Ch 6: The Skeletal System

BIOL 2301 - Margarita Bracamonte _ HCCS

What are the functions of the skeletal system?

Supports the body by attaching to the skeletal muscles, stores/releases minerals like calcium and phosphorus, makes/releases blood cells and platelets, and protects internal organs.

How many bones does an adult skeleton have?

206.

How many bones does a newborn baby skeleton have?

Around 300.

Why do adults have less bones than babies?

As a person gets older some bones fuse together.

What are the five categories of bones?

1. Long bones

2. Flat bones

3. Sesame void bones

4. Short bones

5. Irregular bones

What is the shape of long bones like?

Involves two expanded ends - distal and proximal - with a shaft in between them.

What is the function of a long bone?

They are used as levers.

What are examples of long bone?

The femur, humorous, phalanges, and the tibia.

Are all long bones long?

No, long bone just refers to their shape not necessarily their size.

What is the shape of short bones like?

Nearly equal in length and width - small and boxy.

What is the function of a short bone?

Provide stability and support with limited movement.

What are examples of short bone?

Carpools (wrist bones) and tarsals (ankle bones).

What is the shape of flat bones like?

Thin and curved.

What is the function of a flat bone?

Points of attachment for skeletal muscles and protects organs.

What are examples of flat bone?

Sternum, ribs, and cranial bones.

What is the shape of irregular bones like?

Have complex shapes that don't fit into other categories.

What is the function of a irregular bone?

Protect organs.

What are examples of irregular bone?

The Coxa (hip bone), vertebrae, and the sphenoid.

What is the shape of sesamoid bones like?

Small and round similar to a sesame seed.

What is the function of a sesamoid bone?

Protects tendons from comprehensive forces.

What are examples of sesamoid bone?

The patella (knee bone).

What is another name for an expanded end?

An epiphysis.

What is the function of epiphyses?

Serve as articulations/connections between bones.

What is the shaft of a long bone between the epiphysis called?

The diaphyses.

What does a diaphyses contain?

The medullary and marrow cavities.

What is inside the medullary cavity?

Yellow bone marrow.

What are the walls of the diaphysis made from?

Compact bone.

What is the function of the diaphysis in the long bone?

Providing weight support.

What is bone tissue made out of?

Bone connective tissue.

What is the bone extracellular matrix made up of?

Mineral salts and proteins.

What are the mineral salts in the extracellular matrix of bone connective tissue made above?

Crystals of hydroxyapatite that form from calcium phosphate + calcium carbonate.

What are the matrix proteins of bone connective tissue?

collagen fibers.

How much of the bone matrix is collagen fibers?

About 1/3.

What do hydroxyapatite crystals give the bone?

It's hardness and it's strength.

What do collagen fibers give the bone?

Its flexibility to prevent it from becoming brittle and break easily.

What are the four types of cells found within bone tissue?

1. Osteogenic cells

2. Osteoblast cells

3. Osteocyte cells

4. Osteoclast cells.

What are osteogenic cells in terms of cellularity?

Stem cells.

What are osteogenic cells for?

They divide by mitosis turning into osteoblasts.

Where are osteogenic cells found?

In the periosteum and endiosteum of bones.

What does an osteogenic cells turn into? How?

Osteoblast cells through mitosis.

What is a characteristic of osteoblast cells?

They are immature cells.

What are osteoblast cells for?

New bone and bone matrix formation through the releasing of collagen fibers and calcium salts.

Where are osteoblast cells found?

In the periosteum of bones.

What does an osteoblast cells turn into? How?

Into osteocytes once it is surrounded by calcified bone matrix.

What are osteocyte cells physically like?

Are mature, live in structures called lacunae and are the most common type of bone tissue cell.

What are osteocyte cells for?

Maintaining the bone matrix and helping repair damaged bone.

Where are osteocyte cells found?

In bone tissue.

What do osteoclasts originate from?

From monocytes (white blood cells).

What are osteoclasts cells physically like?

Giant and multinucleated cells.

What are osteoclasts cells for?

