Bioscience week 1

Definition - joints (articulations)

Sites where two or more bones meet

facilitate body movements

Definition - Ligaments

Connect the articulating bones at a joint

Definitions - Tendons

Connect muscles to bone

Definition - Skeletal muscles

Contract to bring about body movements

Definition - Cartilage

• supports body structures

• connects bones

• maintains the shape of body structures

• resists compression

• has tensile strength

• is composed of chondrocytes (cartilage cells) and an extracellular matrix = ground substance, collagen & elastin fibres

Three different types of cartilage

1. hyaline cartilage

2. fibrocartilage

3. elastic cartilage

Learning Objective 1

List the five functions of bones, identify the main bones of the axial and appendicular skeleton, and state their classification according to their shape.

Functions of bones

• support

• protect

• storage of minerals (calcium & phosphate) and triglycerides (fat)

• blood cell production

• movement

bones func - storage of minerals (calcium & phosphate) and triglycerides (fat)

• helps maintain homeostatic blood calcium levels

  • regulated by parathyroid hormone and calcitonin

• yellow bone marrow consists of adipose tissue

  • a potential energy source

bones func - Movement

• bones act as levers

• site of muscle attachment to a bone is known as origin or insertion

• origin - fixed point of muscle attachment (bones do not move when they contract)

• insertion - moveable point of muscle attachment (bones move when muscle contracts)

two divisions of bones

• axial (green)

• appendicular (gold)

bones are classified into four groups according to shape

• The axial skeleton consists of

• Skull

  • Cranial and facial bones

• Vertebral Column

  • cervical, thoracic, lumbar, sacral, and coccyx vertebrae

• Rib Cage

  • sternum and ribs

bones are classified into four groups according to shape

• The appendicular skeleton consists of

• upper limbs (arms, forearms, and hands)

• lower limbs (thighs, legs, feet)

• shoulder (pectoral) girdles

• pelvic girdle

Bone Shapes - Long bones

• long slender bones

• have shaft (diaphysis) and bones ends (epiphysis)

Bone Shapes - Short bones

• small cube shaped bones

• patella = sesamoid bone

Bone Shapes - Flat bones

• thin flat often curved bones

Bone Shapes - irregular bones

• complex shaped bones

Learning Objective 2

Describe the composition of osseous tissue and the various functions of each component.

3 different types of tissue

• connective tissues

  • osseous tissue, adipose tissue & hyaline cartilage (growth plates)

• nervous tissue

  • sensory neurons

• muscle and epithelial tissue

  • blood vessels

Osseous tissue definition

is a connective tissue

• contains specialised cells and an extracellular matrix (aka Matrix)

The Matrix consists of

• ground substance

• collagen fibres

  • calcium phosphate crystals

The Matrix makes bones

• hard, slightly flexible and strong

Collagen fibres in The Matrix provides

• flexibility and tensile strength

Removing Collagen fibres from the bone means

• bone becomes very brittle

Calcium phosphate crystals in The Matrix makes bones

• hard

• provides compression strength

Removing Calcium phosphate crystals in The Matrix makes bones

• bone has tensile strength

• but is very soft and flexible

• lacks compressive strength

Specialised cells

• Osteoprogenitor cells

• Osteoblasts

• Osteoclasts

• Osteocytes

Osteoprogenitor cells

• stem cells that differentiate into osteoblasts

osteoblasts

bone “building”. cells - produce and secrete collagen fibres & ground substance (matrix)

Osteoclasts

• bone “resorbing” cells that break down the matrix and release stored minerals

Osteocytes

• mature bone cells that maintain the matrix

Learning Objective 3

Compare the structure, functions and locations of compact and spongy bone.

Types of Bones

Every bone has an

• outer layer of compact bone

• internal layer of spongy bone

Outer connective tissue membrane is called ____it covers and contains

Periosteum

• covers compact bone

• contains blood vessels and nerves

Internal connective tissue membrane is called ____ it covers

• Endosteum

• covers spongy bone

Compact Bone has

• Osseous tissue which is arranged into osteons.

