The Skeletal System Flashcards
What is the function of the skeleton
Mechanical support and protection for internal organs
What 4 things is the skeleton composed of
Bones, cartilage, joints and ligaments
What are the two major skeleton components
Axial and Appendicular
What is the axial skeleton
The central component of the overall skeleton that supports and protects the organs of the head, neck and torso
How many bones are in the axial skeleton
80
What 3 main types of bones are in the axial skeleton
Skull, vertebral and thoracic
What two types of bones does the skull consist of
Cranial and facial bones
When do the cranial plates fuse
At 2 years old
How many cranial bones are there
8
How many facial bones are there
14
Why are we born with separate plates in the skull
Flexibility for birth/ as the skull passes the birth canal/ pelvis
How many bones make up the ribcage
12 pairs of ribs and the sternum
What end of the ribs join to the thoracic vertebrae
The rounded ends
What do the flattened ends of the ribs attach to
The sternum
Which ribs are the floating ribs and why
8th- 10th ribs as do not attach to sternum
Why happens to the vertebrae bones during development
Some fuse together to form 24 bones
What are the 5 types of vertebrae bones
Cervical, thoracic, lumbar, sacrum, coccyx
How many bones are in the appendicular skeleton
126
What is the pectoral girdle
Scapula and clavicle
What bones make up the upper extremities of the appendicular skeleton
Humerous, ulna, radius (arms) and carpals, metacarpals, phalanges and sesamoid (hands)
What is the pelvic girdle
The 2 pelvic (hip) bones
What makes up the lower extremities of the appendicular skeleton
Femur, patella, tibia, fibula (legs) and talus, calcaneus, tarsals, metatarsals, phalanges and sesamoids (feet)
What is osseous tissue
Bone tissue
What does bone/osseous tissue consist of
Mineral salts, organic matrix (90% colllagen) and water
What are the functions of calcium in bone
Mechanical support, mineral homeostasis, acid-base homeostasis, defence against toxins, haematopiesis
What are the 4 components of bone general anatomy
Diaphysis, medullary cavity, epiphysis, metaphysis
What is the Diaphysis
The central tubular shaft of bone marrow that contains yellow bone marrow and blood vessels to deliver nutrients and remove waste
What are the walls of the diaphysis composed of
Dense, compact cortical bone
What is medullary cavity
Component of bone containing yellow marrow (adipocytes)
What is the epipysis
Wider section at end of bones composed of spongy bone that is covered with articular cartilage to provide shock resistance and reduce friction
Where are is the red bone marrow located
Between the spongy bone (epipysis)
What is the metaphysis
Region of bone where epiphysis and diaphysis meet, contains the epiphyseal plate
What is the epiphyseal plate
Growth plate containing transparent cartilage
What happens to the epiphyseal plate when bone stops growing
Cartilage is replaced by osseous tissue and epiphyseal plate becomes the epiphyseal line
What is the endosteum
The region where bone growth, repair and remodelling occur
What is the periosteum
Fibrous membrane containing blood vessels, nerves and lymphatic vessels that nourish the compact bone and also act as a site for attachment of tendons and ligaments
What is bone
Connective tissue made rigid by the deposition of hydroxyapatites
What are hydroxyapatites
Inorganic mineral crystals
What does the organic matrix/ osteoid in bone consist of
Collagen fibres encrusted with crystalline hydroxyapatite, glycosaminoglycans and proteoglycans
What forms the cartilage in bone
Glycosaminoglycans and proteoglycans
How is crystalline hydroxyapatite in collagen formed over time
In young bones insoluble amorphous calcium phosphate is dissolved and converted into crystalline hydroxyapatite
Describe compact bone
Dense bone with cells arranged in concentric circles that can withstand compression to provide the body with support and protection
Describe spongy bone
Cancellous bone arranged in trabeculae with open spaces to make the bone lighter to support shifts in weight distribution
Where is the site of hematopoesis (RBC synthesis)
Red marrow
What forms the calcifiable (ability to secrete minerals) matrix of bone
Collagen
What is collagen
Fibrous protein rich in amino acids that consists of tropocollagen molecules
What amino acids is collagen rich in
Glycine, proline and hydroxyproline
What are tropocollagen fibres
Rod like cylinders in collagen that consist of three separate alpha chain monomers that form a triple helix held together by weak intermolecular forces
What is native collagen
Collagen synthesised from osteoblasts (new collagen)
Which type of collagen can initiate mineral crystal formation from calcium and phosphate/ form new bone
Native collagen
What are the function of hydroxyapatite crystals
Complex of mineral salts that provide hardness and strength to bone, enable ion exchange with extracellular fluid so bone can buffer the pH of the extracellular fluid and trap toxins in bone (defence mechanism)
How do hydroxyapatite crystals enable ion exchange with the extracellular fluid