Dissolving bone matrix and releasing of stored minerals to the blood.

Where are osteoclasts cells found?

In the endosteum.

What are the two types of bone tissue that bones are made out of?

Spongy and compact bone.

What is another name for compact bone?

Cortical bone.

What is compact bone made out of?

Compacted bone tissue.

What does compact bone provide?

Protection and support to the body.

What does compact bone resist?

Stress produced by weight and movement.

What structural unit is compact bone composed of?

Units called osteons.

What is another name for osteons in compact bone?

Haversian system.

What is at the center of each osteon?

A central canal.

What does the central canal of an osteon contain?

Blood vessels that carry blood to and from osteons and nerves.

What branches from the central canals?

Perforating canals.

What do perforating canals contain?

Blood vessels that carry blood to deeper parts of the bone and nerves.

What is the periosteum in bones?

The superficial layer of the bone.

What does the periosteum contain in bones?

Osteoblasts.

What is the function of the periosteum?

Provides strong attachment for skeletal muscles.

What is the endosteum?

A connective tissue membrane lining the medullary cavity of long bones and trabeculae of spongy bone.

What is another name for spongy bone?

Cancellous bone.

What is spongy bone composed of?

Less dense bone tissue.

What does spongy bone contain?

Bundles of fibers called trabeculae.

What are the spaces between spongy bone trabeculae filled with?

Red bone marrow.

What is red bone marrow?

A connective tissue that forms blood cells and platelets.

What is the benefit of bones being filled with spongy bone rather than compact?

Provide strength without adding too much weight to the bone.

What is osteoporosis?

A disease that causes severe bone loss in both spongy and compact bones.

What does osteoporosis do to the bones?

Severely impacts their strength.

What percentage of men and women over the age of 45 does osteoporosis occur in?

29% of women and 18% of men.

What causes osteoporosis?

Sex hormones.

Why does the condition of osteoporosis get worse in postmenopausal women?

Due to low estrogen.

What is a secondary effect of osteoporosis?

Many types of cancers.

What is the process of bone formation called?

Ossification.

When do bones form in a fetus?

About six weeks after egg fertilization.

What are existing bone elements made up of in embryos?

Hyaline cartilage.

What are the two major forms of ossification processes?

Intramembranous ossification and endochondrial ossification.

What is the least common type of ossification?

Intramembranous ossification.

What bones are typically formed by intramemberness ossification?

Flat bones in the skull, facial bones, the clavicle, and mandible.

What do bones formed by intramumburnous ossification come from?

Typically fibrous connective tissues similar to the dermis of the skin.

Do bones get remodeled throughout their whole life?

Yes.

What two directions do bones grow and shrink in?

Lengthwise and thickness wise.

What is another name for lengthwise growth in bones?

Interstital growth.

What is the epiphyseall plate in bones? What kind of bones is it present in?

A cartilaginous zone where long bones grow in length.

Where is the epiphyseal plate in long bones located?

At the distal and proximal ends of the bone between the epiphysis and the diaphysis.

What is the epiphyseal plate made out of?

Hyaline cartilage.

When does the epiphyseal plate close? Why? What does this mean for the human?

In the late teens and early 20s, due to calcification meaning that the human has reached its final height.

What is the site of the original epiphyseal plate marked with? What is it called?

A line of slightly spongy bone called the epiphyseal line.

What is gigantism?

Overproduction of the growth hormone before puberty which causes the epiphyseal plate to continuously deposit bone matrix causing the person to become over eight feet tall.

What causes gigantism?

A benign tumor of the pituitary gland that makes it significantly bigger than normal.

What is the name for bone growth in thickness?

Appositional growth.

When does appositional growth end?

Never, it is constantly remodeling bones.

What are the two bone cells involved in appositional growth?

Osteoblasts and osteocytes.

How are osteoblasts and osteocytes connected through appositional growth?

They work together through similar speeds that cause bone to be destroyed and renewed at the same time.

Do osteoblasts and osteocytes always work together?

No they sometimes work at different speeds.