A & P: Chapter 6-The Skeletal System (Bone Tissue)

Functions of Skeletal System (6)

1. Support
2. Protection
3. Movement
4. Mineral Storage and Homeostasis
5. Blood Cell Formation (Hemopoiesis)
6. Fat Storage

Skeletal System is Made of... (6)

1. Bone Tissue
2. Cartilage
3. Dense Connective Tissue
4. Adipose Tissue
5. Blood/Vascular connective tissue
6. Nervous Tissue

Support

Function of Skeletal System that forms the framework of the body.

Protection

Function of Skeletal System that encloses vital organs (heart, brain, lungs)

Movement

Function of Skeletal System that along with the muscles, helps move the body.

Mineral Storage and Homeostasis

Function of Skeletal System that stores calcium and phosphate.

Hemopoiesis

Function of Skeletal System that is Blood Cell Formation; houses red bone marrow that has stem cells to form RBC, WBC, and platelets

Fat Storage

Function of Skeletal System in which bones store fat as yellow bone marrow.

Short Bone

Bone Shape that is small, like cubes; Bones of the wrist and ankle.

Flat Bone

Bone Shape like plates; bones of the cranium, hip, ribs

Long Bone

Bone Shape that is long and thin; bones of the arms and legs, palms, soles, fingers, toes

Irregular Bone

Bone Shape that is irregular, complex shape; Vertebrae and facial bones and pelvis

Sesamoid Bone

Bone Shape that has bones wrapped inside a tendon; patella

Sutural Bone

Bone Shape; bones found between cranial bones; borders are like jigsaw puzzles; small as grain or quarter

Bone Markings

Surface Features that help in naming of the bone parts, provide information on muscle and ligament attachments, passage of blood vessels and nerves, and bone articulations; used by physicians to locate some of the internal structures

Foramen

A rounded passageway for blood vessels or nerves.

Process

A Bone Marking that is any projection or bump.

Fossa

A Bone Marking that is a shallow depression.

Diaphysis

The shaft of a long bone; made of mostly compact bone tissue

Epiphysis

The two ends of a long bone; made mostly of spongy bone tissue; spaces filled with red bone marrow.

Metaphysis

The area between diaphysis and epiphysis; Has the cartilaginous epiphyseal plate before puberty

Cortex

A thin covering of the spongy bone.

Compact Bone

A solid, sturdy protective layer that surrounds the central space or medullary cavity.

Spongy Bone

Consist of an open network of struts and plates that resemble lattice work with a thin covering.

Medullary Cavity

Cavity in the Diaphysis that is filled with yellow bone marrow; means marrow cavity

Periosteum

Dense connective tissue membrane covering the outer surface of the long bone, for muscle attachment; help with the growth and repair of the bone.

Endosteum

Dense connective tissue lining the medullary cavity; it is an incomplete cellular layer containing osteoblasts, osteoprogenitor cells and osteoclasts; to help with the growth and repair of the bone.

Bone Tissue

Connective Tissue that is composed of dispersed cells with solid extracellular matrix.

4 Types of Bone Cells

1. Osteoprogenitor Cells
2. Osteoblasts
3. Osteocytes
4. Osteoclasts

Osteoprogenitor Cells

Mysenchymal cells that are squamous stem cells; Dividing stem cells that differentiate into osteoblasts; located in the endosteum, deeper portions of periosteum; their division produce osteoblasts

Osteoblasts

immature bone cells that secrete extracellular matrix (collagen fibers and calcium salts); produce new bone matrix through ossification

Osteocytes

Mature bone cells formed by osteoblasts trapped inside solid extracellular matrix; function to maintain bone tissue by maintaining the protein and mineral content of the surrounding matrix and help repair damaged bone; develop from osteoblasts that have become completely surrounded by bone matrix.

Osteoclasts

Cells that remove and recycle bone matrix; Modified white blood cells that fight infection; they break down bone tissue (bone resorption); they are mutinucleated cells that secrete acids and enzymes to dissolve bone marrow

Extracellular Bone Matrix

Collagen fibers for flexibility; Salts for strength; calcium phosphate and calcium carbonate.

Two Types of Bone Tissue

Compact and Spongy Bone Tissue

Compact Bone Tissue

80% of bone; Makes up most of the diaphysis of long bone; supports movement and weight of the body characterized by its dense arrangement.

Osteons

The basic functional unit of mature compact bone.

Central Canal

In the osteon, contains one or more blood vessels that carry blood to and from the osteon.

