A&P Chapter 7 Skeletal System: Bone Formation, Repair and Osteoporosis Flashcards Preview

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Flashcards in A&P Chapter 7 Skeletal System: Bone Formation, Repair and Osteoporosis Deck (104):

What is Osseous tissue?

Hardened connective tissue consisting of cells, mineral deposits and collagen.


What is bone (as an organ)?

The skeletal structure consisting of osseous tissue, a variety of different types of bone cells, blood vessels, nerve, cartilage, fibrous connective tissue and adipose tissue.


What are the functions of the Skeletal system?

1. Support; bones support the body's weight.
2. Protection; bones protect the brain and other internal organs. Bone also produces WBC's important for immune response.
3. Movement; Bones provide attachment points for muscles which allow for movement of the body, breathing, eye movement ect...
4. Electrolyte balance; Bones act as a storage reservoir for Calcium and phosphate ions.
5. Acid-Base balance; Alkaline salts (basic) released by bones buffer against changes in blood pH.
6. Blood formation; bone marrow located in the center of many bones is the site of blood cell formation.


What is the Periosteum?

Outer covering of bones consisting of fibrous connective tissue and a layer of bone forming cells.

Layer of OSTEOGENIC stem cells between the Periosteum and the compact bone deep to it.

Provides for the attachment of muscles, connective tissues of tendons fuse with the periosteum.


What is Compact bone?

Dense layer of osseous tissue that makes up the outer portion of a bone creating a hollow center.


What is the Marrow Cavity?

Inner compartment of a bone that contains bone marrow.


What is Bone marrow?

Soft tissue composed of adipose tissue and or HEMATOPOIETIC tissue that is responsible for blood cell formation.


What is Yellow Marrow? Where is it found?

Yellow marrow is adipose tissue left behind in most long bones of ADULTS.


What is Red Marrow? Where is it found?

It is HEMATOPOIETIC tissue that is responsible for blood cell formation. It is found in the long bones of children and in the axial skeleton of adults as well as the heads of the Femur and Humerous bones.


What is the Endosteum?

The thin layer of reticular connective tissue that lines the marrow cavity, it also contains osteogenic cells.


What is spongy bone?

Lighter, less dense bone found at the ends of long bones or middle of flat bones. Spongy bone is always covered by compact bone and periosteum.

Spongy bone is affected more than compact bone by Osteoperosis.


What is the Diaphysis?

The main shaft of a bone usually where muscles attach.


What is the Epiphysis?

The end of a bone that articulates with other bones to form a joint.


What is the epiphyseal plate/line?

A layer of hyaline cartilage that separates the epiphysis from the diaphysis. In children and adolescents this is the zone of dividing cells that allows bones to grow longer, the GROWTH PLATE.

In adults the hyaline cartilage transitions into bone creating the epiphyseal LINE.


What are Nutrient foramina?

Perforating holes that allow blood vessels to enter the bone and transport nutrients and waste.


Bone or osseous tissue is what kind of tissue class? And as such it has what BASIC components?

It is Connective tissue, as such it has cells, fibers and ground substance.


What are the basic bone cells?

Osteogenic cells, Osteoblasts, Osteocytes, and Osteoclasts.


What are Osteogenic cells?

Stem cells; Undifferentiated cells that will mature and become osteoblasts.


What are Osteoblasts?

Bone forming cells which actually sythesize the hard bone matrix.


What are Osteocytes?

Mature osteoblasts that live in Lacunae.


What are Osteoclasts?

Large muti-nucleated cells whose job is to dissolve bone.


What does the Ruffled border on an Osteoclast do?

Secretes a protease and hydrochloric acid to dissolve osseous tissue.


What is the non-cellular, ground substance of osseous tissue called?

Bone Matrix


What is bone matrix comprised of?

Organic and Inorganic protein matter.


What is the Organic protein matter of bone matrix? How much of it forms bone matrix in a healthy person?

It is primarily collagen, proteoglycans and glycoproteins. It comprises 1/3 of bone matrix.

The organic protein matter gives bones their flexability.


What is the Inorganic matter of bone matrix? How much of it forms bone matrix in a healthy person?

Mostly, Hydroxyapatite and Calcium Carbinate, with a smaller amount of other minerals and ions. It comprises 2/3 of bone matrix.

