Lecture 13 - Bone Flashcards
What is ossification?
The formation of bone
How many types of ossification are there?
2
What are the 2 types of ossification?
Endochondral ossification
Intra-membranous ossification
What is EndoCHONDRAL Ossification?
Formation of LONG BONES from a Hyaline CARTILAGE TEMPLATE
CHONDRAL = Cartilage
Continued growth and lengthening at epiphyseal plate (appositional growth)
So what is Appositional Growth and therefore Endochondral Ossification?
Chondrocytes at epiphyseal plate secrete new bone matrix/tissue at the surface of the bone.
Bone gets added to existing surface
This causes the bone to grow outwards expanding and widening
What is Intra-membranous ossification?
Formation of bone from clusters of Mesenchymal Stem Cells (MSC) in the centre of the bone
Interstitial growth (growth in middle)
What Bones does Endochondral Ossification form?
Long Bones (E.g):
Tibia, fibula, femur, metatarsals and phalanges of LOWER LIMB
Humerus, radius, ulna, metacarpals and phalanges of UPPER LIMB
What bones does Intra-membranous ossification form?
Flat Bones of the skull and face
Most Cranial Bones (Part of Skull)
Clavicle
How many bones in the body?
206
Bone functions
Support body
Protect Organs
Storage/reserviour of inorganic substances (CALCIUM and PHOSPHORUS)
Haemopoiesis
Fat storage (yellow marrow)
Acid-base homeostasis (Calcium is alkali)
What type of tissue is Bone?
CONNECTIVE Tissue
If Bone is a connective tissue what is it made up of?
Cells (Osteoblasts, osteocytes and osteoclasts)
Collagenous fibres
Hard calcified matrix (only other body parts with a hard matrix is teeth
So the extracellular matrix = Collagenous fibres and calcified matrix
What 2 parts are the skeleton split into?
Axial Skeleton
Appendicular Skeleton
How many bones in Axial skeleton and what is its function?
80
The main supporting/foundation bones
The bones down the middle
Examples of bones in the Axial skeleton
Bones of skull
RIbs
Vertebrae
How many bones in the Apendicular Skeleton and its function
126
All other bones not in Axial Skeleton
Needed to help movement
Examples of Appendicular Skeleton bones
Upper Limbs
Lower LImbs
Pelvic Girdle
What are the 2 forms of Bone?
Compact/dense (Cortical Bone)
Spongy (Cancellous or medullary Bone)
Where is Compact/Cortical bone found?
Shafts of long bones
Forms plates of flat bones
Where is spongy bone found?
Ends of long bones (In epiphyses)
Centre of flat bones
Centre of Irregular Bones
What is found in central cavity and in spaces of spongy bone in Long Bones?
Red bone marrow (Haemopoiesis)
Yellow bone marrow ( Adipose tissue for energy source)
What is special about yellow bone marrow?
It can convert to red bone marrow in times of severe stress
What is Periosteum?
The tough DENSE vascular fibrous connective tissue layer that surrounds the bone.
It supplies blood (nutrients),lymphatic vessels and nerves to the Osteons via the Haversian canal
What is the Endosteum?
Thin cellular layer lining the inside of the marrow cavity of the bone
What is the function of Cortical bone?
Provides mechanical strength and protects organs
Spongy Bone function and where is it found?
End of long bones and centre of flat and irregular bones
Gives space for red marrow to grow and develop
What is the strucutre and function of the Central cavity of long bones?
Has spaces of spongy bone (yellow marrow can be here)
What is the Epiphyses in long bone?
The ends of the bone containing Cancellous or spongy bone
What is the diaphyses in long bone?
The hollow region of bone made up of cortical bone found between the 2 epiphyses, contains Bone marrow
What is an osteoblast?
Bone producing cell
It lays down substance called osteoid
What is osteoid?
Collagen 1
Enzymes
Ground substance
What is an Osteocyte?
An osteoblast which has been surrounded in MINERALISED OSTEOID = BONE SUBSTANCE
What is an osteoclast?
Multinucleated cell that contains macrophages which breaks down bone.
What is an Osteon/Haversian system?
Osteon and Haversian system are interchangeable terms
The Functional Unit of the Cortical Bone
The Structures that cortical bone is composed of
What is Lacunae?
Spaces which contain osteocytes