Chapter 5 – Vertebrate Anatomy BONES Chapter 5 – Vertebrate Anatomy

Major Functions of Bone Support Backbone, etc. Protection Skull, ribs Movement Levers against which muscles work Mineral storage Blood cell formation

Two Major Types of Bone Compact Bone Spongy Bone

Compact Bone Dense Smooth and solid in appearance

Spongy Bone Honeycombed Contains marrow in spaces

Bones are Classified by Shape Long Bones Short Bones Flat Bones Irregular Bones

Long Bones Bones that are longer than they are wide. Shaft with two ends Primarily compact bone Spongy bone at interior All bones of the limbs are long bones

Short Bones Roughly cubelike in shape Contain mostly spongy bone Bones of the wrist and ankle

Flat Bones Thin, flattened and usually a bit curved Two roughly parallel compact bone surfaces with spongy bone within Skull bones; scapulae (shoulder blades)

Irregular Bones Bones that fit none of the other classes Vertebrae Hip bones (pelvic bones) These bones have complex shapes Consist mainly of spongy bone

Bones are Organs Bones are supplied and associated with many other tissues, thus they are organs Supplied with nerves, blood vessels, lymph vessels Covered with membranes (epithelial tissues)

Structure of a Typical Long Bone Diaphysis – shaft of the long bone Thick collar of compact bone surrounds a central marrow cavity Epiphysis – ends of a long bone Exterior of epiphyses are formed by compact bone interior contains spongy bone Joint surface of each epiphysis is covered with articular cartilage Epiphyseal line Remnant of a structure called the epiphyseal PLATE Epiphyseal plate is the disk-like plate which allows for growth of the long bone during childhood Cushions opposing bone ends during movement

Epiphysis detail Click here for a detailed view of the epiphysis

Structure of Long Bone, cont. Both internal and external surfaces are covered with membranes Outer membrane – periosteum Covers shaft Richly supplied with blood vessels, nerves, etc. Vessels enter through holes in the bone called nutrient foramen Membrane also is anchoring point for tendons and ligaments Inner membrane - endosteum

Structure of Short, Irregular and Flat bones Simple design Outside – compact bone Inside – spongy bone

Blood forming tissue in bones Red marrow Typically found in cavities of spongy bone in long bones and flat bones In adults, most blood formation occurs in Head of femur/humerus Sternum Hip bones In adults, the marrow cavity containing yellow marrow (fat) extends well into the epiphyses of most long bones

Chemical Composition of Bone Both inorganic and organic compounds make up bone Proper combination of organic and inorganic components allows bones to be durable without being brittle Organic components Composed of Cells Organic portion of matrix Provide flexibility and tensile strength (strength under tension) Inorganic components Mineral salts Calcium phosphate is the main mineral salt Provide hardness

Bone Markings Bones have many bumps, bulges, depressions, holes, etc. “Bumps” are typically are points for muscle attachment Holes are typically points for blood vessels or nerves to pass through

Terms for Bone Markings Condyle – smooth rounded projection that allows for articulation Articulation – usually a place where two bones meet and move against each other, but sometimes no movement occurs. The image shows the occipital condyles at the base of the skull. These articulate with the first vertebra.

Terms for Bone Markings Crest A narrow ridge of bone The images show the sagittal crest of a badger

Terms for Bone Markings Foramen A hole Usually for passage of blood vessels and/or nerves

Terms for Bone Markings Process Any bony prominence or projection To the right is the mastoid process Also visible is the styloid process Both are sites of muscle attachment to the skull

Terms for Bone Markings Spine A sharp slender process or projection This photo shows the neural spines on vertebrae of a dinosaur

Terms for Bone Markings Suture A seam Irregular lines produced by interlocking bones An immovable joint The photo shows sutures of the skull

Terms for Bone Markings Fossa A depression Often an articulating surface May meet with a condyle on another bone

Types of Fractures Simple – only bone damage – little or no tissue damage Complete break

Types of Fractures Compound – bone breaks through the soft tissue to the outside High risk of infection

Types of Fractures Compression This type of bone fracture generally occurs after a fall where the vertebral column is compressed and then under the extreme pressure cracks or breaks. Crushing of bone

Types of Fractures Comminuted – more than two fragments of bone broken off.

Types of Fractures Impacted Ends of bone become wedged together

Types of Fractures Spiral Fracture caused by twisting force that creates an oblique fracture around and through the bone

Types of Fractures Greenstick incomplete fracture in which only one side of the bone has been broken.

Types of Fractures Depression

Homeostatic Imbalances of Bone Osteoporosis Diseases in which bone resorption outpaces bone replacement Bone marrow becomes porous and lighter Spine is most vulnerable; also neck of femur Estrogen and testosterone are important in maintaining normal bone density After menopause, estrogen secretion in women diminishes and contributes to bone loss Other causes of bone loss Lack of exercise smoking

Preventing Osteoporosis Take calcium beginning at age 35-40 Drink flouridated water Do weight bearing exercise

Other diseases of bone Osteomalacia Rickets Bones inadequately mineralized Rickets Bones bend/deform Children mostly affected Caused by low calcium; vitamin D