Module 6: Bones and Skeletal Tissue Flashcards
5 Types of bones
Long Short Sesamoid Flat Irregular
Long Bones
Longer than they are wide
Ex. Femur (thigh), Humerus (upper arm)
Short Bones
Cube shaped
Ex. wrist, ankle
Sesamoid Bones
Shaped like a sesame seed
Type of short bone within a tendon
Ex. Patella (kneecap)
Flat Bones
Thin, flat, curved
Ex. Skull bones, sternum
Irregular Bones
Irregular shapes that do not fit into other 4 categories
Ex. Vertebrae, some skull bones, hip bones
Functions of the skeletal system (4)
Support
Protection
Movement
Mineral Storage
Hematopoiesis
Blood cell formation
Takes place in the red marrow of bones
Osseous
Bone tissue
Most rigid of connective tissues
Hard matrix of mineral salts (for rigidity) deposited around protein fibres (for elasticity and strength)
Bone cells (3)
Osteoblasts
Osterclasts
Osteocytes
*At any time, osteoclasts are removing matrix and osteoblasts are adding to it
Osteoblasts
Immature bone cells
May develop into osteocytes
Responsible for production of new bones
Produce the matrix of the bone
Osteocytes
Mature bone cells
Embedded in the matrix
Help repair damaged bone
Most numerous of the 3 types in adults (bones are no longer growing)
Osteoclasts
“demolition” cells
Maintain the density and composition of the bone by removing Ca salts in the surrounding matrix
Essential for bone remodelling and growth
Release stored minerals in the bones tissue into body fluids
If osteoblasts add to matrix faster than osteoclasts remove it,
the bones grow thicker and stronger
If osteoclasts remove matrix faster than osteoblasts deposit it,
the bones grow thinner and weaker
2 types of bone tissue
Compact and spongy (cancellous)
Compact bone
Dense, hard tissue
Replaced every 10 years
Found in shafts of long bones and outer surfaces of other bones
Microscopic units of compact bone called Osteon (Haversian system)
Osteon (Haversian System)
In compact bone, consists of the following:
Central canal (Haversian canal)
Lamellae (circular rings of matrix)
Lacunae (osteocyte pockets)
Canaliculi (interconnecting channels)
Volkmann’s Canals
Associated blood vessels and nerve tissue
Central canal
AKA Haversian Canal
contains blood vessels and nerve cells
Lamellae
Form circular rings of matrix; osteocytes are located between these circular rings
Lacunae
“little lakes”
Pockets that Osteocytes sit in
Lacunae are found between thin sheets of calcified matrix
Canaliculi
Interconnecting channels
Responsible for joining the Lacunae with each other
Can also link lacunae to nearby blood vessels
Volkmann’s Canals
AKA Perforating canals
Connect the blood and nerve supply of the periosteum to those in the central canals and medullary cavity
Spongy (cancellous) bone
Less dense than compact bone Replaced every 3-4 years Ends of long bones and in the center of other bones Does not contain osteons Arranged in trabeculae
Trabeculae
Spongy bone arranged in planes
Make spongy bones look like swiss cheese
Spaces within the bones formed by trabecular decrease the weight of the bone and provide the spaces where red bone marrow is found
Parts of a Long Bone (7)
Diaphysis Epiphyses Epiphyseal plate Medullary cavity Endosteum Periosteum Articular cartilage
Diaphysis
Long shaft of long bone
Composed mostly of compact bone
Epiphyses
Enlarged ends of a long bone
Covered by Articular (hyaline) cartilage
Epiphyseal Plate (disk)
Band of hyaline cartilage between the epiphysis (enlarged ends) and the diaphysis (long shaft)
Medullary Cavity
Hollow centre of the diaphysis
Filled with red bone marrow in infants (for production of blood cells)
Filled with yellow bone marrow in adulthood (for fat storage)
Endosteum
Connective tissue that lines the medullary cavity
Periosteum
Tough membrane made of fibrous connective tissue
Covers the outside of the bone (except at joint surfaces)
Protects the bones
Point of attachment for muscles
Contains blood vessels that nourish the underlying bone tissues
Articular Cartilage
“joint cartilage” that is found on the outer surface of an epiphysis
Smooth, shiny surface provides movement in the joints by helping to decrease friction
Ossification
Bone formation
Begins 6wks after fertilization (embryo is 1/2” long)
Continues to grow through adolescence
Some parts of skeleton do not stop growing until age 25
2 ways bones form
- flat, skull bones are formed when osteoblasts replace thin connective tissue membrane with bone tissue
- All other bones are formed when osteoblasts replace hyaline cartilage with bone tissue
Bone growth in Length
Takes place is epiphyseal plate
Growth hormone = stimulates growth at plate
Estrogen and testosterone = cause epiphyseal plate to seal and inhibit further growth in length
When growth stops, epiphyseal plate ossifies (hardens) so that only a thin epiphyseal line remains
Bone growth in width and thickness
Coordinated between osteoblasts and osteoclasts
Osteoblasts in periosteum form compact bone around external bone surface
Osteoclasts in the endosteum break down bone on the internal bone surface around the medullary cavity
Wolff’s Law
suggests that a bone will grow or remodel in response to stresses, muscle activity, repair of bone fractures, excess body weight, etc.
Types of fractures (7)
Complete Incomplete Open (aka compound) Closed (aka simple) Transverse Comminuted Oblique
Complete fracture
break across entire section of bone
Incomplete fracture
Break almost extends across entire section of bone
Still has some bone partially joined together (greenstick)
Open fracture (Compound)
Broken end of the bone protrudes through skin
Can pose skin problems (open pathway provides a site for infection to enter the body)
Closed fracture (Simple)
Broken bone does not extend through the skin; less chance of bacterial invasion
Transverse fracture
Bone is broken at right angle to the long axis of the bone
Comminuted fracture
Bone is crushed into small pieces
Oblique fracture
Bone is broken on a slant
Repair of fracture
1) closed reduction or open reduction
2) healing
Closed reduction
manipulation of a fracture into normal alignment
Open reduction
Surgery is necessary to bring fractured bone fragments into normal alignment
Healing process is slow because (2)
- blood supply to broken part of bone and surrounding damaged tissues has been interrupted (causes reduction in supply of nutrients necessary for cellular metabolism and mitosis of all cells involved in the fracture)
- Mitosis is a normally slow process for bone cells (naturally)