It is responsible for the bone strength and rigidity.


Bone matrix is said to be a COMPOSITE, what does this mean?

That it is a combination of two or more structural components, the Organic matter and the Inorganic matter.


What gives Bone matrix its strength and rigidity?

The Inorganic matter approx. 2/3 of total bone matrix.


What gives bone matrix its flexability?

Organic protein matter, approx. 1/3 of total bone matrix.


Describe Compact Bone

Dense osseous tissue that encloses marrow cavity and surrounds spongy bone.


The matrix of compact bone is organized into units called?



Describe an Osteon

A central canal (Haversian canal) surrounded by concentric rings of bone matrix called Lamellae. Lacune with Osteocytes are encased in the bone matrix with Canaliculi connecting the lacunae.


What is a Central/Haversian Canal?

A long canal at the center of an Osteon that contains blood vessels and nerves.


What are Canaliculi?

Tiny ducts that connect lacunae to one another and allow osteocytes to communicate.


What are Volkman's Canals?

Ducts carrying blood vessels and nerves from nutrient foramina to central canals or from one central canal to another.


What are Circumferential Lamellae?

The layers of osseous tissue that encases all the osteons in a bone into one bone.


How do Osteocytes communicate with each other?

Tiny canaliculi allow for communication via gap junctions.


Describe Spongy Bone

Consists of a meshwork of thin rods and plates (called TRABECULAE) of osseous tissue giving the bone a sponge like appearance. .

The TRABECULAE are organized in a specific manner so they can resist stress.


Where is Red Marrow found?

Pelvis, skull, ribs and in the head of the femur and humerous. Basically the axial skeleton in Adults.

As children and infants, red marrow is in almost every bone.


Where is blood marrow for transplant harvested from?

The Ilium


What is Yellow marrow?

Primarily adipose tissue


What is HEMATOPOIETIC tissue?

The tissue that is found in red bone marrow responsible for blood formation.


What are the two ways that bones develop?




Flat bones, the skull and clavicle



Most bones form this way, bone development begins around the 6th week of development and ends in the average person's 20's.

Bones start as a piece of hyaline cartilage surrounded by a circular collar of bone and a centrally located PRIMARY OSSIFICATION CENTER where the lacunae of the cartilage grow larger and become calcified.


What happens when blood vessels enter the Primary Ossification Center?

Osteoblasts work to replace hyaline cartilage with osseous tissue.

Osteoclasts then follow behind and dissolve some of the new bone away to create a hollow marrow cavity in the center of the bone.


What is the Metaphysis?

The region at the ends of forming bone where cartilage is converted to osseous tissue.


What happens when Blood vessels invade the Epiphyses of the bone?

They help create a Secondary Ossification Center which will hollow out creating a Secondary Marrow Cavity which will eventually be filled with spongy bone.


After the Secondary Marrow Cavity has been formed where are the only locations of Hyaline Cartilage?

The Epiphyseal plate and the Outer surface of the ends of the bones, known as Articular Cartilage


Where is Articular Cartilage found?

The outer surface of the ends of the bones.


When does the Epiphyseal plate change from Cartilage to Bone? What is it called after it turns to bone?

In your early 20's, after it turns to bone it is called the Epiphyseal LINE


Describe in detail what the Epiphyseal plate looks like.

It is a band of hyaline cartilage sandwiched between two transitional zones called Metaphyses,


Without the ___________ ___________ we would be very short.

Epiphyseal plate, A.K.A. the Growth Plate


How do bones grow longer?

Growth occurs at the Epiphyseal plate, the amount of hyaline cartilage increases when it does some of the cartilage at the upper and lower edges of the Epiphyseal plate becomes ossified.

This process od cartilage expansion in the epiphyseal plate and ossification at the metaphyses repeats over and over thus extending the length of the bone.



The widening and thickening of bone.


Explain how Appositional growth occurs

A thin layer of osteoblasts reside between the periosteum and the surface of the bone. As those osteoblasts lay down more and more bone on the surface the bone becomes thicker and wider.

Osteoclasts on the inside of the marrow cavity dissolve away some of the bone allowing the marrow cavity to grow and become larger.

This process prevents bones from becoming overly dense and heavy due to growth.