Each osteon : is, consists of , acts as

• Is

  • runs parallel to the long axis of a bone

• consists of

  • a central canal (contains blood vessels and nerves)

  • concentric circles (hollow cylinders) of matrix

  • osteocytes - lie in between each layer of matrix

• acts as tiny weight bearing pillar

  • resist forces applied to the ends of a bone

Spongy Bone is

• osseous tissue arranged into an irregular lattice of thin needle -like structures called trabeculae

  • trabeculae are precisely orientated to resist forces from all directions and transfer weight without breaking

• is lighter than compact bone - reduces the weight of skeleton

• in long bones, mainly found in proximal and distal epiphysis

Long bone summary

Learning Objective 4

Briefly describe interstitial growth, appositional growth & bone remodelling.

bones lengthen by _____ and become wider by

1. interstitial growth

2. appostitonal growth

Interstitial growth

• occurs at the epiphyseal plates of long bones

Epiphyseal plate (hyaline cartilage)

1. new cartilage forms at the top of the plate

2. bones replace old cartilage at the bottom of the plate

Appositional growth occurs at

• outer surface of all bones

  1. osteoblasts secrete layers of new matrix onto the bone surface → becomes compact bone and the bone widens

  2. in long bones, osteoclasts slowly remove old matrix from inner surface → enlarges medullary cavity and prevents bones from becoming too heavy

Regulation of Bone Growth

• during childbirth bone growth is mianly controlled by growth hormone (GH) and thyroid hormone (TH)

• during adolescence bone growth requires (GH, TH, testosterone (males) and estrogen (females)

These hormones

1. promote the adolescent growth spurt

2. End growth → induce epiphyseal plate closure

   • rate of bone formation exceeds the rate pf cartilage formation

   • cartilage eventually replaced entirely by bone

   • epiphyseal plate becomes epiphyseal line

Bone remodelling

• occurs throughout life

• maintains bone mass and strength

• replaces old and new matrix

• involves bone resorption and bone deposition

bone deposition

osteoblasts produce “new” matrix

Bone resorption

osteoclasts break down “old” matrix

In healthy young adults the rate of bone deposition equals rate of resorption

→ bone mass remains constant

with age, a decline in sex hormones results

in a loss of bone mass as the rate of bone resorption exceeds the rate of bone deposition

• loss of calcium phosphate crystals & collagen fibres = thin, week, brittle bones

Learning Objective 5

Describe the different types of bone fractures and the four stages of fracture repair.

bone fractures is

any crack or break in a bone

Bone fractures can be classified into different types :Closed (simple) fracture

• Closed (simple) fracture

  • broken bone does not break through skin

Bone fractures can be classified into different types : Open (compound) fracture

• broken bone protrudes through the skin

Bone fractures can be classified into different types : Comminuted Fracture

• bone fragments into three or more pieces

Bone fractures can be classified into different types : Compression Fracture

• Bone is crushed

Bone fractures can be classified into different types : Greenstick fracture

• bone bends and cracks → incomplete break

Bone fractures can be classified into different types : Spiral fracture

• ragged break that occurs when excessive twisting forces are applied to a bone

Bone fractures can be classified into different types : Epiphyseal fracture

• bone breaks along the epiphyseal plate

Bone fractures can be classified into different types : transverse fracture

• bone completely breaks across the diaphysis (shaft)

Bone fractures can be classified into different types : depression fracture

broken bone is pressed inwards

Bone fractures can be classified into different types : avulsion fracture

• tendon or ligament pulls off a fragment of bone

Bone fractures can be classified into different types : Pathological fracture

• caused by a disease that weakens bone structure, e.g., osteoporosis

Bone fractures can be classified into different types : Scaphoid fracture

• common carpal bone fracture

Bone fractures can be classified into different types : Potts fracture

• a break in the medial malleolus of the tibia and/or lateral malleolus of the fibula

Fracture repair ( 4 major stages) 1. Haematoma forms

1. Haematoma forms

   • torn blood vessels hemorrhage

   • clot forms

     • site swollen and sore

Fracture repair ( 4 major stages) 2. Fibrocartilaginous callus forms

• fibroblasts produce collagen fibres

• chondroblasts produce cartilage

  • fibrocartilaginous callus splints broken bone ends

Fracture repair ( 4 major stages) 3. Bony callus of spongy bone forms

• fibrocartilaginous callus is replaced by spongy bone

• bone ends firmly united

Fracture repair ( 4 major stages) 4. Bone remodelling

• compact bone replaces spongy bone at the surface or diaphysis

• osetoclasts remove excess bone

• bone returns to normal shape

Classification of joints

Learning objective 6

Classify joints by structure and function.

