Anatomy & Physiology I: Chapter 6

Skeletal tissues

What are the three types of cartilage?

Hyaline cartilage, elastic cartilage, and fibrocartilage.

What is the skeletal system?

It consists of bone & cartilage

What are the functions of the skeletal system?

It supports the body, protects organs, mineral & growth factor storage, hemtopoises, triglyceride storage, & osteocalcin production

What is skeletal cartilage?

They are structures of the skeleton that are sculpted to the body & consist of 3 types of cartilage tissues.

What are the major cells of cartilage?

Chondrocytes

Where are chondrocytes located?

They are encased in lacunae within the cartilage tissue.

Is cartilage vascular and innervated?

It is avascular and non innervated

Where is hyaline cartilage found in the body?

In the nose tip, larynx, joints, & ribs

Where is elastic cartilage located?

External ear & epiglottis

Where is fibrocartilage found?

Menisci of the knee & vertebral discs

What are seven important functions of bone?

Support, protection, movement, mineral storage, blood cell production, energy storage, and hormone production.

What are the major regions of the skeleton?

Axial skeleton and appendicular skeleton

What is the axial skeleton?

Consists of the skull, vertebral column, & thoracic cage.

What is the appendicular skeleton?

Consists of appendages (arms & legs)

What are the four classes of bone?

Long bones, short bones, flat bones, & irregular bones

What is a long bone?

A bone that is longer than it is wide

What is an example of a long bone?

The femur

What is a short bone?

A cube shaped bone

What are examples of short bones?

Wrists and ankles

What is a sesamoid bone?

It is a type of short bone that form within the tendons

What is an example of a sesamoid bone?

The patella

What is a flat bone?

A bone that is thin, flat, & slightly curved

What are examples of a flat bone?

The sternum, scapulae, ribs, and most cranial bones.

What is an irregular bone?

A bone that has a complicated or irregular shape

What are examples of an irregular bone?

The vertebrae and hip bones

What are the two sections of a long bone?

The diaphysis and epiphyses.

What is the diaphysis?

The tubular shaft that forms the long axis of a bone.

What is the diaphysis made of?

Compact bone on the outside and surrounds the medullary cavity.

What are the epiphysis?

The ends of long bones.

What are the epiphyses made of?

Compact bone on the outside and spongy bone inside. Hyaline cartilage lines the joint surfaces.

What is red marrow?

The site of hematopoiesis

What is hematopoiesis?

The production of blood cells & platelets

Where is red marrow found in infants?

It is found in the medullary & trabecular cavities of all spongy bones

Where is red marrow found in adults?

It is found in the trabecular cavities in the head of the femurs & humerus, flat bones of the skull, sternum, ribs, clavicles, scapulae, vertebrae, & hip bones

What is yellow marrow?

It consists of adipocytes (fat cells) & serves as energy reserve.

Where is yellow marrow found?

It is found in the medullary cavities

What occurs to yellow & red marrow during anemia?

Yellow marrow can convert into red marrow

What is the periosteum?

It is double layered and lines the outside of compact bone

What is the fibrous layer of periosteum?

The outer layer is made of irregular connective tissue. The perforating fibers secure the membrane to the bone.

What is the osteogenic layer of periosteum?

The inner layer, which contains osteoprogenitor stem cells.

What is the endosteum?

It is a single-layered structure that lines the inside of compact bone. It covers the trabeculae, nutrient foramen, & medullary cavity. It contains osteoprogenitor stem cells.

What are osteoprogenitor stem cells?

Mitotically active stem cells in the periosteum & endosteum.

What occurs when osteoprogenitor cells are stimulated?

They differentiate into osteoblasts or bone-lining cells. Some remain as osteoprogenitor cells.

What are the three main categories of bone markings?

Projections, depressions, and openings.

What are projections?

An outward bulge of the bone surface which serves as the attachment site for muscles, ligaments, & tendons

What is a depression?

A bowl or groove-like cut-out of a bone surface. They serve as passageways for vessels & nerves. They play roles in joints.

What is an opening?

A hole or canal into bone. They serve as passageways for vessels & nerves.

What is an osteoblast?

It is a bone-forming, mitotically active cell. It secretes osteoid

What is osteoid?

90% of it is made of collagen & calcium binding proteins

What is an osteocyte?

Mature bone cells in the lacunae. They are not mitotically active. They maintain the bone matrix.

What are bone-lining cells?

