Bones H.Smith

BoneTissue Question…are bones alive?

Bones are tissues Tissues are made up of… There are 4 types of bone cells Osteo means..

1. Osteoblasts Found within bones Function: make new bone tissue

2. Osteocytes Made by Osteoblasts; mature bone cells Surrounded by bone as they are made Function: maintain bone as a living tissue

3. Osteoclasts Formed in the bone marrow (Related to WBC) Function: Dissolve & absorb old bone tissue

4. Hematopoietic Found in bone marrow Function: produce blood cells

Bone maintenance Bone is constantly being broken down & rebuilt. What cells break it down? What cells rebuild it?

Bone tissue organization

Compact Bone Found on the outside of bones Composed of osteons Covered by the periosteum: membrane that acts as attachment points for muscles.

Closer look at Osteons; AKA Haversian system Central tube: nerves & blood supply Lamellae: rings made of calcium & collagen (provide hardness!) Lacunae: small spaces between lamellae Home of osteocytes Canaliculi Tiny channels between lacunae, function to allow nutrients to the osteocytes & wastes to leave them

Compact bone & osteons

Now You Practice

Lets review: 4 types of bone cells:

Let’s review How is bone maintained?

Let’s review: Compact bone is found…. Compact bone is made up of…. Compact bone is covered by…

Let’s review: 4 parts of an osteon

Inside compact bone is…Spongy bone

Spongy Bone Provides strength to weight bearing bones Protects the bone marrow (hematopoietic cells)

Function of Bones Support Bones provide a hard framework that supports the body Bones provide support for internal organs

Function of Bone Protection Skull protects the brain Spinal cord is surrounded by vertebrae Rib cage protects vital organs

Function of Bone Movement Skeletal muscle attached to bones use the bones as levers to move the body Arrangement of bones and joints determine the movements possible

Function of Bones Mineral Storage Bone serves as a mineral reservoir Phosphate and calcium ions can be released into the blood steam for distribution Deposition and removal are ongoing

Function of Bones Blood cell formation Hematopoiesis occurs within the marrow cavities of the long bones The majority of hematopoiesis occurs in bones

Ossification Cartilage is covered by bone & internal hyaline cartilage is broken down

Epiphyseal Plates Site of bone growth in length

Bone Growth Through Adolescence Controlled by growth hormone, and after puberty, sex hormones Longitudinal growth – occurs at epiphyseal plates Completely ossified by end of adolescence

Bone Remodeling Constant osteoblast & osteoclast activity throughout life Causes: Ca+2 levels in blood If too low, parathyroid hormone activates osteoclasts If higher than needed, calcitonin (a hormone) activates osteoblasts Pull of gravity & muscles Activates osteoblasts If not active, activates osteoclasts – atrophy Partial reason for some bed-ridden individuals

Fractures Reduction – realignment of bone ends AKA “resetting” 4 Stages of healing

Bone Healing 1. Fracture hematoma – blood from broken vessels forms a clot. – 6-8 hours after injury – swelling and inflammation

2. Fibrocartilaginous callus lasts about 3 weeks -Chondroblasts create a cartilage callus around the fracture

3. Bony callus (after 3 weeks and lasts about 3-4 months) – osteoblasts replace cartilage with bone

4. Bone Remodeling Osteoclasts remodel bone into compact bone and spongy bone – Often no trace of fracture line on X-rays.

Cool facts about bone breaks: Your body is so good at healing broken bones, it can be impossible to detect a fracture line after a full recovery. Collarbone is most commonly broken among children. Overall most common break is the wrist (before 75 years of age) and the hip (after 75 years of age)

Common Types of Fractures

Review Which cell type forms new bone? Which cell type destroys bone? Which cell type is a mature bone cell? What is the name of the “space” that a mature bone cell is enclosed within? What kind of tissue are fetal bones made of? What is ossification? What is the site of longitudinal bone growth called?

Which hormones control bone growth through adolescence? Which hormones control bone remodeling? What does each one do? If a doctor reduces a fracture, what is she doing?