Skeletal system Flashcards
What does the skeletal system provide us with?
shape and movement
blood cells
a storage area for minerals
protection for some internal organs
What are the four tissues of the skeleton?
bone, cartilage, ligaments, tendons
What is bone?
highly vascular connective tissue
contains osteogenic (bone-producing) cells separated by bone matrix
collagen fibres form 90-95% of the organic part of bone
inorganic crystals (e.g. calcium phosphate, calcium carbonate, citrate) form 50-70% of bone
Collagen is more elastic than bone and consists of which two cell types?
immature chondroblasts - secrete the components of cartilage
chondrocytes - mature cartilage cells derived from chondroblasts trapped within lacunae
What are the three types of cartilage found in the body?
hyaline (transparent), fibrous, elastic
What is hyaline cartilage?
covers the ends of synovial joints
connects the ribs to the sternum
forms the larynx and part of the nose
reinforces the trachea and bronchi
What is fibrous cartilage?
contains more collagen fibres which makes it compressible and able to resist high pressures
found in areas of high stress (e.g. intervertebral discs and knee joints)
What is elastic cartilage?
contains large amounts of elastic fibres which provide flexibility
found in the external ear and the epiglottis
What are ligaments?
tough fibrous bands of dense collagen fibres and fibrocytes (spindle-shaped cells)
support internal organs and attach bones to bones, holding them together at joints
What are tendons?
composed of dense fibrous connective tissue
attach muscle to bone
How many bones does the adult human skeleton contain?
206
The human skeleton is divided into which two parts?
axial skeleton and appendicular skeleton
What is the axial skeleton?
consists of 80 bones
includes bones of the skull, vertebral column, ribs and sternum
these bones form the central axis of the body and support the head, neck and torso
What is the appendicular skeleton?
consists of 126 bones
includes bones of the arms and legs and bones that attach them to the axial skeleton (pectoral and pelvic girdles)
What are the five main functions of bone?
support, movement, storage, protection, blood cell formation
How do bones provide structural support?
they provide a rigid framework to which soft tissues and organs are attached
How do bones enable movement?
bones and muscles with joints enable movement
tendons and ligaments determine the direction and the degree of bone movement
this depends on whether skeletal muscle generates fine or gross motor movements
How do bones provide storage?
bones store essential minerals (e.g. calcium, magnesium, phosphorus)
bones release or absorb minerals in response to the body’s demands under the influence of hormones
hypercalcaemia causes excess calcium to be deposited in bone
hypocalcaemia causes calcium to be released from the bone into the bloodstream
lipids are stored within yellow bone marrow which can be released and used as an energy source as required
How do bones provide protection?
they provide a rigid structure that gives protection to most of the internal organs and soft tissues within the body cavities
cranium (skull) - protects the brain
spinal column of vertebrae - protects the spinal cord
thoracic cavity (sternum and ribs) - protects the heart and lungs
pelvic cavity - protects the bladder, rectum and anus, and reproductive organs
How are bones involved in blood cell formation?
blood cell formation occurs in red bone marrow through a process called haemopoiesis
in newborns, all bone marrow is red
in adults, red bone marrow is only found in certain bones (e.g. skull, vertebrae, ribs, sternum, pelvis, ends of the femur and humerus)
red bone marrow outside these bones changes from red to yellow and stops producing these cells through ageing
What is a long bone?
a bone that is longer in length than width
A long bone consists of which parts?
diaphysis, epiphysis, metaphysis, articular cartilage, periosteum, medullary cavity, endosteum
What is the diaphysis?
the shaft and main portion of bone
long and cylindrical shape
What are the epiphyses?
the proximal and distal ends of bone
What are the metaphyses?
between the diaphysis and epiphyses
each metaphysis contains the epiphyseal (growth) plate made of hyaline cartilage where the diaphysis can grow in length
when the bone stops growing (aged 18-21) the hyaline cartilage is replaced by bone to form the epiphyseal line
What is the articular cartilage?
a thin layer of hyaline cartilage that covers the epiphysis of one bone where it forms a joint with another bone
it reduces friction and absorbs shocks at freely movable joints
it does not contain perichondrium or blood vessels which means damage repair is limited
What is the periosteum?
the tough connective tissue membrane that covers the outside of bone (except where there is articular cartilage)
two layers
outer layer consists of dense irregular connective tissue
inner layer consists of osteogenic cells that can develop bone width but not length
What are the key functions of the periosteum?