They are flat cells on a bone surface that maintain the matrix

What are periosteal cells?

They are a type of bone-lining cells that line the external bone surface.

What are endosteal cells?

They are a type of bone-lining cells that line the internal bone surface

What is compact bone?

The dense outer layer on every bone. It appears smooth & solid.

What is spongey bone?

A honey comb of sm

What makes up compact bone?

Osteons, the central canal, perforating canals, lacunae, & canaliculi.

What is an osteon?

The structural unit of compact bone

What makes up an osteon?

It consists of rings of lamellae.

What are lamellae?

They contain collagen fibers that go in different directions to withstand stress & twisting. Bone salts are between the collagen fibers.

What are concentric lamellae?

Ring layers of osteon

What are interstitial lamellae?

They are not a part of an osteon. Some fill gaps between forming osteons & others are remnants of bone remodeling.

What are circumficial lamellae?

They are intermediate to periosteum & endosteum. They extend around the entire diaphysis & are twist-resistant.

What is the central canal?

It runs through the core of an osteon. It contains nerves & blood vessels.

What is a perforating canal?

They connect blood vessels & nerves of the periosteum, medullary cavities & central canal.

What are lacunae?

They are small cavities that contain osteocytes

What are canaliculi?

They are hair-like canals that connect lacunae to each other & to the central canal

What are trabeculae?

They are strong needle-like projections. They contain no osteons. Irregularly arranged lamellae & osteons are connected by canaliculi. 

What supplies nutrient to trabeculae?

Capillares in the endosteum.

What are the organic components of bone?

Osteogenic cells, osteoblasts, osteocytes, osteoclasts, bone-lining cells, & Extracellular matrix

What is the most abundant inorganic component of bone?

Hydroxyapatite

What are Hydroxyapatites?

They consist of tiny calcium phosphate crystals in & around collagen fibers. They make up 65% of bone by mass. They allow for hardness & compression resistance

What is the purpose of Hydroxyapatites?

They allow for hardness & compression resistance

What is ossification?

The process of bone tissue formation

When does ossification occur?

It begins in month 2 of development and ranges from postnatally to early adult hood.

What is intramembranous ossification?

A process where bone tissue forms from a fibrous membrane

What type of bones form from intramembranous ossification?

Flat bones like the clavicle & cranial bones

What is endochondral ossification?

A process where bones develop by replacing hyaline cartilage resulting in encochondral bones

What type of bones form from endochondral ossification?

Long bones like the humerus & femur.

What is longitudinal growth?

It occurs postnatally and is when long bones grow longer & hyaline cartilage turns to bone.

Where does longitudinal growth occur?

It occurs from the epiphyseal plate. When growth stops, the plate becomes the epiphyseal line.

What is appositional growth?

It occurs postnatally and is the process of bone thickening. It occurs done bone remodeling.

Is bone growth still possible after the epiphyseal plate closes?

Only appositional growth is possible

What regulates bone growth?

It is regulated by hormones

What do growth hormones do?

They stimulate epiphyseal plate activity in infancy & childhood.

What does the thyroid hormone do?

It modualtes the activity of growth hormone & ensures proper proportions.

What influence do testosterone & estrogen have on bones?

At puberty, they promote growth spurts & end growth by inducing epiphyseal plate closure.

What is bone remodeling?

The process of preventing brittle bones by replacing bone.

What triggers bone remodeling?

Mechanical stresses, changes in calcium or phosphate & hormones.

How often is spongy bone replaced?

It is completely replaced every 3-4 years

How often is compact bone replaced?

It is completely replaced every 10 years

What are remodeling units?

Packets of adjacent osteoblasts & osteoclasts

What is the role of osteoblasts in bone remodeling?

They are responsible for bone formation. They deposit new bone matrix.

What triggers osteoblasts?

Increased mechanical stress & an increase in calcium or phosphate

What is the role of osteoclasts in bone remodeling?

They resorb bone to release calcium. They dig depressions or grooves into bone. The matrix is digested with lysosomal enzymes & acids. 

What triggers osteoclasts?

A decrease in mechanical stress, a decrease in calcium, & parathyroid hormone.

What are non displaced fracture?

The ends retain a normal position

What is a displaced fracture?

The ends are out of normal alignment

What is a complete fracture?

When a bone is broken all the way through

What is a compound (open) fracture?

When the skin is penetrated

What is a simple (closed) fracture?

When the skin isn’t penetrated