Musculoskeletal system (WIP)

What is cartilage, where is it found and what is it for?

strong, flexible and semi-rigid connective tissue. It can withstand compressive forces but can bend.

Found in the ear, trachea, ribs and nose

support, articulations surfaces for bones, act as a template for growth and development of bone, and is a lubricating surface to reduce friction

How is cartiledge made/ what is their structure

chondroblasts are cells in the outer layer of cartilage and secrete extracellular matrix, then become trapped in it and mature into cells called chondrocytes.

Most cartilege is then covered by a layer of dense, irregular, connective tissue called perichondrium

characteristics of cartilage

nourished by diffusion from capillaries in the perichondrium so it must be thin

slow healing

no blood vessels or nerves

Hyaline cartilage

most common cartilage and a precursor to bones.

Bluish white colour found in ribs, nose, larynx, trachea and ends of bones

translucent with a high proportion of collagen

second most flexible

White Fibrous catilage

glistening white colour in invertabral discs and join capsuole ligaments

the collagen is organised in dense fibres which makes it strongest but also the lest flexible

the fibres are oriented in multiple directions of functional stresses

no perichondrium

Yellow elastic cartilage

yellow colour found in external ear, epiglottus, laryut

numerous chondrocytes in a threadlike network of elastic fibres made of the elastin proteins

most flexible and most chonrocytes

What is bone

a stong, flexible and semi rigid support tissue resistant to bending, compression and stretch

what are the functions of bone

-support- the structural framework for the body, providing attachment sites for muscles

-Protection- protecting internal organs

-assisting movement

-mineral homeostasis for calcium and phosphorus

-blood cell production in bone marrow

What is the extracellular matrix of bone made of

-30% organic- mainly collagen providing bone’s flexibility

-70% inorganic- main component being hydroxyapatite which contains calcium and phosphate

how are bones made/ what stages do they go through

before the extracellular matrix is calcified the tissue is called osteoid tissue. When the concentrations of calcium and phosphate rise high enough they are deposited into the extracellular matrix and the bone calcifies

Features of compound bone

-surrounds most bones

-hard and gives bones the smooth white appearance

-strong and rigid

Features of spongy bone

-found at ends of bones and in vertebrae

-contains marrow where blood cells are made

osteoprogenitor cells

‘stem’ cells of bone and the source of new osteoblasts

osteoblasts

line the surface f bones, secrete collagen and the organic matrix of bone (osteoid). As they become trapped in organic matrix they become osteocytes

osteocytes

maintain bone tissue. Fine processes from these cells pass through bone and form gap junctions with other osteocytes

How do osteoclasts break down bone

They are large, multinucleated, ruffles border, secretory cells with a prominent golgi body and vesicles. They secrete enzymes lik carbonic anhydrase which acidifies the matrix and causes it to decalcify. Then they break down the matrix

How are osteoclasts made

monocytes/macrophages are derived from hematopoietic cells in the bone marrow. Monocytes travel in the bloodstream and collect at sites of bone destruction where they fuse to form osteoclasts.

How does bone remodelling occur

relies on the correct balance between bone resorption and bone deposition by osteoblasts

1-mechanical stresses on the skeleton cause release of calcium, that stimulate bone-remodelling

2- Bone breakdown is stimulated by parathyroid hormone and inhibited by calcitonin

structure of haversian systems/ osteons

-1 alignation

-2 osteocytes

-3 lacunae

they are aligned in the same direction along lines of stress which change with the stresses. Osteocytes sit in the calcified matrix in small space called lacunae

Long processes from the osteocytes lie in small channels called canaliculi which transport nutrients and waste

lacunae are arranged in concentric sings of bone amtrix called lamellae around a central haversian canal and their processes run in interconnecting canaliculi

the Haversian canal and horizontal canals contain blood vessels and nerves from the periosteum

Where is cartilage found

found in limb, vertebrae and ribs. Form as hyaline cartilage in embryos

Ossification

cartilage cells flatten and calcium salts are deposited around them. Osteoblasts secrete layers of matrix and osteoclasts break catilage down. In limbs ossification begins at caps at the ends and in the middle

Periosteum

is a dense fibrous membrane that surrounds bone. it consists of an outer fibrous layer and an inner cellular layer (cambium)

The outer layer is mostly collagen with nerve fibres that cause pain when the tissue is damaged. it contains blood vessels with branches that penetrate the bone to supply theo osteocytes

develops from perichondrium

Axial bones

-skull, sternum, ribcage, vertebral column, pelvic girdle

Appendicular bones

scapula and clavicle, pectoral girdle, hind and forelimbs

How to identify the atlas and axis

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How to identify the cervical bones in spine

-smallest

-triangular foramen with foramen in processes

-no articular facets

-smallest body and small transverse processes

Movement in cervical bones

-flexion and extension and rotation. Region with greatest movement

How to identify thoracic bones in spine

-circular foramen

-articular facets

-larger body

-thinner intervertebral discs

-large transverse processes

Movement in thoracic bones in spine

rotation and lateral flexion. prevents extension

how to identify lumbar bones in spine

Largest with the largest body (must carry the most weight)

-no articular facets and thickest intervertebral discs

-triangular foramen

-largest and bluntest transverse processes (wing shaped kinda)

Movement allowed by the lumbar bones

lest flexion and tension. rotation prevented

How to identify sacrum

bones all fused together

How to identify coccyx

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Tendon

-inelastic so it remains the same length when muscles contract

-attach muscle to bone

-fibres continuous with muscle

-energy of contraction efficiently transmitted to movement of the joint

-mostly collagen

high tensile strength

Ligaments

-holds bone is position

-collagen

-allow for some elasticity and provide strength

Types of synovial joints

-hinge joins> movement in one plane

-ball and socket joints> motion in multiple planes

-gliding joint> movement in two planes

hinge joints

one articulating surface convex and the other is concave. Strong collateral ligaments restrict movements to one plane

ball and socket joints

bone surfaces reciprocally convex and concave. rotation in all three planes

gliding joints

articulating bone surfaces nearly flat and bones glide across eachother in single plane

label

first class levers

-the fulcrum (axis) is between the load and the effort

-eg. joint between the head and first vertebrae

second class levers

-the load is between the axis and the effort

-eg standing on toes

why do second class levers have high mechanical advantages

-when a levers effort arms is longer than its load arm. High mechanical advantage means it can move large loads with a relatively small amount of force

third class levers

-most common

-effort is between the load and axis

How to calculate the force

F₁ x d₁ = F₂ x d₂