to protect and nourish the bone tissue
to act as an attachment site for tendons and ligaments
to assist in bone repair
What is the medullary cavity?
a cylindrical cavity within the diaphysis
contains blood vessels and bone marrow
helps to reduce the density and weight of bone
the cylindrical shape allows it to retain strength to withstand forces
What is the endosteum?
a single layer of bone-producing cells which lines the inner surfaces of the cavities within the bone
What is the bone matrix?
an abundant extracellular matrix that surrounds the bone-generating cells
What does the bone matrix consist of?
water, collagen fibres, crystallised mineral fibres
Which is the most abundant mineral in the matrix?
calcium phosphate
Crystals of hydroxyapatite are formed by the combination of which two minerals?
calcium phosphate and calcium hydroxide
Which other minerals are deposited in the matrix during the formation of crystals?
magnesium, fluoride and sulphate
as the minerals crystallise they harden in the process of ossification
What determines the hardness of the bone?
the amount and type of crystallised minerals
What determines the flexibility of the bone?
the number of collagen fibres present within the matrix
calcification only occurs when collagen fibres are present
Where do the mineral salts crystallise?
initially in the spaces between the collagen fibres
around the collagen fibres when the spaces have been filled
Bone tissue consists of which four cell types?
osteogenic cells, osteoblasts, osteocytes, osteoclasts
What are osteogenic cells?
derived from mesenchymal cells (adult stem cells)
they undergo mitosis and develop into osteoblasts
they are found in the periosteum, endosteum, and within the canals that contain blood vessels
What are osteoblasts?
bone-producing cells
produce the bone matrix by synthesising and secreting collagen fibres and other organic components
initiate calcification of the matrix
What are osteocytes?
start as osteoblasts
surrounded by the matrix which makes them trapped
this means they are no longer able to secrete the matrix and become osteocytes
found in mature bone
main cell type in bone
maintain the daily metabolic function of bone by ensuring the exchange of nutrients and waste products with blood
What are osteoclasts?
formed by the fusion of around 50 monocytes and remove old bone
very large, multinucleated and mainly found in the endosteum
the plasma membrane is folded into deep ruffles and faces the bone surface
it secretes lysosomal enzymes and acids that dissolve the protein and mineral matrix
this is called resorption and is part of normal bone development, maintenance and repair
removal of old bone is usually aligned to production of new bone cells by osteoblasts
What are the functions of the many small spaces within bone?
to provide a pathway for blood vessels for exchange of nutrients and waste products
to act as a storage area for red bone marrow
Approximately what percentage of the skeleton is made up of compact bone?
80%
Approximately what percentage of the skeleton is made up of spongy bone?
20%
Approximately what percentage of the axial skeleton is made up of spongy bone?
70%
What is compact bone?
strongest type of bone tissue
What is spongy bone?
it consists of columns of bone (trabeculae)
between the columns are spaces filled with red and yellow bone marrow and blood vessels
spongy bone is always found inside bone and is protected by a layer of compact bone
it is usually found in bones that have low stress levels or where pressures are exerted from a range of directions
the spaces make spongy bone lighter than compact bone
this reduces the weight of bones which allows them to move easily when pulled by skeletal muscle
How does the blood supply pass into the interior of the bone?
via the periosteum
How do periosteal arteries and nerves enter the diaphysis?
via Volkmann’s canals
What is the function of periosteal arteries?
to supply blood to periosteum and compact bone
What is the large nutrient artery?
located near the centre of the diaphysis
passes through nutrient foramen and enters medullary cavity
divides into proximal and distal branches
What is the function of the large nutrient artery?
to supply blood to compact and spongy bone and red bone marrow of diaphysis as far as the epiphyseal line
Which two factors affect the number of nutrient foramina in each bone?
bone size
amount of red bone marrow in bone
What is the function of metaphyseal and epiphyseal arteries?
to supply blood to ends of bones and to red bone marrow
What are the three veins that carry blood away from long bones?
nutrient veins - accompany nutrient artery and exit through diaphysis
metaphyseal and epiphyseal veins - accompany their arteries and exit through their respective names
periosteal veins - exit through periosteum
Why do people experience severe pain when they have sustained a fracture or have a bone tumour?
periosteum contains many sensory nerve endings
these produce sensations of pain and are sensitive to tension or tearing
What is ossification?
the process of bone formation
During the first few weeks, the embryonic skeleton is composed of which type of cells with the general shape of bones?
