and nails forms the integumentary system.



















Overview and Structure of the Skin

The skin is the body’s largest organ and part of the integumentary system, playing roles in protection, sensation, temperature control, excretion, vitamin D production, and immune defence.


The skin is part of the innate immune system, acting as the first line of defence with physical and biochemical barriers that prevent harmful microorganisms from entering the body.


Structure of the skin: 

1. Epidermis (Outer Layer – First Line of Defence)

2. Dermis (Middle Layer – 90% of Skin Thickness)

3. Hypodermis (Subcutaneous Layer)









Functions of the Skin:









Stages of Wound Healing:

Understanding wound healing is important in nursing, as it occurs in the skin and follows four stages: haemostasis, inflammation, proliferation, and maturation/remodeling, linking to the skin’s structure and function.

- 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.