Crystals absorb excess phosphate which binds water to from a hydration shell with enables the exchange
What feature of the hydroxyapatite crystals enables defence against toxin
Ions within the crystal have a slow rate of turnover so toxins can displace calcium in the bone and remain in there for years
Which part of the bone is continually synthesised, secreted, organised, mineralised and destroyed
Bone matrix
What two cell types control bone matrix turnover
Osteoblasts and osteoclasts
What are osteoblasts
single nuclear cells that form new bone and synthesise and secrete collagen matrix and calcium salts
What are osteocytes
Mature bone cells formed when osteoblasts become encrusted within hydroxyapatite crystals/ trapped within the calcified matrix
What are osteoclasts
Multinuclear giant cells derived from macrophages/monocytes
How do osteoblasts synthesise collagen
In ribosome of osteoblasts pro collagen is secreted into extracellular space and converted into tropocollagen molecules that are polymerised to form microfibrils, these collagen microfibrils accumulate mineral ions in vesicles to form the hydroxyapatite crystals
How do osteoblasts synthesise collagen
In ribosome of osteoblasts pro collagen is secreted into extracellular space and converted into tropocollagen molecules that are polymerised to form microfibrils, these collagen microfibrils accumulate mineral ions in vesicles to form the hydroxyapatite crystals
What 3 hormone control mineral homeostasis in bone
Parathyroid hormone (PTH), calcitonin, 1,25-dihydroxycholecalxiferol (metabolically active vitamin D)
Describe the relationship between the inorganic and organic phases of bone metabolism
Intimate relationship so resorption of bone involves the destruction of both organic matrix and inorganic hydroxyapatite crystals
What is the inorganic phase of bone metabolism
Hydroxyapatite
What is the organic phase of bone metabolism
Collagen
What stimulates parathyroid hormone secretion
Low ca2+/ plasma
What is the function of PTH
Promotes bone resorption by osteocytes and osteoblasts
What is bone resorption
Breakdown of bone
What are the short term effects of PTH
In minutes increased Ca2+ from deep bone to surface and raised plasma/ca2+
What are the long term effects of PTH
Over hours/days increases number of osteoclasts which stimulate breakdown of collagen to release ca2+
Also increases formation of osteoblasts (form collagen new bone to prevent erosion in the long term)
What is PTH
84 AA polypeptide hormone with a half life of 20 minutes in blood
What is calcitonin
32 amino acid polypeptide hormone with a half life of 15 minutes in blood
Where is calcitonin secreted from
The parafollicular cells of the thyroid gland
What stimulates calcitonin secretion
A rise in plasma (ca2+ )
What are the effects of calcitonin
Reduces plasma (ca2+) by inhibiting resorption of bone by osteoclasts and prevents plasma hypercalcaemia by promoting ca2+ storage in bone
What stimulates the production of metabolically active vitamin D (1,25(OH)2vitD3)
In low plasma (ca2+)/ hypocalcaemia PTH is secreted which acts on the kidney to enhance 1alpah- hydroxylation of 25-hydroxycholecalciferol (25(OH)vitD3) to form the metabolically active 1,25-dihydroxycholecalciferol
And low plasma can also independently promote its production
What is the function of 1,25(OH)2vitD3
Promotes bone resorption via osteoclasts to increase plasma (ca2+)
What inhibits the formation of 1,25(OH)2vitD3
Hypercalcaemia and hyperphosphataemia
What is a joint
Where adjacent bones or bone and cartilage come together ( articulate) to form a connection
What are the 3 structural classifications of bone
Fibrous, cartilaginous and synovial
What are the 3 functional classifications of joints
Synarthrosis , amphiarthrosis and diarthrosis
What is a synarthrosis joint
Immobile joint e.g. sutures skull
What is amphiarthrosis joint
Slightly moveable e.g. vertebrae
What is a diarthrosis joint
Freely moveable joint e.g. synovial joints in appendicular skeleton
What are fibrous joints
Adjacent bones that directly connected by fibrous connective tissue and no joint cavity e.g. sutures of skull
What are cartilaginous joints
Adjacent bones that are directly connected by cartilage and lack a joint cavity e.g. costal cartilage of thoracic cage and anterior end of rib
What is cartilage
Tough but flexible connective tissue
What are synovial joints
Most common type of joint where Joint cavity separates the adjacent bones and ligaments or tendons attach bones/muscle
What is the joint cavity
Joint cavity walls are formed by articular capsule attached to bones and filled with synovial fluid and secreted by synovial membranes to lubricate the joint and enable flexibility
What is the articular capsule
Walls of joint cavity that are fibrous connective tissue made up of articular cartilage at the end of each bone to prevent friction between bones
What are ligaments
Fibrous connective tissue that attaches bone to bone to supports the joint and limits the range of movement
What are tendons
Attach muscle to bone and provide extra support to the joint
What are the 6 types of synovial joint
Pivot, ball and socket, condyloid, plane, saddle and hinge joints