mesenchymal cells (a special type of undifferentiated tissue)
Bone is formed by one of which two processes during embryonic or foetal development?
intramembranous ossification - occurs within connective tissue
endochondral ossification - occurs in cartilage
What is intramembranous ossification?
bone formation occurs with the direct conversion of mesenchymal tissue into bone
this occurs in the flat bones of the skull, the lower jaw and the scapula
What are the four stages of intramembranous ossification?
the ossification centre
calcification
trabeculae formation
development of periosteum
What happens in the first stage of intramembranous ossification?
the ossification centre forms at the site where bone will develop
it occurs when specific chemical messengers cause mesenchymal cells to group together and then differentiate into osteogenic cells and later into osteoblasts
osteoblasts secrete the extracellular matrix until they become surrounded, when it stops
What happens in the second stage of intramembranous ossification?
osteocytes lie in the lacunae and extend into the canaliculi radiating in all directions
over a period of days, calcium and other minerals are deposited and the extracellular matrix begins to harden (calcify)
What happens in the third stage of intramembranous ossification?
trabeculae develop during formation of the extracellular matrix
they fuse with one another to produce spongy bone surrounding blood vessels in connective tissue
What happens in the fourth stage of intramembranous ossification?
mesenchyme at the periphery of the bone condenses and forms the periosteum
a thin layer of compact bone replaces the surface layers of spongy bone (the centre remains spongy)
the newly formed bone undergoes remodelling and eventually becomes the adult shape and size
What is endochondral ossification?
how most bones are formed through replacement of hyaline cartilage with bone
What are the six stages of endochondral ossification?
development of cartilage model
growth of cartilage model
development of primary ossification centre
development of medullary cavity
development of secondary ossification centre
formation of articular cartilage and epiphyseal plate
What happens in the first stage of endochondral ossification?
specific chemical messengers cause mesenchymal cells to group together and then differentiate into chondroblasts
chondroblasts secrete a cartilage extracellular matrix to produce a hyaline cartilage model
perichondrium (membrane) forms around the cartilage model
What happens in the second stage of endochondral ossification?
chondroblasts become surrounded by the matrix and develop into chondrocytes
model grows in strength (interstitial growth) with secretion of the matrix and cell division of chondroblasts
cartilage model grows in thickness (appositional growth) as new chondroblasts secrete the matrix deposited on the cartilage surface
chondrocytes in the middle increase in size (hypertrophy) and deteriorate leaving a cavity in the cartilage
the matrix starts to calcify
nutrients cannot diffuse through the matrix and chondrocytes start to die and lacunae develop in spaces
What happens in the third stage of endochondral ossification?
primary ossification continues from the external surface of the bone inwards
nutrient artery enters perichondrium and calcifying cartilage via a nutrient foramen into the centre of the model
this stimulates osteogenic cells in the perichondrium to differentiate into osteoblasts
when perichondrium produces bone instead of cartilage it is called the periosteum
periosteal capillaries in the model grow into the matrix and form the primary ossification centre where most cartilage will be replaced by bone tissue
spongy bone trabeculae form when osteoblasts are deposited and secrete bone matrix over the calcified cartilage
What happens in the fourth stage of endochondral ossification?
spongy bone is broken down by osteoclasts to form the medullary cavity filled with red bone marrow
primary ossification forms the diaphysis which is made of an outer layer of compact bone, lined with spongy bone that surrounds the medullary cavity
What happens in the fifth stage of endochondral ossification?
epiphyseal artery entering the epiphyses leads to development of secondary ossification centres (usually around the time of birth)
bone formation in secondary centres is similar to that in the primary centre
the difference is that spongy bone remains in the centre of the epiphysis and no medullary cavities are formed
secondary ossification proceeds outwards from the centre of the epiphysis to the external bone surface
What happens in the sixth stage of endochondral ossification?
hyaline cartilage covering the epiphysis becomes the articular cartilage and is retained throughout life
epiphyseal plate is hyaline cartilage - responsible for growth in length of bones in childhood, replaced by bone in adulthood
What is osteoporosis?
a disease of the skeletal system associated with fragile, porous bones with significant reduction in bone mass
What is osteopenia?
a mild to moderate reduction in bone mass below average levels
it puts a person at a higher risk of developing osteoporosis
What are some of the factors that may be involved in the development of osteoporosis?
