Post on 12-Jan-2016
Chapter #6: Bones and Skeletal Tissues
Skeletal Cartilages
Found in adults where flexible skeletal tissue is needed
Contains no blood vessels or nerves Surrounded by the perichondrium
(dense irregular connective tissue) that resists outward expansion
Three types – hyaline, elastic, and fibrocartilage
Hyaline Cartilage
Provides support, flexibility, and resilience
Only contains fine collagen fibers Is the most abundant skeletal
cartilage Includes these types:
Articular – covers the ends of long bones
Costal – connects the ribs to the sternum
Respiratory – makes up larynx, reinforces air passages
Nasal – supports the nose
Elastic Cartilage
Similar to hyaline cartilage, but contains elastic fibers
Found in the external ear and the epiglottis
Fibrocartilage
Highly compressed with great tensile strength
Found where there is heavy pressure and stretch
Found in menisci of the knee and in intervertebral discs
Growth of Cartilage
Appositional “growth from outside” - cells in the perichondrium secrete
matrix against the external face of existing cartilage
Interstitial “growth from inside” – lacunae-bound chondrocytes inside the
cartilage divide and secrete new matrix, expanding the cartilage from within
Calcification of cartilage occurs During normal bone growth During old age
Classification of Bones 206 bones of the body are divided into two
groups:
1. Axial skeleton “long axis of the body”
- bones of the skull, vertebral column, and rib
cage - mostly involved in protecting,
supporting or carrying other body parts
2. Appendicular skeleton – bones of the upper and lower limbs
& girdles (shoulder and hip) - primarily for locomotion
Axial and Appendicular Skeleton
Classification of Bones: By Shape Long bones –
longer than they are wide (e.g., humerus)
Short Bones -cube shaped
bones of the ankle and wrist
Sesamoid Bone - special type of
short bone - bones that form
within tendons (patella)
Flat Bones - thin, flattened
and a bit curved (sternum and most skull bones)
Irregular Bones - bones with
complicated shapes (vertebrae and hip bones)
Functions of Bones
Support – form the framework that supports the body and cradles soft organs
Protection – provide a protective case for the brain, spinal cord, and vital organs
Movement – provide levers for muscles
Functions of Bones cont….
Mineral storage – reservoir for minerals, especially calcium and phosphorus
Blood cell formation – hematopoiesis occurs within the marrow cavities of bones
Bone Structure Bones are considered organs b/c
they are made up of many types of tissues:
* mostly osseous tissue * nervous tissue in their nerves * cartilage in their articular
cartilages * fibrous connective tissues lining
cavities * muscle and epithelial in their
blood vessels
Bone Structure
Gross Anatomy of a Bone
A. Bone Markings - Bulges, depressions, and holes that serve
as: Sites of attachment for muscles, ligaments, and
tendons Joint surfaces Conduits for blood vessels and nerves
Named in different ways:
1. projections (bulges) - grow outward from the surface - those that are sites of muscle and ligament
attachment include: Tuberosity – rounded projection Crest – narrow, prominent ridge of bone Trochanter – large, blunt, irregular surface Line – narrow ridge of bonee – sharp, projection Process – any bony prominence Tubercle – small rounded projection or process Epichondyle – raised area on or above a condyle Spine – sharp, slender, often pointed projection
- Projections that help to form joints include:
Head – bony expansion carried on a narrow neck
Facet – smooth, nearly flat articular surface
Condyle – rounded articular projection Ramus – armlike bar of bone
2. Depressions and openings - serve as a passage for nerves and blood vessels - include the following: meatus – canal like passageway Sinus – cavity within a bone, filled with air and lined with mucous membrane Fossa – shallow, basinlike depression in a bone, often serving as an articluar
surface Groove – furrow Fissure – narrow, slitlike opening Foramen – round or oval opening through a
bone
Gross Anatomy cont….B. Bone Textures 1. Compact bone – dense outer layer/
looks smooth and homogeneous
2. Spongy bone – composed of small, needlelike
pieces of bone called trabeculae and lots of
open space
C. Structure of a Long Bone
Long bones consist of a: - diaphysis - epiphysis
Diaphysis - Tubular shaft that forms the axis of long bones - Composed of compact bone that surrounds the medullary cavity - Yellow bone marrow (fat) is contained in the medullary cavity
Epiphyses - expanded ends of long bones - exterior is compact bone, and the
interior is spong bone - joint surface is covered with articular
(hyaline) cartilage - e piphyseal line separates the
diaphysis from the epiphyses
Structure of a Long Bone
D. Bone Membranes
1. Periosteum - double-layered protective membrane covering the diaphysis
- outer fibrous layer is dense regular connective
tissue
- inner osteogenic layer is composed of
osteoblasts and osteoclasts
-Richly supplied with nerve fibers, blood,
and lymphatic vessels, which enter the
bone via nutrient foramina
- Secured to underlying bone by hundreds of
connective tissue fibers called Sharpey’s
fibers
2. Endosteum – delicate membrane covering internal
surfaces of bone
E. Structure of Short, Irregular, and Flat Bones Thin plates of periosteum-covered
compact bone on the outside with endosteum-covered spongy bone (diploë) on the inside
Have no diaphysis or epiphyses Contain bone marrow between the
trabeculae
Microscopic Anatomy of a Bone
Four major cell types found in bone tissue:1. osteogenic “osteoprogenitor cells”
2. osteoblasts: bone forming cells 3. osteocytes: mature bone cells 4. osteoclasts: large cells that
reabsorb or break down
bone matrix
(Organic components of Bone)
Inorganic Components of Bone Include:
Hydroxyapatites, or mineral salts Sixty-five percent of bone by mass Mainly calcium phosphates Responsible for bone hardness and its
resistance to compression
Compact Bone Anatomy A. Osteon (Haversian System):
structural unit of
compact bone
Osteon Structure includes:
Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
Haversian, or central canal – central channel containing blood vessels and nerves
Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
B. Osteocytes – mature bone cellsC. Lacunae – small cavities in bone that
contain osteocytes
D. Canaliculi – hairlike canals that connect
lacunae to each other and the
central canal