Joints can be functionally classified as (3 types) based on amount of movement

• Synarthrosis - immovable joint

• amphiarthrosis - slightly movable joint

  • diarthrosis - freely movable joint

based on connective tissue that connects articulating bones, and presence or absence of joint cavity, joints can be structurally classified as (3 types)

• Fibrous

• cartilaginous

• synovial

Fibrous joints

• fibrous connective tissue unties articulating bones

• joint cavity absent

• are immovable (synarthrosis) or slightly moveable (amphiarthrosis)

Sutures - immovable

skull joints

Fibrous connective tissue (ligement)

• Tibiofibular joint (slightly movable)

Cartilaginous Joints

• Cartilage (hyaline or fibrocartilage) unites articulating bones

• joint cavity absent

• are immovable or slightly moveable joints

Synovial Joints

• Articulating bone ends are covered in articular cartilage

• Joint cavity present

• Are freely moveable (diarthrosis) joints

• allow a wide range of body movements

Structural Features of Synovial joint

Learning Objective 7

Describe the various structures of a synovial joint and state the function(s) of each structure.

General Structure of a synovial joint

The six features that define a synovial joint are:

1. Articular Capsule

2. Joint cavity

3. Synovial fluid

4. Articular cartilage

5. Reinforcing ligaments

6. Sensory neurons & blood vessels

1. Articular Capsule

• Surrounds entire joint and encloses joint cavity

• two - layers :

  • tough outer fibrous layer - stabilises articulating bones

  • inner synovial membrane - produces synovial fluid

2. Joint cavity

• separates articulating bones & contains synovial fluid

Synovial Fluid

• shock absorption

• reduces friction

• supplies oxygen and nutrients to articular cartilage cells (chondrocytes) and removes waste

Articular Cartilage

• covers the ends of each articulating bone

• shock absorption

• reduces friction

Reinforcing ligaments

• stabilise joint

Sensory neurons & blood vessels

• sensory neurons detect pain and monitor proprioception

• blood vessels - mainly supply synovial membrane

Additional Structures of a Synovial Joint - Menisci

Menisci - discs of fibrocartilage

• stabilise joint

• reduce friction

• shock absorption

Additional Structures of a Synovial Joint - Muscle Tendons

• Stabilise joint

Additional Structures of a Synovial Joint - Bursae and tendon sheaths

• bags of synovial fluid

• reduces friction between adjacent joint structures

  • Bursa

    small bags of synovial fluid pocket that lies between two structures eg.

    - tendon & bone

    - ligament & bone

• Tendon Sheath

  • Tubular synovial fluid pocket that wraps around a tendon

Additional Structures of a Synovial Joint - Fat pads

• mass of adipose tissue

• cushion & protect joint structures

Types of synovial joints and their movements

Learning Objective 8 :

List the six different types of synovial joints, their movements and examples of each.

Movements allowed by synovial joints

Type of movement allowed by synovial joints is determined by the shape of the articulating surfaces

Synovial Joints allow: Angular Movements

• Increase or decrease the angle between articulating bones

Synovial Joints allow: Rotational movements

• turn a bone around its own longitudinal axis

Synovial Joints allow: Special movements

Types Of Synovial Joints - 1. Pivot joint

• allows rotation

  • (e.g., proximal radioulnar & atlas-axis joints

Types Of Synovial Joints - 2. Plane Joint

• Allows gliding movements

  • e.g intercarpal & intertarsal joint

Types Of Synovial Joints - 3. Condylar joint

• allows flexion, extension, adduction, abduction & circumduction

  • metacarpophalangeal (knucle) & wrist joints

Types Of Synovial Joints - 4. Saddle Joint

• Allows flexion, extension, adduction, abduction & circumduction

  e.g., carpometacarpal joint of the thumb

Types Of Synovial Joints - Ball and Socket Joint

• allows flexion, extension, adduction, abduction, adduction, circumduction rotation

  • shoulder and hip joints