genetic factors, hormonal factors, nutrition, level of activity, increased levels of glucocorticoids (natural or artificial), excessive alcohol consumption, caffeine, smoking
Why does osteoporosis affect more women than men?
loss of oestrogen at the menopause means that osteoblast activity and synthesis of bone matrix is greatly reduced
women’s skeletons are lighter with lower bone mass
What are some of the effects of osteoporosis?
increased likelihood of fractures, height loss, bone pain, fractures of the vertebrae which may lead to kyphosis (excessive outward curvature of the spine, causing hunching of the back)
What can older women, in particular, do to reduce the risk of osteoporosis development and fractures?
take enough vitamin D and calcium and enough exercise
What are the two distinct events involved in bone length growth from the epiphyseal plate?
interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate
endochondral ossification of the hyaline cartilage on the diaphyseal side of the epiphyseal plate
How many zones are within the epiphyseal plate?
four
What is the structure of zone 1 (resting cartilage)?
layer closest to the epiphysis
contains small chondrocytes that are not actively involved in bone growth
they attach the epiphyseal plate to the epiphyses, deliver nutrients to the developing cartilage, and store materials (e.g. lipids, glycogen) needed for growth
What is the structure of zone 2 (proliferating cartilage)?
chondrocytes are slightly larger and arranged into columns
chondrocytes divide and replace dead cells on the diaphyseal side of the epiphyseal plate
they secrete the matrix and produce new cartilage through interstitial growth
What is the structure of zone 3 (hypertrophic cartilage)?
chondrocytes mature and enlarge (hypertrophy)
they are arranged into columns with a gradient of maturation
chondrocytes nearest the epiphysis are younger and less mature than cells nearer the diaphysis
What is the structure of zone 4 (calcified cartilage)?
very thin and contains large dead chondrocytes and calcified matrix
osteoclasts help dissolve the matrix and blood vessels
osteoblasts from the diaphysis enter the zone
this zone now becomes part of the diaphysis
How many stages are involved in bone thickness growth below the periosteum?
five
What happens in the first stage of bone thickness growth?
periosteal cells at the bone surface differentiate into osteoblasts
osteoblasts secrete collagen fibres and organic materials to form the bone extracellular matrix
What happens in the second stage of bone thickness growth?
as osteoblasts become surrounded by matrix they develop into osteocytes
this leads to formation of ridges on either side of the periosteal blood vessel
What happens in the third stage of bone thickness growth?
ridges fuse together and form tunnel enclosing blood vessels
periosteum has now become endosteum
What happens in the fourth stage of bone thickness growth?
osteoblasts in endosteum form concentric lamellae (plates of compact bone) that move towards the centre of the tunnel as bone continues to be deposited
What happens in the fifth stage of bone thickness growth?
as osteon (tunnel filled with bone) forms, new circumferential lamellae are deposited by osteoblasts under periosteum which causes thickening of bone
this procedure is repeated as more periosteal blood vessels become enclosed
bone thickness increases as new bone is added to the outer surface
diameter of medullary cavity increases as bone lining medullary cavity is destroyed by osteoclasts
What are two of the main factors that impact bone growth?
adequate intake of vitamins and minerals, level of several hormones
What vitamins are necessary for bone growth?
A, B12, C, D, K
What is the function of vitamin A in bone growth?
stimulates the activity of osteoblasts
What is the function of vitamin B12 in bone growth?
needed to produce bone proteins
What is the function of vitamin C in both growth?
essential for collagen formation
What is the function of vitamin D in bone growth?
necessary for calcium absorption
What is the function of vitamin K in bone growth?
needed to produce bone proteins and facilitates use of calcium for bone growth
What minerals are necessary for bone growth?
calcium, phosphorus, magnesium, fluoride, manganese
What is the function of calcium and phosphorus in bone growth?
needed in large quantities to ensure bone growth and provide bone elasticity
What is the function of magnesium, fluoride and manganese in bone growth?
needed in small quantities and help in determining the hardness of bone
What hormones are involved in bone growth?
insulin-like growth factors (IGFs), thyroid hormones, sex hormones (oestrogen and testosterone)
What are the functions of IGFs in bone growth?
most important hormones needed for bone growth in childhood
produced by liver and bone tissue in response to human growth hormone
increase protein production required for bone growth
stimulate osteoblasts to promote cell division in the epiphyseal plate and periosteum
What are the functions of thyroid hormones in bone growth?
needed for growth of all tissues, including cartilage
stimulate production of osteoblasts
What are the functions of sex hormones (oestrogen and testosterone) in bone growth?
