36 - The Skeleton And Muscles Flashcards
Functions of the skeleton
Support - rigid framework, holds body upright
Protection - skull protects brain, vertebrae protects nerves of spinal cord, ribs protect heart and lungs.
Movement - rigid levers against which muscles can pull
Shape - long bones - tall, feet bones - determine width
Manufacture - bone marrow makes red blood cells, white blood cells and platelets
Structure of the human skeleton
has 206 bones, divided into axial and appendicular skeletons.
Parts of the axial skeleton
Skull, spine, ribs and sternum (breastbone)
Skull
Consists of 20 bones fused together
Spine - The vertebrae and regions
33 bones called vertebrae arranged into 5 regions Cervical (neck) - 7 Thoracic (chest) - 12 Lumbar (back) - 5 Sacrum (hip) - 5 Coccyx (tail) - 4
Spine - intervertebral discs
Top 24 vertebrae held together by ligaments can move slightly
Separated by (intervertebral) discs of cartilage.
Have harder outer layer and soft jelly- plise centre.
Act as shock absorbers and protect vertebrae.
Last nine vertebrae are fused together, no discs, no movement, together to form the sacrum and coccyx.
Slipped disc
When the soft centre of a disc bulges out and compresses some spinal nerves. May result in pain in the back or leg, condition is often called a ‘slipped disc’
Transverse section (TS) of a typical vertebra
Facet - where next vertebra rotates against
Neural spine - for muscular attachment
Transverse process - for muscular attachment
Neural canal - contains the spinal cord
Centrum - gives strength
[Look at Diagram]
Rib cage
Consists of the sternum (breastbone) and 12 pairs of ribs.
All ribs are attached to the vertebrae of the spine.
The top 7 ribs are attached to the breastbone at the front - true ribs
Next three ribs, attached to each other at the front of the chest by cartilage - false ribs
The bottom two ribs, only attached to the spine, do not attach to anything at the front of the body - floating ribs
Parts of the appendicular skeleton
Limbs, pectoral (shoulder) girdle and pelvic (hip) girdle
Pelvic girdle
Each half of the pelvic girdle consists of three fused bones.
The two halves are joined by a band of flexible cartilage.
Fused to the spine at the sacrum.
Hollow cavity where the hip bones attach to the sacrum called the pelvis.
Pelvic girdle also connected to the legs, (femur, patella, Tibia, Fibia, Tarsals, metatarsals and digits (toes) which contain the phalanges.
Limbs
Each limb end in five digits, (fingers or toes) for this reason they are called pentadactyl limbs.
Phalanges are the individual bones of the fingers and toes.
Each finger and toe has three phalanges, except the thumb and big toe, which only have two phalanges.
Cartilage
Contains a firm but flexible fibrous protein called collagen.
Lacks blood vessels and nerves.
Depends on materials diffusing through to the cells that form for transport (compared to bone, which has a rich blood supply)
This is why cartilage is slower to heal than bone.
Found in the pinna of the ear, the nose, the trachea and in the discs between the vertebrae. Cartilage also covers the ends of bones.
Function of cartilage
Cartilage protects bones (by acting as a shock absorber) and allows friction-free movement.
Structure of long bone - external structure
Enclosed by a membrane called the periosteum.
Contains blood vessels and nerves.
Long shaft of bone, diaphysis.
Head of a bone, epiphysis
Structure of a long bone - internal - compact bone
Compact bone is made of bone forming cells in bedded in a surrounding medium or matrix the matrix is composed of 70% inorganic salts such as calcium phosphate and 30% protein called collagen bone cells supplied with nutrients by blood vessels nerve fibres also run through out the bone.
Compact bone mostly found in shaft diaphysis also located as a layer around the end epiphysis.
Function calcium salts gives strength protein gives flexibility
Structure of a long bone - internal - spongy
Like compact bone contains numerous hollows network
of thin bony bars
spaces filled with red bone marrow produce blood cells found in the end epiphysis
function makes blood cells give strength and rigidity to the skeleton
Structure of a long bone internal structure medullary cavity
Contains bone marrow
in young people bone marrow is full of active red marrow which makes blood components
adults active marrow is confined to the spongy bone.
