Bones and joints Flashcards
What is a joint
Where two or more bones meet
What are the 3 types of joints in the body? how much movement do they permit?
Synovial (allows free movement)
Cartilagenous (semi-moveable)
Fibrous (no movement)
What are the six types of synovial joints, give examples for each and briefly mention how much movement they allow
Ball and socket e.g. hip + knee joint, allows flexion/extension/abduction/adduction/inter and external rotation
Hinge e.g. elbow and knee joint, allow movement in one axis = flexion and extension
Plane/gliding e.g. acromioclavicular and intercarpal joints, allows gliding movements between flat surfaces.
Condyloid e.g. metacarpophalangeal and radoiocarpal joint, allow flexion/extension/abduction/adduction
Saddle e.g. carpometacarpal and sternoclavicular joint, allows flexion/extension/abduction/adduction. 2 articular surfaces are concave-convex and site like a saddle.
Pivot e.g. radioulnar joint and atlantoaxial joint, allow rotation around a single axis.
describe cartilaginous joints
These joints are held together by cartilage between the articulating bones
What are the two types of cartilaginous joints and describe them with examples
Synchondroses: joint where the bones are joined together by hyaline cartilage (mainly found in developing skeleton but can also be founding mature Skeleton) e.g. first sternocostal joint and growth plate
Symphyses: joint where the bones are joined by fibrocartilage, found at the skeletal midline e.g. IV discs, symphysis pubis
describe fibrous joints
these joints are held together by a dense, fibrous connective tissues, consisting mainly of collagen.
What are the 3 types of fibrous joint, give examples
Sutures: e.g. between bony plates of the skull
Gomphoses: between alveolar bone and tooth (bony socket and root of tooth)
Syndesmoses: bones are joined by ligament or fibrous connective tissue (interosseous membrane) e.g. distal tibiofibular joint
Describe/draw the structure of a general synovial joint
Periosteum (tough white fibrous membrane) covers the outer surface of the bone.
Articular/fibrous capsule supports and stabilises the joint and connects the two bones together. It is made up of irregular fibrous connective tissue. It has 2 layers:
outer fibrous membrane and inner synovial membrane.
Synovial cavity is made up of synovial membrane and synovial fluid.
The articulating surfaces fo the bones are covered in hyaline cartilage - which helps to reduce friction and absorb shock.
Additional structures may be present in the joint too, including: menisci/articular discs, bursa, extra and intra capsular ligaments, tendons, fat pads.
What is function of hyaline cartilage on a reticulating surfaces of bone?
helps to reduce friction and absorb shock.
What are the functions of synovial fluid?
Lubricates and reduces friction between articulating bones
Provides nutrients to the cartilage
Removes metabolic waste products
Phagocytic cells remove debris
what are menisci and what is their role?
they are C shaped fibrocartilage pads which provide extra shock absorption and cushioning.
what are articular discs and what is there function?
Small, oval shaped structure which strongly unites bones in a joint
what Is the function of a fat pad?
fat pad acts as a cushion and protects articular cartilage
what Is the function of an extra-capsular ligament?
provide stability, hold joint together, prevent dislocation
Why are bones considered organs?
Because they contain many types of tissues such as blood, nerves, connective tissue and bone tissue.
What are the components of bone? how much do they make up and what do they contain?
Organic component (osteoid): makes up 1/3 - mainly type 1 collagen and ground substance (proteoglycans and extracellular fluid). This gives bones flexibility.
Inorganic component: 2/3 - primarily hydroxyapatite which stores calcium and phosphate salts. These make bones brittle, giving them hardness and strength.
What are the two types of bone?
Cortical/compact
Cancellous/trabeculae
Describe the structure of compact bone and where is it found?
Compact bone is found in the shaft of long bones and on the other surface of all bones.
It is made up of osteons - cylindrical structures which contain a central canal (Haversian canal) through which nerves and blood vessels pass through. The osteons are made up of concentric layers, called lamellae. They contains osteocytes which are connected to each other by canaliculi.
What is the endosteum?
Boundary between compact and cancellous bone
what is a Volkman’s canal?
It connect the Haversian canals in osteons together, at right Angles
Describe lamellae in cortical bone and what are canaliculi.
Lamellae are concentric rings which have lacunae between them. These are spaces containing osteocytes. Canaliculi are tiny canals which run between the lacunae.