responsible for increased activity of osteoblasts and secretion of the extracellular matrix
both hormones (particularly oestrogen) are responsible for inhibiting growth at the epiphyseal plate and stopping bone length growth
as females have higher levels of oestrogen, cessation in bone length growth occurs
this explains why females are shorter in height than males
How do weight-bearing exercises increase bone mass and density?
bone tissue can alter its strength due to changes in the mechanical stress upon it
as more stress is placed, more mineral salts are deposited, and osteoblasts produce more collagen fibres
the main mechanical stressors placed on bone results from the pull of skeletal muscles and gravity
What is bone remodelling?
old bone being replaced with new bone
the amount of bone resorption by osteoclasts is matched by new bone created by osteoclasts
the whole process takes 160-200 days
in areas of high stress (e.g. hip joint) bone may be replaced more frequently (up to three times per year)
How many stages are involved in bone remodelling?
six
What happens in the first stage of bone remodelling?
osteoclasts attach to the bone surface to be resorbed
osteoclasts secrete enzymes (e.g. collagenases and lysosomal enzymes)
What happens in the second stage of bone remodelling?
enzymes attack the organic portion of bone under their attachment seal
What happens in the third stage of bone remodelling?
osteoclasts also secrete acid which dissolves inorganic salts of the bone matrix
What happens in the fourth stage of bone remodelling?
digested organic substances and dissolved salts enter the osteoclast, pass through it and are excreted into the extracellular space
What happens in the fifth stage of bone remodelling?
osteoblasts migrate into the space created by osteoclasts and synthesise collagen, osteocalcin and other organic substances
What happens in the sixth stage of bone remodellling?
osteoblasts become surrounded by the matrix and eventually become osteocytes
What is a fracture?
a break in any bone
classified depending on the severity, shape or position of the fracture line
What are the four stages of bone healing?
formation of fracture haematoma
formation of fibrocartilaginous callus
formation of bony callus
bone remodelling
What happens in the first stage of bone healing?
blood vessels woven throughout the bone are damaged, blood leaks out and clot forms six to eight hours after fracture
haematoma destroys nearby bone cells
these dead cells attract macrophages and osteoclasts to the site to remove the dead bone
this causes localised swelling and inflammation
capillaries start to grow into the haematoma to re-establish a blood supply to the bone
this stage may take several weeks
What happens in the second stage of bone healing?
procallus is formed when new blood vessels growing into the haematoma start to organise into granulation tissue
fibroblasts from the periosteum with osteogenic cells start to enter the procallus, develop into chondroblasts and start producing fibrocartilage
a fibrocartilagenous callus of collagen fibres and cartilage closes the gap between the two ends of broken bone (this takes up to three weeks)
in the first four to six weeks of fracture healing, the fibrocartilagenous callus is very soft and a cast or other support is needed until the callus starts to ossify
What happens in the third stage of bone healing?
osteogenic cells between dead and new bone regions develop into osteoblasts and start to secrete the extracellular matrix
they form spongy bone trabeculae which join the living tissue on either side of the fracture
this forms a bony callus (lasts three to four months)
What happens in the fourth stage of bone healing?
osteoclasts resorb the dead portions of the original fracture
the spongy bone around the periphery of the fracture is replaced by compact bone
What are the six types of bone based on shape?
long, short, flat, irregular, sesamoid, sutural
What is the structure of long bones?
most common type of bone and longer than their width
mostly compact bone with spongy bone at the centre and ends
slight curvature provides strength and the ability to withstand greater pressures
vary in length
What are some examples of long bones?
femur (thigh bone, upper leg) tibia and fibula (lower leg) humerus (upper arm) radius and ulna (forearm) phalanges (fingers and toes)
What is the structure of short bones?
cuboidal in shape
composed primarily of spongy bone with a surface layer of compact bone
usually in areas where there is little movement
What are some examples of short bones?
carpal bones (wrists) tarsal bones (ankles)
What is the structure of flat bones?
flat, thin and may be slightly curved
composed of two layers of compact bone that surround a thin layer of spongy bone
structure means that flat bones provide a high degree of protection and a large area for muscle attachment
What are some examples of flat bones?
cranial bones (skull)
sternum (breastbone)
ribs and scapulae (shoulder blades)
ilium (largest and uppermost of the bones which form the pelvis)
What is the structure of irregular bones?
