L.2 - skeleton Flashcards
The skeleton in the vertebrates is comprised of what?
- the skeleton in the vertebrates is composed of bone & cartilages
What are the categories bone is divided into?
- 2 types: spongy and compact.
Explain the ‘compact’ type of bone.
- dense and hard
- Forms outside of the long bones.
- It is composed of Haversian systems
- The central Haversian canal containing blood vessels which branch through the bomb.
- surrounding the canal are concentrically arranged lacunae which contain the osteocytes. 
Explain the ‘spongy’ or ‘cancellous’ type of bone.
- found in the interior medullary cavity of long and other bones where it forms a network of trabeculae between the marrow.
Memorize & label the haversian system diagram (slide 5)
How is the lacunae connected together?
- by a system of radiating canaliculi which allow the supply of nutrients to the osteocytes.
Bone is a constant state of ….?
- remodelling and adaption
What are bone cells called and how are they present?
- called osteoclasts.
- are present in small numbers which can cause bone erosion or resorption (remove damaged bone)
What are osteoblasts?
- cell type that secrete the new bone extracellular matrix
What is the bones extracellular matrix composed of?
- 80% calcium phosphate on the form of calcium hydroxyapatite crystals
- 20% organic stuff - largely protein - mainly type 1 collagen
What is the lifelong cycle of bone maintenance (repair) and resorption called?
- bone remoddeling
What is the process of bone remodelling?
- during development of the skeleton, bone growth occurs independent of osteoclast removal of bone.
What is periosteum?
- It is a dense layer of vascular connective tissue envelope thing phone except a joint.
There are two layers:
1. Outer fibrosis layer - contains fibroblasts
2. Inner osteogenic layer / contains progenitor cells that differentiate into osteoblasts
Contains nerve endings that make it sensitive
What is endosteum?
- lines the inner surface of the medullary cavity of all long bones.
- it is the thin vascular membrane of connective tissue
- osteoclasts resorption of bone occurs from endosteal side.
Where do osteoclasts resorption of bone occur?
- osteoclasts resorption of bone occurs from endosteal side.
What are the functions of cartilage?
- support soft tissue
- provide low friction surface for bone articulation at joints
- enable growth of the long bones
What are the 3 types of cartilage?
- hyaline - most common. Moderate amount of collagen fibres (articulating surface joints)
- elastic - contains elastic fibres in addition to collagen (external ear)
- fibrocartilage - very low number of cells, high collagen fibre content (intervertebral disc)
In the cartilage, what is not present?
- no blood vessels (avascular), lymphatics, or nerves
Explain the structure of the cartilage.
- more flexible than bone but confers insufficient rigidity to withstand gravity.
The semi-rigid structure of the cartilage is made up of what extracellular ground substances?
- Proteiglycans (aggrecan)
- Glycosaminoglycans (chondroitin, sulphate, hyaluronix acid)
- Collagen (type 2 collagen) and in some types of cartilage, elastic fibres.
What are the spaces in the cartilage called and what do they contain?
- called lacunae
- contains chondrocytes
Some cartilages remained unchanged while others….
- ossify
What are the 2 classes of the skeleton?
- classified into dermal and endoskeleton
How does the dermal skeleton develop? What is this process called?
- in dermal bones, osteoblasts from the periosteum convert foetal connective tissue (mesenchyme cells) to bone.
- called intramembranous ossification
Where are dermal bones found?
- skull
- jaw
- pectoral girdle
What are the 2 categories the endoskeleton divides into?
- visceral skeleton: only found in larynx, tracheal cartilages, ossicles.
- somatic skeleton - found in all the rest
What are the two parts of the somatic skeleton divided into?
- the axial skeleton
- the appendicular skeleton
What is the axial skeleton comprised of?
- skull, vertebral column (including the sacrum), rubs, and sternum.
What are the 5 regions that the axial skeleton divides into?
- cervical (7)
- thoracic (12)
- lumbar (5)
- sacral (5)
- caudal (4 fused as coccyx)
What are the 2 principle elements that all vertebraes have?
- a centrum
- a neural arch
What does the neural arch do?
- it forms a canal for spinal cord
How many processes are on each vertebrae?
- typically there are 7 processes
What is between each vertebrae?
- an intervertebral disc of fibrocartilage
The appendicular includes all the rest of the body including…?
- pectoral girdle: clavicle, scapula
- upper limb: humerus, radius, ulna, carpal bones, metacarpals, phalanges
- pelvic girdle: hip bone (ilium, ischium, pubis)
- lower limb: femur, tibia, fibula, tarsal bones, metatarsals, phalanges
- sesamoid bones: develop in tendons as they turn corners - the patella or knee cap is an example.
What happens in the foetus?
- cartilage models the shape of the future adult bone
Describe endochondral ossification
- In the foetus, cartilage models the shape of the future adult bone
- may persist for months or years before being invaded by osteoblasts for conversion to bone with layering down of minerals, calcium, and phosphate
- ends of bones - epiphyses - the last parts of a long bone to ossify
- until ossification is complete, the epiphysis remains separated from the shaft (the duaphysis) by the epiphysesl plate of hyaline cartilage
What are the ends of bone called?
- epiphyses
What is the shaft called?
- the diaphysis
What are not penetrated by blood vessels?
- epiphyseal (growth) plates. So nutrient artery of the diaphysis contributes no supply to the epiphyses of long bone until after epiphyseal plate has disappeared.
What can damage to blood supply result in?
- death (necrosis of the bony tissue and if this affects the growing end of a bone in children, normal development is delayed or prevented.
What happens to the bone shaft during the endochondral bone growth?
- it is thickened by the addition of perichondral bone.
- This is formed like membrane dermal bone in successive layers.
What can too much natural growth hormone BEFORE the epiphyses have united leads to…?
- gigantism
What can too much natural growth hormone (eg. pituitary tumour) AFTER the epiphyses have united leads to…?
- acromegaly (large extremities)
What does growth hormone delay when abused by young athletes?
- fusion of the epiphyses
What is achondroplasia?
- a genetic condition due to a rare autosomal dominate mutation.
- failure of long bone endochondral ossification, especially humerus and femur
What are joints?
- are the junction sites of two or more bones of the body.
What are the two basic types of joints?
- non-synovial and synovial
What are the non-synovial joints?
- fibrous joints
- bone - fibrous tissue - bone
- example: inferior tibiofibular, structures of skull
- little movement, except that fetal skull bones move during birth. - Cartilaginous joint
- two types are found
- as age advances, cartilaginous joints may ossify
• primary cartilaginous
- bone - hyaline cartilage - bone
- all ossify except first rib sternum
• secondary cartilaginous
- bone - hyaline - fibrocartilaginous disc - hyaline - bone
- symphyses
What are the synovial joints?
- freedom of movement
- articular surfaces covered by articular cartilage and between them is the synovial cavity.
- synovial membrane does not cover articular surface themselves
- synovium is specialized tissue that produces synovial fluid for lubrication
- found outside of joints in places where friction resistance is necessary: bursas an synovial sheaths
What is a ldisease of the synovium called?
rheumatoid arthritis