The medullary cavity of adults contains inactive yellow fat-rich marrow which can convert to red morrow if required for increased blood cell formation
Bone growth
Embryonic cartilage replaced with bone eight week of development
bone forming cells osteoblasts produce collagen
hard compound mainly calcium phosphate forms around collagen fibres
osteoblasts become trapped in this hard compound and become dormant bone cells
Growth plate
Increase in the length of bone due to growth plate made of cartilage found between the epiphysis and diaphysis of bone in the growth plate
Cartilage is continually formed and turned into bone (ossified)
Ceases to function once person becomes adult limits growth of bones and height of individual
Bone development
Dissolve them replaced at least 10 times during the life of each bone bone material being removed from interior of the medullary cavity
Extra bone material being deposited on the outside of the bone insures bones become larger but do you not become too heavy
large bone digesting sells (osteoclasts) digest bone that lines the cavity and deposit is calcium from the bone into blood vessels these are catabolic cells.
Osteoblasts form new bone to replace the bone destroyed.
Bone digesting cells and osteoblasts work in conjunction to enlarge the medullary cavity and thicken the compact bone lining it.
Renewal of bone
Continual renewal of bone is dependent on physical activity hormones and diet
when bones are stressed by physical activity they become thicker and stronger (osteoblast simulated) especially at sites where muscle attach to bone, a lack of stress on bones cause them to become thin.
The main hormones affecting bone development are growth hormone sex hormones and parathormone.
Growth hormone and many sex hormones increase the size of bones can be seen clearly at puberty ,bone mass in the body may increase rapidly.
Parathormone remove calcium from bone happens so calcium in the blood can be raised which is essential for muscles and nerves to work properly essential to have sufficient supplies of calcium in diet to replace calcium lost from bone.
Immovable joints
Immovable fixed or fused joints include the skull and pelvic girdle the junction between fused bones is called a suture.
These joints provide strength support and protection.
A joint
Where two or more bones meet
Slightly movable joint
The vertebrae upper spinal column are slightly movable.
in these joints bones are separated by a disc of cartilage, bones are held in place by ligaments which limit the amount of movement possible in order to protect the nerves of the spinal cord.
Freely movable synovial joints
Ends of bones are covered with cartilage bones are separated by a cavity held in place by ligaments prevent excessive movement of bones bones at joints are enclosed in a synovial membrane secretes synovial fluid.
This fluid lubricates the joint and reduces friction in the joint.
ball and socket joint and hinge joints are examples.
ball and socket joints for example the shoulder and hip allow movement in all directions, unable to support heavy loads
hinge joints example the elbow and knee allow movement in one direction they can support heavy loads.
Ligaments
Strong fibrous slightly elastic tissues that connects bone to bone flexible one warm hence the need for warming up exercises to prevent ligaments from being damaged
Tendons
Strong flexible in in elastic fibres that connect muscle to bone composed of collagen contain some blood vessels
Musculoskeletal disorders arthritis
Cause
inflammation swelling of a joint.
Osteoarthritis most common type occurs from 50 years of age onward cartilage in synovial joints wear down underlying bones enlarge more Synovial fluid forms joints become sore and stiff
Affects about half 1 million people in Ireland
Rheumatoid arthritis is the most severe form of joint inflammation caused genetically, autoimmune disease synovial membranes are attacked first, joint swells, damaged and deformed
3% of Irish people have some signs of this disease 75% of females occur at any age
Prevention and treatment
Reducing damage to joints use proper footwear when running avoid running on hard surfaces exercising by walking or swimming instead of running.
No cure for either form arthritis
rest exercise to maintain mobility and strength
weight loss anti-inflammatory medication steroids drugs reduced immune response and possibly surgery to replace the joint
Skeletal muscle
600 skeletal muscles in the body make up 50% of bodyweight concerned with body movements can contract quickly but tires easily
voluntary or conscious control
Smooth muscle
Found in internal structures such as digestive system blood vessels, bladder and uterus contract slowly slow to tire under involuntary or unconscious control
Cardiac muscle
Cardiac muscle is found in the heart it has many mitochondria contract strongly and does not tire as easily as skeletal muscle it is involuntary are not under conscious control
Antagonistic pairs
Muscular contraction is an active process requires energy in the form of ATP muscles are connected to bone by tendons when the muscle contracts the tendon paws on the bone causing it to move.
Muscles can only pull by contracting or shortening they cannot push push for example in the forearm and muscle on top of the humerus called the bicep contracts to pull the lower arm up a second muscle is required to straighten the lower arm this is a smaller weaker muscle called tricep located at back of the humerus it contract to straighten the arm the bicep is a flexor and closes the joint the tricep is an extensor it opens the joint
