skelatal system

What is the skeletal system?

The skeletal system is made up of bones, cartilage, ligaments, and connective tissues that hold the body together.

What is the skeleton?

The skeleton is a scaffolding made of bones.

What are the two main functions of the skeleton?

Support the soft tissues of the body and protect the soft tissues and organs of the body.

What do the terms os and osteo refer to?

Bones.

What is an example of a word containing osteo?

Osteocyte, which is a bone cell.

How hard is bone compared with other substances in the body?

Bone is the second hardest substance in the body; only tooth enamel is harder.

What cells produce bone?

Osteoblasts.

What do osteoblasts secrete?

They secrete the matrix of bone.

What process causes the bone matrix to harden?

Ossification.

What happens to osteoblasts after ossification?

They become osteocytes.

What is the function of osteocytes?

They maintain bone tissue.

What is necessary for a broken bone to heal?

The broken ends must be brought together into alignment and held still for a few weeks to months.

How many main functions of bones are identified?

Five.

What are the five main functions of bones?

Support, protection, leverage, storage, and blood cell formation.

What is the most basic function of the skeletal system?

Support.

Why do bones provide support?

Body tissues are soft and weak, so bones act as a framework to support the tissues and body.

How do bones protect the body?

Their firm strength protects delicate organs and tissues by completely or partially surrounding them.

What does the skull protect?

The brain.

What do the ribs protect?

The heart and lungs.

How do bones provide leverage?

They act as levers for skeletal muscles, allowing the body to move.

What attaches skeletal muscles to bones?

Tendons.

What mineral do bones store?

Calcium.

How do bones help regulate calcium?

They act as reserve banks, allowing calcium to be deposited into or withdrawn from bone to control blood calcium levels.

What functions does calcium have in the body?

Muscle contraction, blood clotting, milk secretion, skeleton formation, and skeleton maintenance.

What is hematopoiesis?

Blood cell formation.

Where does hematopoiesis occur?

In the marrow that fills certain bones.

What are the two main types of bone?

Cancellous bone and compact bone.

What is cancellous bone?

Light and spongy bone; also called spongy bone.

What is compact bone?

Dense, heavy, and strong bone.

What is the periosteum?

A membrane covering the outer surfaces of bones.

Where is the periosteum not found?

On the articular or joint surfaces of bones.

What are the two layers of the periosteum?

An inner layer and an outer layer.

What is found in the inner layer of the periosteum?

Osteoblasts.

What is the function of the inner periosteal layer?

It is involved in healing fractures.

What is the outer periosteal layer made of?

Fibrous tissue.

Why is cancellous bone called spongy bone?

Because it has an appearance similar to a sponge.

What fills the spaces in cancellous bone?

Bone marrow.

Is cancellous bone weak?

No. It is light but very strong.

Where is compact bone found?

In the shafts of long bones and in the outer layer of all bones.

What are the three types of bone cells?

Osteoblasts, osteocytes, and osteoclasts.

What do osteoblasts do?

They form bone by secreting the bone matrix and supplying minerals needed to harden it.

What do osteoblasts eventually become?

Osteocytes.

What do osteocytes do?

They maintain bone tissue and can revert back into osteoblasts to form new bone after injury.

What do osteoclasts do?

They break down bone.

Why are osteoclasts important?

They remove bone where it is not needed and are necessary for bone remodeling.

How do osteoclasts help regulate calcium?

They allow calcium to be withdrawn from bone when blood calcium levels become too low.

What is the easiest way to remember osteoblast?

Blast = builds bone.

What is the easiest way to remember osteoclast?

Clast = breaks down bone.

What is the metaphysis?

The narrow portion of a long bone between the epiphysis and diaphysis.

What is located in the metaphysis?

The growth plate.

What happens to the growth plate as a bone grows?

It gradually ossifies near the diaphysis and epiphyses.

How does blood reach bone?

Tiny blood vessels penetrate the periosteum.

What are Volkmann's canals?

Channels that carry blood vessels from the periosteum into the bone and communicate with Haversian canals.

What are Haversian canals?

Channels that surround blood vessels and nerve cells throughout bone.

What do Haversian canals communicate with?

Osteocytes through canaliculi.

What are canaliculi?

Small channels that allow communication between Haversian canals and osteocytes in the bone matrix.

What are nutrient foramina?

Large holes through which large blood vessels, lymph vessels, and nerves enter larger bones.

What is the main function of nutrient foramina?

They primarily carry blood into and out of the bone marrow.

Why are nutrient foramina important on radiographs?

They can resemble crack-type fractures.

What do Volkmann's canals connect?

Blood vessels from the periosteum with Haversian canals.

How do Volkmann's canals generally run compared with Haversian canals?

They usually run at angles to the Haversian canals.

What do perforating canals provide for osteons?

Energy and nourishing elements.

What are the two methods of bone formation?

Endochondral bone formation and intramembranous bone formation.

What is endochondral bone formation?

Bone grows into and replaces a cartilage model.

What is intramembranous bone formation?

Bone develops from fibrous tissue membranes.

Which method produces most bones in the body?

Endochondral bone formation.

What happens during endochondral bone formation?

The body creates a cartilage template that is gradually replaced by bone.

Where does development of a long bone begin?

In the diaphysis, or shaft, of the cartilage model.

What is the primary growth center?

The area in the diaphysis where long-bone development begins.

Where are the secondary growth centers?

In the epiphyses, or ends, of the bone.

What are epiphyseal plates?

Plates of cartilage between the diaphysis and epiphysis that allow long bones to lengthen as the animal grows.

Where does intramembranous bone formation occur?

In certain bones of the skull.

What bones are produced by intramembranous bone formation?

The flat bones of the cranium surrounding the brain.

What does intramembranous bone formation develop from?

Primitive connective tissue containing collagen fibrils.

What fills the spaces inside bones?

Bone marrow.

What are the two types of bone marrow?

Red bone marrow and yellow bone marrow.

What is red bone marrow?

Hematopoietic tissue that forms red blood cells.

What does hematopoietic mean?

Capable of forming blood cells.

How much red marrow is present in young animals?

It makes up the majority of the marrow.

What happens to red marrow as animals age?

There is less of it and it becomes restricted to specific sites.

Where is red marrow found in older animals?

Ends of some long bones, interiors of the pelvic bones, and the sternum.

What is yellow bone marrow mainly made of?

Adipose tissue.

What type of marrow is most common in adults?

Yellow bone marrow.

Does yellow marrow normally produce red blood cells?

No.

Can yellow marrow become red marrow?

Yes, it can revert to red marrow if the body needs extra red blood cells.

What are the two major divisions of the skeleton?

Axial skeleton and appendicular skeleton.

What makes up the axial skeleton?

The bones of the head and trunk.

What makes up the appendicular skeleton?

The bones of the limbs.

What is the visceral skeleton?

A category of bones that form within soft organs or viscera.

What structures make up the axial skeleton?

Skull, hyoid bone, spinal column, ribs, and sternum.

Where are axial skeleton bones located?

On or near the median plane of the body.

How many bones does the skull consist of according to the lecture?

Approximately 37–38 bones.

How are most skull bones connected?

By immovable fibrous joints called sutures.

What is the only movable joint connected to the skull?

The mandible.

What is the occipital bone?

The bone forming the base of the skull.

What important opening is in the occipital bone?

The foramen magnum.

What passes through the foramen magnum?

The spinal cord.

What vertebra does the occipital bone articulate with?

The first cervical vertebra.

Why are injuries to the occipital bone rare?

It is surrounded by muscles, tendons, and ligaments.

What do the parietal bones form?

The dorsal and lateral walls of the skull.