Post on 13-Dec-2015
Skeletal System
Inside look at the BONES
Image from: www.interactive-biology.com
Parts of the Skeletal System
Bones (Skeletal
organ)
Joints
Cartilage
Ligaments
Tendons
Types of BonesBones are classified by their structure each vary
in proportions of compact and cancellous. Long Short Flat Irregular Sesamoid
Short, Flat, Irregular, Sesamoid Short
Cube or boxed shaped Examples: Carpals and Tarsals
Flat Broad and thin with flattened and curved surface Filled with marrow Example: Sternum
Irregular Misshaped bones found in groups Examples vertebral and facial bones
Sesamoid Found in locations where a tendon passes a joint Example: patella
Long BonesKnown for its length and
distinct structures Diaphysis
Main shaft of a long bone Hollow, cylindrical shape and thick
compact bone Function is to provide strong
support without cumbersome weight
Epiphyses Both ends of a long bone; made of
cancellous bone filled with marrow Function is to provide
attachments for muscles and give stability to joints
Long Bone (continued) Articular cartilage
Layer of hyaline cartilage that covers the articular surface of epiphyses
Function is to cushion jolts and blows
Periosteum Dense, white fibrous
membrane that covers bone Attaches tendons firmly to
bones Contains blood vessels essential for bone cell
survival and bone formation
Long Bone (continued) Medullary (or marrow) cavity
Tubelike, hollow space in the diaphysis
Filled with yellow marrow in adults
Endosteum: Thin, fibrous membrane that lines the
medullary cavity
Sharpey’s fibers Secure periosteum to underlying bone
Arteries Supply bone cells with nutrients
Distal
epiphysis
Proximal
epiphysis
diaphysis
yellow marrow
epiphyseal line
periosteum
compact bone
spongy bone
Endosteum
hyaline cartilage
Sharpey’s fibers
Anatomy of the Long Bone
Bone Tissues Most distinctive form of connective tissue Composition
Inorganic salts ( calcium, phosphate, magnesium and sodium)
Organic matrix (collagenous fibers, proteins and polysaccharides, glucosamine)
Two basic types Compact Bone Spongy Bone
Compact Bone Contains many cylinder-shaped
structural units called osteons, or haversian systems
Osteons surround haversian canals that run lengthwise through bone and are connected by transverse (Volkmann) canals
Living bone cells are located in osteon
Osteons permit delivery of nutrients and removal of waste products
Structures of Osteon Lamella- concentric calcified
matrix
Lacunae- spaces filled with tissue fluid between lamella
Canaliculi- ultra small canals that connect lacunae and harvesian canals
Harvesian canals- contain blood vessels and lymphatic vessels
Gray’s Anatomy of the Human Body from the classic 1918 publication
Cancellous (Spongy) Bone No osteons in
cancellous bone; it has trabeculae instead
Nutrients are delivered and waste products removed by diffusion through tiny canaliculi
Bony branches (trabeculae) are arranged along lines of stress to enhance the bone’s strength
Types of Bone Cells Osteocytes
Mature bone cells
Osteoblasts
Bone-forming cells
Osteoclasts
Bone-destroying cells
Break down bone matrix for remodeling and release of calcium
Bone remodeling is a process by both osteoblasts and osteoclasts
Blood supply
Bone cells are metabolically active and need a blood supply
Supplied from bone marrow
Bone marrow and blood vessels penetrates the bone and then, by way of transverse (Volkmann) canals, connects with vessels in the central canals of osteons
Bone Marrow Composition
Myoloid- soft connective tissue
Function Site of for production of
blood cells; hematopoises Location
Medullary cavities of long bones
Empty spaces of spongy bone
Types of Marrow Red marrow
Found in virtually all bones in an infant’s or child’s body Produces red blood cells
Yellow marrow As an individual ages, red marrow is replaced by yellow
marrow Marrow cells become saturated with fat and are no longer
active in blood cell production
Bones Function Support- form the framework that supports
the body and cradles soft organs.
Protection- provides a protective case for brain, spinal cord and vital organs
Movement- provides levers for muscles
Mineral Storage- reservoir for minerals especially calcium
Blood cell formation- hematopoiesis occurs in the within the marrow cavities of the bones
Calcium levels 98% calcium in the body is found in bones
Calcium levels change as a result of bone remodeling.
Homeostasis of calcium ion concentration affects several functions Bone formation, remodeling and repair Blood clotting Trasmission of nerve impulses Cardiac and skeletal muscle contractions
Mechanism of Calcium Homeostasis Parathyroid
hormone Primary regulator
of calcium homeostasis
Calcitonin Protein hormone
produced in the thyroid gland
Produced in response to high blood calcium levels
Bone Development Osteogenesis
development of bone small cartilage model to adult model
Endochondral ossification Bone formation
spreading essentially from the center to the ends
Replacement of hyaline cartilage
From cartilage to bone Cartilage cells (chondrocytes) begin to die, region
becomes known as the ossification center Primary- middle of diaphysis Secondary- epiphysis
Periosteum is forming around the outside of the cartilaginous model.
Periosteum produces osteoblast Osteoblasts build up on the periphery of the
spongy bone, they secrete their matrix and build compact bone all around the spongy bone.
This occurs simultaneously
The Growing Bone Epiphyseal plate
remain between diaphysis and both epiphysis.
Its is composed of 4 layers “Resting” cartilage cells- Zone of proliferation- cartilage
cells undergoing mitosis Zone of hypertrophy- older
cells undergoing degenerative changes
Zone of Calcification- dead cartilage cells undergoing calcification
Osteoclast widen the medullary cavity
Osteoblast build new bone around existing bone
Cartilage Characteristics
Avascular connective tissue Fibers of cartilage are embedded in a firm gel Has the flexibility of firm plastic No canal system or blood vessels
Functions Tough, rubberlike nature permits cartilage to
sustain great weight or serve as a shock absorber Strong yet pliable support structure Permits growth in length of long bones
Types of Cartilage Hyaline cartilage
Most common type Covers the articular surfaces of bones
Elastic cartilage Forms external ear, epiglottis, and eustachian
tubes Fibrocartilage
Occurs in pubic symphysis and intervertebral disks Strong and rigid
Bone Fractures Fracture—break in a bone
Types of bone fractures Closed (simple) fracture—break that does not
penetrate the skin Open (compound) fracture—broken bone
penetrates through the skin
Bone fractures are treated by reduction and immobilization
Common Types of Fractures
Table 5.2
Bone repair Healing
1. Fractures destroy blood vessels
2. Vascular damage initiates repair
3. Dead bone is removed by osteoclastic resorption
4. Fracture hematoma(blood clot cause duiring break) is
reabsorbed and callus ( Specialized repair tissue) is
deposited in bones