Skeletal system Flashcards
How many bones in an adult human body
206 named bones
How many bones roughly does an infant have?
Approx 300
What are the main roles of the skeletal system?
To provide structural support
Production of RBC in red bone marrow via hemopoieses
Stores minerals e.g., Ca and P
Protects internal organs
What are the 3 types of cartilage?
Hyaline
Elastic
Fibrocartilage
What is the cartilage made up of and it’s properties?
Mostly water, it contains no blood vessels or nerves
Cartilage is very flexible and strong, it can be compressed and then reversed to its original shape. The thickness of the cartilage causes diffusion of nutrients to pass through the matrix to enter cells
What is the perichondrium?
The perichondrium surrounds the cartilage, it is a dense irregular tissue. It acts as a reinforcement and prevents external expansion. It has blood vessels. No perichondrium at synovial joints
Describe elastic cartilage
Contains more elastic fibres than hyaline cartilage
Are involved in repeated bending movements
Found only in external ear and epiglottis
Describe hyaline cartilage
is the most abundant form of cartilage,
involves in structural support and flexibility
Has spherical chondrocytes
Only fibre is collagen fibres
It covers the end of most movable joints (articular cartilage)
Connects the ribs to sternum (costal cartilage) aids in respiring
Supports the nose (nasal cartilages) and the respiratory system (respiratory cartilage)
Contain perichondrium
Describe fibrocartilage
Consist of parallel rows of chondrocytes which alternate with thick collagen fibres
Can be highly compressed and contain great tensile strength
Found in locations associated with stretch and pressure e.g., knees and discs between vertebrae
Acts as shock absorbers
Protects integrity of skeleton
Name the 2 types of growth of cartilage
Appositional growth and interstitial growth
Explain appositional growth
cartilage forming cells surrounding the perichondrium secrete a new matrix against the external face of the existing cartilage tissue
Explain interstitial growth
Interstitial growth: the lacunae bound chondrocytes divide and secrete and new matrix which expands the cartilage from within, stops growing during adolescence when the skeleton stops growing
Describe the similarities and differences between bone and cartilage
Bone and cartilage both are surrounded by the perichondrium, they both use appositional growth, however only cartilage uses interstitial growth. Cartilage has no blood vessels or nerves unlike bones which do. Cartilage has chondrocytes whereas bones contain osteocytes
Cartilage’s matrix is made by chondrocytes whereas bones is made by osteoblasts
Describe the functions of the bones
Support: bones provide framework that supports and cradles organs, e.g., bones for lower limbs support the body trunk when we start, ribcage supports thoracic wall
Protection: fused bones of skull protect the brain, the vertebrae support the spine, ribcage supports vital organs
Anchorage: skeletal muscles that attach to tendons, use bones as levers to move the body and its parts. This allows us to walk and breathe. The design of joints determines the movements
Mineral storage: Bone is used for storage of minerals (calcium and phosphate), these are released into bloodstream in ion form to be distributed. Withdrawals and deposits of minerals from bones goes on continuously
Blood cell formation made in the bone marrow via haemopoiesis, (red marrow)
Triglyceride: fat is stored in the bones, yellow marrow in cavities
Hormone production: osteocalcin is produced in bones which regulates insulin production, glucose homeostasis and energy expenditure
Name the divisions of the skeleton
Appendicular skeleton & axial skeleton
Explain appendicular skeleton
The appendicular skeleton refers to limb bones and the pelvic girdle, these bones are involved in movement and response to our environment
Explain the axial skeleton
The axial skeleton refers to the long bones of the body, e.g., ribs, vertebrae
These bones are involved in protection of our internal organs, anchoring organs in place & support
What are the 4 types of bone shapes
Long, short (sesamoid), irregular and flat
Describe and name an example of each bone shape
Long bones are longer than wide, consisting of a shaft with 2 ends. e.g., tibia & fibia
Short bones are cube-shaped, e.g., parts of the wrist and ankle
Irregular bones don’t fit into any category e.g., hyoid bone
flat bones are thin, flat and sometimes curved e.g., plates of the skull
What do we call the 2 type of bone structures
spongy and compact bone
What is a sesamoid bone and it’s function?
A sesamoid bone is a form of short bone involved in altering the direction of a tendon pull. e.g., the patella
Describe spongy bone structure
Is the internal layer of the bone, has trabeculae bone (small needle like structures) open gaps between the trabeculae are filled with red/yellow bone marrow, has no osteons, irregular arrangement of lamellae, osteocytes are connected by canaliculi
What is an osteon?