complex shapes
consist of spongy bone with a thin layer of compact bone
What are some examples of irregular bones?
vertebrae (back bones)
pelvic bones
some facial bones (e.g. zygomatic bones)
What is the structure of sesamoid bones?
develop in certain tendons where there is marked friction, tension and physical stress
protect tendons from excessive wear and tear and can change the direction of pull of the tendon
number of sesamoid bones varies between individuals
What are the only sesamoid bones present in everyone?
the two patellae (kneecaps)
What is the structure of sutural bones?
small, irregular-shaped bones
usually appear as additional bones in the natural suture lines of the skull
What is the skull?
the bony framework of the head
consists of 22 bones (excluding the auditory ossicles)
The bones of the skull are divided into which two categories?
cranial bones (8) - form the cranial cavity which encloses and protects the delicate brain tissue facial bones (14) - form the face
What are the eight cranial bones?
frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, ethmoid bone
What are the 14 facial bones?
two nasal bones, two maxillae (joined to form the upper jaw), two zygomatic bones (cheekbones), mandible (jawbone), two lacrimal bones, two palatine bones, two inferior nasal conchae, vomer
What is the spine?
the spinal column and the mechanical structures that it is composed of, the 33 vertebrae and the ligaments and tendons that connect them
What are the vertebrae?
individual bones of the spine
stack up to complete bone structure
vertebrae all have a similar shape but distinct sections have structural modifications for movement and protection
What is the structure of a typical vertebra?
anterior portion is the vertebral body which bears the weight
it is spongy bone surrounded by a thicker, harder shell
vertebral body connects to posterior section by two bones (pedicles)
these connect with the lamina which leaves a cavity for the spinal cord
What is the structure and function of the lamina?
consists of three body extensions - spinous process in the middle and transverse processes at either side
these vary in structure along the spine to permit and restrict movement
they are needed for attachment of muscles, ligaments and tendons
What are the five sections of spinal vertebrae?
cervical vertebrae (C1-C7) thoracic vertebrae (T1-T12) lumbar vertebrae (L1-L5) sacrum (S1-S5) coccyx
What is the structure and function of the cervical vertebrae (C1-C7)?
skull rests on cervical vertebrae at top of spine
C1 (atlas) and C2 (axis) connect skull and spinal column
C1 has no vertebral body or spinous process
C2 has bone extension (odontoid peg) which extends up into the gap in C1
this structure enables the pivotal movement of the head at the neck
C3-C7 are typically structured, although the transverse processes are short to facilitate neck movement
What is the structure and function of the thoracic vertebrae (T1-T12)?
typically shaped
T1-T10 have two articular facets which are cup-shaped to enable connection with ribs
What is the structure and function of the lumbar vertebrae (L1-L5)?
typically shaped
largest vertebral bodies as they carry most of the bodyweight
spinous processes are short and flat which helps to maintain an upright stance
What is the structure and function of the sacrum (S1-S5)?
atypical presentation
vertebrae fuse at 16-26 years
fusion allows space for spinal nerves to exit between gaps (foramina)
female sacrum is wider and shorter and more acutely curved than male sacrum
What is the structure and function of the coccyx?
atypical presentation
consists of four vertebrae which fuse in 20s
small degree of movement against sacrum
What is the structure of the intervertebral discs?
sit between bodies of two vertebrae
contain a fibrous outer ring and a gel-like pulp
when a disc ruptures, the fibrous outer ring cracks and the gelatinous core can escape
under physical stress, they can bulge and press on adjacent spinal nerves, causing pain and other symptoms
What are the functions of the intervertebral discs?
to form fibrocartilaginous joints, with vertebrae permitting their slight movement
to function as shock absorbers within the spine
What are the functions of the spinal ligaments?
to provide stability during rest and movement
to help prevent damage to the cord and vertebrae from excessive movement
What is the function of the spinal tendons?
to complement ligaments in their function, as they are fibrous tissue that can endure tension through their densely packed collagen fibres
tendons attach muscle to bone
What is the function of the spinal muscles?
to work together or individually to flex, rotate or extend the spine
How can spinal injuries be detected?
neurological assessment and medical imaging (scans such as MRI or CT)
The thoracic bones are divided into which types?
sternum and ribs
The sternum consists of which three parts?
manubrium, body and xiphoid process
What is the structure of the ribs?
