Chapter 5 Skeletal System

Functions of Bone - How do bones contribute to homeostasis? -Protection -Support -Movement -Storage- store fat & minerals -Blood cell formation- blood cells are formed

within the marrow cavities of certain bones

Anatomy of Bone

Types of Bone

Compact Bone: -Dense -Smooth

Spongy Bone: -Composed of small pieces of bone

-Lots of space

All bones fall under these two basic types:

How many bones make up our skeleton?!?-206!

Types of Bone

Long Bone Flat Bone -thin, flattened

-usually curved

-made up of layers of spongy bone squished between 2 compact bones

-longer then they are wide -mostly compact bone

After a bone is classified as either compact or spongy they are further classified according to their shape-4 types of shape:

Types of Bone Cont’d Irregular Bone

Short Bone-bones that don’t fit into the other categories

-cubed shaped -mostly spongy bone

Classification of Bones- Take a few minutes to classify the bones of the skeleton

Closer look at long bones

-important structures of long bone: in the picture your femur

-diaphysis-periosteum-epiphyses-articular cartilage -epiphyseal line -epiphyseal plate

Closer look at long bones

-important structures of long bone:

-diaphysis: AKA the shaft-makes up the bone’s length -covered in protective fibrous connective tissue called periosteumepiphyses: ends of long bone-covered by protective cartilage, articular cartilage

Closer look at long bones

-important structures of long bone:

-epiphyses: 2 ends of the bone-proximal epiphyses

-remember what proximal means?

-closer to trunk/torso-distal epiphyses

-distal is the opposite, further away from the trunk/torso

Closer look at long bones

-important structures of long bone:

-epiphyseal line: found in adult bones -remnant of epiphyseal plate

-which is seen in young growing bones

-cause growing of long bones

-end of puberty hormones stop growth of long bones, the plate is replaced by bone leaving a line to mark its location

Microscopic look at long bones

-important structures of compact bone that is only visible under a microscope:

-riddled with passageways carrying nerves, blood vessels & provide living bone cells with nutrients -osteocytes: mature bone cells

-found in tiny cavities within the matrix called lacunae

-lacunae arranged in circles called lamellae around central canals

-each complex contains a central canal & matrix rings are known as osteon or Haversian system

-osteocytes: mature bone cells -found in tiny cavities lacunae

-lacunae arranged in circles called lamellae around central canals

-each complex contains a central canal & rings are called osteon or Haversian system

Red & Yellow Bone Marrow Yellow Marrow -middle cavity of a long bone

shaft stores yellow marrow, AKA medullary cavity -made of adipose fat tissue

Red Marrow -in infants middle cavity forms

blood cells & red marrow -in adults red marrow is confined

to the cavities in spongy none - Found in flat bones (ribs,

vertebrae, pelvic bones)

Hyaline Cartilage Abundant cartilage fibers hidden by a rubbery matrix with glassy blue-white appearance

Bone Growth and Formation

Babies -Embryo: hyaline

cartilage -Infant: cartilage

replaced by bone

Fibrous membranes connecting flat bones

Adults -Almost entirely

bone -Isolated cartilage

remains (nose, ear, etc)

Flat bones replace connective membranes

Bone Growth and Formation -bones use cartilage as “models” during bone formation (ossification)

-ossification happens in two steps: 1.Hyaline cartilage model is superficially covered

with bone matrix by osteoblasts 2.Hyaline cartilage is broken down, leaving

behind an empty, medullary cavity.

Ossification

Ossification Cont’d After birth, only two regions of cartilage remain: articular cartilages and epiphyseal plates

-articular cartilage covers ends of long bones

https://www.youtube.com/watch?v=p-3PuLXp9Wg

Bone Remodeling Bones change as the body grows. Why is this necessary?

As the body changes in size and weight, our bones must compensate for the additional mass.

Additionally, bones become thicker & form projections where bulky muscles attach

Bone Remodelingoccurs in response to two factors: Blood Calcium Levels

- Healthy balance must exist between Ca stored and excreted

-Proper [Ca] is controlled by endocrine system

Calcitonin- storing calcium

Parahormone- release calcium into bloodstream

Pull of gravity and muscles on the skeleton

Determines where skeleton is remodeled

Axial & Appendicular Skeleton

Axial Skeleton: -divided into 3

parts: -skull -vertebral

column -bony thorax

Appendicular Skeleton: -composed of

126 bones of the limbs

-pectoral & pelvic gridle

Our skeleton is divided into two parts:

Axial Skeleton Skull, vertebral column, bony thorax

Appendicular Skeleton Bones of the limbs and girdles

Joints in our body Place where two bones come together

Classified by the amount of movement they allow

-immovable

-slightly movable

-freely movable

Joints in our body 4 types of joints in our body:

1. Hinge- only one single action is allowed

-similar to opening & closing a door Ex:

-our elbow & fingers

2. Ball & socket- rounded curved shape surface of one bone fits into concave, cup shaped surface of another bone

-allows for 360 degree movementEx:

-our hip & shoulder bone

Joints in our body 4 types of joints in our body:

3. Pivot- movement occurs in a half circle, rotation of one bone around another

Ex:

4. Plane/gliding- surfaces are flat, only sliding & twisting movements are allowed without any circular movement

Ex:

-carpals in our wrist, tarsals in our ankle

-joint between the axis & atlas of neck

Healing a Bone Occurs in 4 Steps: 1.Hematoma is formed 2.Break is splinted by fibrocartilage 3.Bony callus is formed 4.Bone remodeling occurs