Explain Bone Remodeling

The result of the combined actions of osteoblasts and osteoclasts synthesizing and dissolving bone matrix.


What is Bone Deposition?

When osteoblasts synthesize bone matrix creating more osseous tissue.


What is Bone Resorption?

When Osteoclasts dissolve bone matrix removing osseous tissue.


What important roles does Bone Remodeling play?

1. Repair of Microfractures
2. Development of Bone Features (tubercles, condyles, facets, etc...)
3. Mineral release/absorption from the bloodstream.
4. Bone reshaping in response to mechanical stress, Wolff's Law of Bone.


What is Wolff's Law of Bone

Bone architecture is determined by mechanical stresses placed on it.


Explain Stress Lines

The Trabeculae of spongy bone will increase in density and orient themselves to accommodate increased mechanical stress forming Stress Lines.


What is calcium critical for? What is low blood calcium called? What about high blood calcium?

Calcium is critical for the contraction of muscle cells and transmission of nerve signals.

Low Blood Calcium is called Hypocalcemia, it causes muscle cells and nerves to become easily excitable leading to spasms, tremors and tetany.

High Blood Calcium is called Hypercalcemia and it makes muscle cells and nerves unresponsive. Can lead to coma, cardiac arrest or death.


What is Phosphate critical for?

It is a critical component of many biological macromolecules like DNA, RNA, proteins, phospholipids and ATP.


What is the normal range for Blood Ca2+?



What is the normal range for Blood Phosphate?

3.5/4.0 mg/dl


What does Mineral deposition do to maintain Blood Ca2+/PO43-? What cell carries out this task?

It helps lower blood Ca2+ and Phosphates by removing them from the blood stream and depositing them into osseous tissue.

Osteoblasts carry out mineral deposition, they lay down a layer of collagen fibers which is initially coated with hydroxyapatite which attracts more calcium and phosphate from the blood thus DECREASING the amount of Calcium/Phosphate in the bloodstream.


What is Mineral Deposition?

The process by which minerals are removed from the bloodstream and deposited into osseous tissue.


What is Mineral Resorption?

The process by which bone is dissolved by Osteoclasts thereby releasing calcium/phosphate into the blood.


What does Mineral Resorption do to maintain Blood Ca2+/PO43-? What cell carries out this task?

It helps raise the levels of Calcium and Phosphate in the blood by dissolving bone matrix thus RELEASING the calcium and phosphate.

Osteoclasts carry out this task by secreting Hydrochloric acid (HCl) which dissolves bone minerals and enzymes which degrade collagen. This INCREASES the levels of Calcium and Phosphate in the bloodstream.


All tissues have collagen, minerals and phosphates in them, what prevents them from turning into bone?

Most tissues contain inhibitors that prevent mineral deposition and ossification.



Hardening of the arteries, this is an example of abnormal ossification.


What are the three hormones that help regulate Ca2+/phosphate levels in the bloodstream?

Calcitriol, Calcitonin, and Parathyroid hormone.


Describe Calcitriol

It is a form of Vitamin D, Exposure of the skin to UV light contributes to synthesis in the body, it also comes from Vitamin D added to milk.

Overall, calcitriol INCREASES blood Ca2+ levels by:

Increased intestinal absorption of Calcium
Triggers the differentiation of stem cells into Osteoclasts which then dissolve more bone away (Mineral Resorption)
Weakly inhibits loss of Ca2+ through the Kidneys


Describe Parathyroid Hormone (PTH)

It is released by the Parathyroid gland.

Overall it INCREASES Ca2+ levels in the blood stream by:

Stimulating the differentiation of Osteoclasts contributing to Mineral Resorption
Decreases the loss of Ca2+ by kidneys so more is retained in the blood stream.
Inhibits Osteoblast formation (TRIPLE WHAMMY), less bone formation, less mineral Deposition.


Describe Calcitonin

A hormone secreted by the thyroid gland

Overall is DECREASES the Ca2+ levels in the bloodstream when levels get too high by:

Inhibiting osteoclast activity which inhibits Mineral Resorption
Stimulates Osteoblasts which increases bone formation and Mineral deposition.

This is more important in children than Adults.


Which Calcium/Phosphate hormone is more important in children than adults?



Which Calcium/Phosphate regulatory hormones increase Ca2+ levels? Which decreases it?