A cylindrical structure composed of bone tissue known as lamellae, they surround a central canal
Describe the structure of compact bone
It is smooth and solid external layer of the bone. The compact bone is covered inside and outside by periosteum and endosteum. They contain bone marrow, but no defined bone cavity. They form movable joints and are covered by hyaline cartilage. they have no shafts or expanded ends
What is the diaphysis?
also known as the shaft, forms the long axis of the bone, it surrounds central medullary cavity that contains no bone tissue
What is the medullary cavity
A cavity surrounded by the diaphysis, it contains no bone tissue, but yellow marrow
w which is made of fats and lipids, between the cavity and diaphysis there is a thin layer of spongy bone
What is the empiphysis?
are the ends of bones, the outer shell of the compact bone forms epiphyses exterior. A thin layer of hyaline cartilage covers each surface of epiphyses. It cushions the bones and acts as a shock absorber during movement
What is the empiphysis line
found between the diaphysis and epiphyses, this signifies the remains of the epiphyseal plate (growth plate) is a disc that grows during childhood to lengthen the bone. The flared portion is known as the metaphysis
Describe the Periosteum
tough fibrous layer, lots of collagen fibres, attached to the bone by sharpeys fibres. osteogenic layer (cambium) sharpey fibres penetrate this layer, cambium has a rich blood supply, lots of vessels, yellow bone marrow made of fats (fat storage)
Describe the endosteum
endosteum- internal layer lines the medulla cavity and the canals in the bone, provides a source of cells and osteoclasts, which remove inner parts of bone as bone grows to maintain a certain thickness throughout the bone
What are the 3 types of bone markings?
projections
surfaces
depressions
Where is red bone marrow found
flat bones of the skull, sternum, ribs, clavicle, hip bones, scapula, vertebrae, heads of the femur and humerus,
Name the 4 stages involved in bone repair
- Hematoma
- soft callous formation
- Hard callous formation
- Remodeling
Describe stage 1 of bone repair
S1: A hematoma is formed, as the bone breaks the blood vessels within and surrounding are torn, this causes blood clots to form, nearby bone cells begin to die due to lack of nutrients, bone becomes swollen, inflamed and painful
Day 0-2
Describe stage 2 of bone repair
S2: soft callous forms, blood vessels begin to penetrate blood clot. Fibrocytes and chondrocytes flood to area of break. Fibroblasts produce collagen fibres which span the break and connect 2 broken ends together. Osteogenic cells produced the Chondrocytes to secrete a new matrix which bulges out and later calcifies forming the soft callous
production of granulation tissue which supplies capillaries
Day 2-4
Describe stage 3 of bone repair
S3: formation of hard callous (bony callous) the osteogenic cells differentiate into osteoclasts and osteoblasts.
Osteoblasts begin to form spongy bone, trabeculae forms which spans the broken bone and joins 2 broken ends together. The soft callous is replaced by immature bone, forming the hard callous. remaining granulation tissue is removed
Day: up to 6 weeks
Describe stage 4 of bone repair
S4: remodeling, this occurs throughout the formation of bony callous, it involves the removal of excess and the formation of new shafts of bone via osteoclasts and osteoblasts, this leads to the original shape of the bone being reformed. osteocytes can sense strain on bone which leads to further adjustments during remodeling. Bone can be completely restored if properly supported.
This make take up to several years
Role of osteogenic cells
These are stem cells found in the bone marrow, they then specialize e.g., into osteoblasts. in growing bones they are flat squamous cells
Role of osteoblasts
They secrete bone matrix and fibres, creating the bony structure which acts as a scaffold, they secrete 90% of collagen and calcium that make up an osteoid, they are cubed shaped and once surrounded by matrix become osteocytes
Role of osteoclasts
Giant multinucleated cells involved in bone resorption, main role in removal of bone. They lie in depressions carved in bone (lacuna). they have a ruffled border which increases the SA for enzymes to break down bone and seal matrix. They trim down bone and remodel it, closely working with osteoblasts
Role of osteocytes
They sit in lacunae, they control osteoblasts and osteoclasts, by regulating and sensing strains & stressors of the bone. They respond to mechanical stimuli and can trigger remodeling of bone.
Define the role of canaliculi and their formation
Canaliculi extend from the lacuna and connect to the central canal.
It forms as osteoblasts secrete bone matrix and become trapped within it becoming osteocytes. This leaves little canals filled with tissue fluid. Canaliculi tie osteons and osteocytes together enabling communication, nutrition and waste to be shared. allowing bones to be nourished
Name the 2 types of lamellae & the differences between them
inisitial lamellae- are incomplete, fill gaps in osteons or remains of osteons during remodelling
circumferential lamellae-found deep in the periosteum, extend from diaphysis, prevent twisting of bone
Explain the chemical composition of bone
It contains organic as well as inorganic components
organic- osteocytes, osteoblasts, osteoclasts, osteoprogenitors cells, collage fibres
inorganic-hydroxyapatites (mineral salts take up 65% of mass)), calcium phosphates needed to create hardness of bone, allows compression of bone to be resisted