12 pairs numbered from superior to inferior
posteriorly, the ribs connect with the thoracic vertebrae
different lengths (1-7 are the longest)
1-7 (true ribs) attach directly to the sternum by costal cartilage
8-10 (false ribs) attach indirectly to the sternum
11-12 (floating ribs) do not attach to the sternum but attach posteriorly to thoracic vertebrae 11 and 12
What is the main function of the thoracic bones?
to protect the organs contained within the thoracic cavity
What is the pectoral girdle?
attaches the bones of the upper limbs to the axial skeleton
consists of a clavicle and scapula on each side
What are the clavicles?
collarbones
lie superior to the first rib on each side and in a horizontal position
What are the scapulae?
shoulder blades
situated posteriorly between the second and seventh ribs on each side
What are the six types of bones that make up the upper extremities?
humerus, ulna, radius, carpal bones, metacarpal bones, phalanges
What is the structure of the humerus?
the largest and longest bone of the upper arm
What is the structure of the ulna?
located on the medial aspect of the forearm
longest of the forearm bones
What is the structure of the radius?
located on the lateral aspect of the forearm
shorter than the ulna
wider at the bottom (distal radius) than at the top (proximal radius)
ulna and radius articulate with the humerus to form the elbow joint
What is the structure of the carpal bones?
eight small bones in the wrist arranged into two rows of four bones: row one (proximal row) - scaphoid, lunate, triquetrum, pisiform row two (distal row) - trapezium, trapezoid, capitate, hamate
What is the structure of the metacarpal bones?
five bones in the palm
each bone is divided into proximal (base), medial (shaft) and distal (head) regions and numbered one to five starting at the thumb
What is the structure of the phalanges?
14 bones in the digits of the hand
two in the thumb and three in each of the other digits
The pelvic girdle is composed of which bones?
two pelvic (hip) bones
join at the front (anterior) at the pubic symphysis and at the back (posterior) with the sacrum
together they form the bony pelvis
What are the three components of each adult hip bone?
ilium, ischium, pubis
separated by cartilage in infancy and childhood
fuse to form adult hip bone by around 23 years
What is the function of the bony pelvis?
to provide support for the spinal column and the organs of the abdominal and pelvic cavities
in women, the pelvis is shaped to facilitate birth and the joints at front and back of the pelvis tend to soften in pregnancy to permit easier passage of the baby
What are the seven types of bones that make up the lower extremities?
femur, patella, tibia, fibula, tarsal bones, metatarsal bones, phalanges
What is the structure of the femur?
the longest and strongest bone in the body
What is the structure of the patella?
a small triangular sesamoid bone found at the front of the knee joint
proximal end of the kneecap develops in tendon of quadriceps femoris muscle
patellar ligament attaches patella to tibia
What is the structure of the tibia?
shin bone
stronger of the two bones in the lower leg
weight-bearing bone
articulates with femur at proximal end and forms knee joint
What is the structure of the fibula?
runs parallel to tibia on outside of leg
does not join with femur but helps to stabilise ankle joint
What is the structure of the tarsal bones?
seven bones in the ankle (tarsus):
talus, calcaneus, navicular, three cuneiform bones, cuboid
What is the structure of the metatarsal bones?
five bones in the middle of the foot
each bone is divided into proximal (base), medial (shaft) and distal (head) regions and numbered one to five starting at the great toe
What is the structure of the phalanges?
14 bones in the digits of the feet
two in the great toe (hallux) and three in each of the other digits
What is a joint (articulation)?
the point at which two or more bones meet
What are the three types of joints?
fibrous, cartilaginous, synovial
The joints are further divided into which three classifications based on movement?
synarthroses (fixed or unmovable)
amphiarthroses (slightly moveable)
diarthroses (freely movable)
What are fibrous joints?
occurs when two bones are attached by fibrous connective tissue
no joint cavity and attached very tightly
synarthroses
What are the three main types of fibrous joints?
suture, syndesmosis, gomphosis
What is the structure of a suture?
found between bones of skull
tissue between bones is dense irregular collagenous connective tissue
periosteum on inner and outer surface of adjacent bones continues over the joint
What is the structure of a syndesmosis?
found in lower legs between distal tibia and fibula (distal tibiofibular joints) and in forearm between radius and ulna (radioulnar joint)
formed with a sheet of fibrous tissue (ligament) or bundle of fibrous tissue (interosseous membrane) between bones
amphiarthroses
What is the structure of a gomphosis?
formed with collagenous connective tissue
specialised joints of pegs fitting into sockets
found between teeth and mandible and maxillae joined by periodontal ligaments
amphiarthroses
What are cartilaginous joints?