Calcitriol and Parathyroid Hormone INCREASE the levels in the bloodstream

Calcitonin DECREASES the levels in the blood stream.


What are the two CAUSES of fractures?

Stress Fracture, Pathologic Fractures


Describe a Stress Fracture

Cause by the abnormal trauma to a bone from an external force.


Describe a Pathological fracture

Caused due to the weakening of the bone due to pathology or disease.


What are the TYPES of fractures?

Simple fracture, Compound fracture, Complete and Incomplete


Describe a Simple Fracture

The bone is broken but does NOT break through the surface of the skin.


Describe a Compound Fracture

The Bone is broken and pierces through the overlying skin, two tissues are damaged the bone and the skin.


Describe a Complete Fracture

When the bone is broken into TWO or MORE pieces


Describe an Incomplete Fracture

The fracture only extends part way through the bone, the bone pieces remain joined.


How many phases does Fracture repair have? How long does it take?

4 Phases, 8-12 Weeks with Complex fractures taking longer to heal.


What is the first phase of Fracture Repair?

Hematoma formation and Granulation

When the bone breaks blood vessels are severed leading to bleeding. A Bloodclot is formed around the site of the fracture.

Fibroblasts, Osteogenic cells and blood vessels invade the area creating a soft mass of tissue called GRANULATION TISSUE


What is Granulation Tissue?

The soft mass formed after a hematoma stops the bleeding from a break in a bone.

Fibroblasts, osteogenic cells and blood vessels invade the area creating a soft mass of tissue called the Granulation tissue.


What is the Second phase of Fracture repair?

Soft Callus Formation

Fibroblasts deposit collagen that creates a fibrous patch around the fracture known as a SOFT CALLUS.


What is the Third Phase of Fracture Repair?

Hard Callous formation.

Lasts approx. 2 months.

Osteoblasts lay down a collar of new bone surrounding the fracture called a hard callus. This is the bodies version of a cast that keeps the pieces of bone properly aligned during healing.

The fracture is still fragile and can be broken easily.


That is the Fourth phase of Fracture Repair?


This is a slow process by which the broken pieces of bone are remodeled and gaps are filled.

Osteoclasts remove small fragments and smooth jagged edges.

Osteoblasts enter and lay down a layer of SPONGY BONE first to close any gaps which prevents a bone from shortening after a fracture.

The spongy bone transitions to compact bone and the fracture site is nearly undetectable.


What are the treatments of Fractures?

Closed Reduction, Open Reduction and Traction


Describe Closed Reduction

This is the treatment for a fracture WITHOUT surgery. Common for incomplete fractures, a cast is left in place through hard callus phase of healing.


Describe Open Reduction

This is the treatment of fractures that uses surgery to expose the bone and implant screws, pins, and plates to stabilize and align bones.


Describe Traction

This is the use of mechanical force to align bones during the early stages of healing. Commonly used in femur fractures.


Describe Osteoporosis

A disease in which bones become LESS dense, very brittle and susceptible to fracture (pathological fracture)

It literally means Porous bones.

Bone Mineral Density is decreased due to lack of new bone formation.

Spongy bone is affected most.


Where are the most common fracture sites with Osteoporosis?

Distal radius (Colles fracture), vertebrae, and neck of femur.


How many fractures caused by Osteoporosis lead to death in the elderly? What causes death?

1-5. Infection, blood clots or immobilization.


Compression of vertebrae can reduce overall height by how much?




Known as Widow's Hump. It is a curvature of the spine cause by a compression of vertebrae.


What are the risk factors for Osteoporosis?

1. Females of Asian or Caucasian ethnicity.
2. Low Estrogen levels cause by onset of Menopause or Extreme weight loss or lack of body fat stops ovulation known as Amenorreha
3. Poor Diet; Low intake of Calcium and Vit. D
4. Smoking; Inhibits Osteoblast activity
5. Sedentary lifestyle; Use it or Lose it. No mechanical stress to stimulate osteoblasts.
6. Glucocorticoids; a steroid used to treat inflammatory diseases like arthritis and asthma. Glucocorticoids inhibit Osteoblast activity AND promote Osteoclast maturation.


What is Amenorreha?

The absence of menstruation.


What is Cushing's Syndrome

When the body produces abnormally high levels of Glucocorticoids.