Describe the structure of cancellous bone? where is it found?
Light and porous, it is made up of many interconnected bony plates called trabeculae. Trabeculae contains osteocytes housed in lacunae and offer resistance to compressive loads. Red bone marrow fills the spaces between trabeculae.
it is found in short, flat, irregular bones and the epiphysis of long bones.
List the four types of bone cells
Osteocytes
Osteoblasts
Osteoclasts
Osteoprogenitor (osteogenic)
Describe osteoprogenitor cells
They are undifferentiated cells that can divide to replace themselves or produce osteoblasts.
Describe osteoblasts and their function and mention the enzyme they are rich in
they are non-dividing and are responsible for bone formation – they synthesise and secrete the collagen matrix and calcium salts. As the secreted matrix surrounding the osteoblast calcifies, the osteoblast become trapped within it; as a result, it changes in structure and becomes an osteocyte. They are rich in alkaline phosphatase (enzyme involved in bone mineralisation).
Where are osteoblasts located and describe their histology
On bone surface
Abundant rough ER and prominent Golgi apparatus
Describe osteoclasts, what do they originate from and what is their function?
They originate from macrophage and monocytes rather than osteogenic cells. They break down old bone. Hydrogen ions are secreted, and the acid environment removes the minerals. Proteases resorb the collagen matrix.
Describe the histology of osteoclasts
Multinucleated, have vacuoles/clear zones and a ruffled border
Describe osteocytes and their role
They are non-dividing, the most common cell type and are formed when osteoblasts become embedded in the collagen matrix in lacunae (spaces where they sit). They maintain the mineral concentration of the matrix by secreting enzymes. They also maintain extracellular calcium levels (help to remove calcium when calcium levels in the body are low)
Describe the structure of osteocytes
Star-shaped with slender canaliculi projections extend from osteocytes to adjacent lamellae.
List the functions of bones
- Structural support
- Facilitate movement
- Protects internal organs
- Produces blood cells
- Stores and releases minerals and fat
Describe the structure of long bones
Made up of diaphysis, metaphysis and epiphysis.
Diaphysis: long tubular shaft tat has central medullary cavity, The cavity contains yellow bone marrow which stores fat.
Metaphysis is at the neck of the bone. it is the meeting point of the epiphysis and diaphysis. In childhood, this is where he epiphyseal growth plate was.
Epiphysis is the wider, end of the long bone. It contains cancellous bone.
what does the epiphyseal plate turn into in a adulthood?
epiphyseal line (between epiphysis and metaphysis)
What are the components of cartilage? what are their proportions ?
Cartilage is made up of:
Cells 5% (chondrocytes)
ECM 95% (mainly type 2 collagen and water)
Does cartilage contains blood vessels or nerves?
NO
What is the function of chondrocytes?
Synthesise and maintain the ECM
What are the components of ECM?
Water (70%)
Organic (30%): proteoglycans, type 2 collagen (makes up 60% of organic), protein, GAGs, also contains hyaluronic acid chains with links containing chondroitin and keratAn sulfate.
What is the function of ECM in cartilage?
It protects chondrocytes from loading forces
What is the function of articular/hyaline cartilage?
Provides a smooth lubricated surface for articulation
It facilitates load transmission and low friction movement
What are the 3 types of cartilage?
Hyaline/articular
Elastic
Fibrocartilage
What are the two divisions of hyaline cartilage? list the different areas they are found
Skeletal: articular, costal, growth plate
Non-skeletal: trachea, larynx, nose
Where is elastic cartilage found?
Ear
Epiglottis
Where is fibrocartilage found?
meniscus
Intervertebral disc
At the outer edge of compact bone, rather than being arranged as osteons, how is the osseous tissue arranged?
As circumferential lamellae which are parallel to the outer edge of the bone
how is the lamellae arranged in cancellous bone?
Arranged as boney plates called trabeculae
what is the function of the periosteum?
thick fibrous membrane that covers the surface of the bone and serves as an attachment site for muscles and tendons
where is parallel lamellae found?
in trabecular/cancellous bone
how are compressive trabeculae arranged? how is this functionally significant?
Vertically
Weight bearing
how are tensile trabeculae arranged? how is this functionally significant?
horizontal
Supportive
how does blood supply the bones?
Nutrient foramen: external opening for entrance of blood vessels in a bone.
Volkmann’s canal: passage that carries nutrient through bone