connected by cartilaginous material
no joint cavity
What are the two types of cartilaginous joints?
synchondrosis (primary) and symphysis (secondary)
What is the structure of a synchondrosis?
associated with bone growth
hyaline cartilage involved in bridging the gap
e.g. epiphyseal plate, joint between manubrium and first rib
joints may be temporary and hyaline cartilage can be replaced with bone (bony joint)
What is the structure of a symphysis?
ends of the bone are covered by hyaline cartilage
fibrocartilage connects the ends of two bones
permanent joints designed for strength and resilience
found in the midline of the body
pubic symphysis connect the two pelvic bones and becomes more flexible at pregnancy to facilitate birth
What are synovial joints?
most common type of joint in the body
synovial cavity between the ends of articulating bones
diarthroses
friction at joint is low because the articular cartilage is elastic and the joint is filled with synovial fluid
all joints contain articular cartilage, articular capsule and joint cavity
What is the structure of the articular cartilage?
covers the ends of articulating bones
composed of hyaline cartilage which creates a smooth slippery surface
this reduces friction and acts as a shock absorber between ends of bones
What is the structure of the articular capsule?
composed of two layers - outer fibrous membrane and inner synovial membrane
acts as a sleeve-like structure to enclose the synovial cavity
What is the structure of the fibrous membrane?
composed of dense irregular connective tissue (mainly collagen fibres) that attaches to the periosteum of articulating bones
facilitates movement and provides stability
some fibrous membranes are arranged into parallel bundles as ligaments to provide additional strength to the joint and prevent it dislocating
What is the structure of the synovial membrane?
composed of areolar connective tissue with elastic fibres to enable the membrane to stretch during movement
may contain collections of adipose tissue called articular fat pads (e.g. intrapatellar fat pad in knee)
What is the structure of the joint cavity?
filled with synovial fluid secreted by the synovial membrane
viscous, clear or pale yellow liquid which contains hyaluronic acid and interstitial fluid
fluid contains phagocytes that digest and remove microbes and debris produced by wear and tear
it forms a thin film over the articular capsule surfaces
What are the functions of the joint cavity?
to lubricate the joint and prevent friction
to absorb shock
to provide nutrients and oxygen
to remove waste products and carbon dioxide
What are accessory ligaments?
intracapsular or extracapsular ligaments
Where are extracapsular ligaments found?
outside the articular capsule
e.g. tibial and fibular collateral ligaments of knee joint
Where are intracapsular ligaments found?
inside the articular capsule but outside synovial cavity
e.g. anterior and posterior cruciate ligaments of knee joint
What are articular discs (menisci)?
crescent-shaped pads of fibrocartilage
lie between the ends of articulating bones
attach to fibrous membrane
What is a labrum?
a fibrocartilaginous lip
extends from the edge of the joint socket (particularly in ball and socket joints)
e.g. hip and shoulder
What are the functions of the labra?
to increase the surface area of contact
to deepen the joint socket
What are the six types of synovial joints?
hinge, pivot, ball and socket, saddle, condyloid, gliding
A hinge joint produces which types of movement?
flexion/extension
A pivot joint produces which type of movement?
rotation of one bone around another
A ball and socket joint produces which types of movement?
flexion/extension/adduction/abduction/internal and external rotation
A saddle joint produces which types of movement?
flexion/extension/adduction/abduction
A condyloid joint produces which types of movement?
flexion/extension/adduction/abduction
A gliding joint produces which type of movement?
gliding movement
What are the 12 types of movement?
extension, flexion, abduction, adduction, circumduction, supination, pronation, plantar flexion, dorsiflexion, rotation, inversion, eversion
What is an extension?
increases the angle/distance between two bones or body parts
What is flexion?
decreases the angle of a joint
What is an abduction?
moves away from the midline
What is adduction?
moves closer to the midline
What is circumduction?
a combination of flexion, extension, abduction and adduction
What is supination?
rotation of hand and forearm - turns the palms up
What is pronation?
rotation of hand and forearm - turns the palms down
What is a plantar flexion?
lowers the foot (points the toes)
What is dorsiflexion?
elevates the foot
What is a rotation?
moves a bone around its longitudinal axis
What is an inversion?
turning the sole of the foot inwards - outer side of foot on the ground
What is an eversion?
turning the sole of the foot outwards - inner side of foot on the ground