Concentric Lamellae

Surround the central canals by concentric rings of bony matrix.

Lacunae

Scattered between the lamellae are spaces that house the osteocytes.

Canaliculi

Narrow passageways that penetrate the lamellae, they radiate through the matrix and connecting lacunae with one another and with sources of nutrients, such as blood vessels in the central canal.

Spongy Bone

Bone Structure where Lamellae are not arranged in osteons; Matrix forms a meshwork of supporting bundles of fibers; no capillaries or venues in the matrix of spongy bone

Trabeculae

inside the spongy bone; made of concentric rings called lamellae; scattered between are lacunae with osteocytes; and the canaliculi connect lacunae to the surface; the spaces contain red bone marrow

Red Bone Marrow

involved in Hemopoiesis (blood cell formation); blood vessels and nerves

Yellow Bone Marrow

Spongy Bone can contain this marrow that is adipose tissue important as an energy reserve.

Ossification

Bone Formation; Begins in the fetus with mesenchymal tissue that will undergo transformation to form bones.

Intramembranous Ossifcation

Process for bone formation that involves deposition of osseous tissue within mesenchymal membranes; forms the flat bones of the skull; also called dermal ossification

Endochondral Ossification

Process for bone formation that involves the replacement of a hyaline cartilage "mold" with osseous tissue; forms most bones in the body.

Fontanels

When a newborn skull still contains areas where process is not complete--soft spots

Ossification Center Development

1st step in Intramembranous Ossifiction that involves the mesenchymal cells aggregate and differentiate into osteogenic cells. They then transform into osteoblast cells that produce bony matrix.

Calcification

2nd step in Intramembranous Ossification in which osteoblasts become completely surrounded by extracellular matrix, become osteocytes in lacunae, and canaliculi form. Classification of extracellular matrix occurs with the accumulation of calcium and mineral salts.

Trabeculae Formation

3rd step in Intramembranous Ossification in which extracellular matrix join up to form trabeculae of spongy bone; Spaces between trabeculae are penetrated by blood vessels and red bone marrow is estabilished.

Periosteum Development

4th step in Intramembranous Ossifiction in which the remaining mesenchymal cells at the periphery differentiate into the poriosteum. Compact bone tissue develops replacing the spongy bone tissue.

Cartilage Model Development

1st step in Endochondral Ossification; mesenchymal cells differentiate into chondroblast that lay down cartilage matrix forming a cartilage mold of the future bone; surrounding membrane becomes the perichondrium.

Cartilage Model Growth

2nd step in Endochondral ossification; interstitial gowth occurs--chondocytes divide and secrete cartilage matrix causing linear growth of the model; increased matrix at the periphery from chondrocytes deep to the perichondrium causes appositional growth (widening). Chondrocytes hyperophy and matrix begins to calcify; some chondrocytes die and leave behind large lacunae.

Primary ossification center development

3rd step in Endochondral ossification; nutrient artery penetrates perichondrium; osteogenic cells differentiate into osteoblast; begin to produce bondy matrix; perichondrium now a periosteum; primary ossification center forms as osteoblast deposit bony matix over calcified cartilage matrix forming spongy bone.

Medullary Cavity Formed

4th sep in Endochondral ossification; Osteoclast brought in by nutrient artery begin to hollow out spongy bone at the middle of the bone forming medullary cavity; formation of spongy bone continues towards the epiphyses; spongy bone will be replaced by compact bone.

Secondary Ossification Centers Development

5th step in Endochondral Ossification; branches of epiphyseal arteries penetrate into the epiphyseal areas of model and stimulate the formation of secondary ossification centers; Osteogenic cells differentiate into osteoblast laying down bony matrix; spongy bone formation proceeds outward the periphery; no formation of medullary cavity.

Articular Cartilage Formation

6th step in Endochondral ossification; at the surface of the epiphyses, hyaline cartilage will remain as articular for the bone; areas between the epiphyses and the diaphysis of bone will remain as epiphyseal plates containinig hyaline cartilage that will allow the bone to grow in length.

Interstitial Growth

For increasing length of bone; at the end of puberty this growth stops and appositional growth may continue.

Appositional Growth

For increasing thickness (width) of bone; continues after puberty; Process--Differentiation of cells at the periosteum and form bony ridges, Osteoblast become osteocytes and are surrounded by bony matrix, Extracellular matrix ridges surround periosteal blood vessels; Osteoclast in endosteum break down tissue and create larger medullary cavity.

Epiphyseal Plates

Plates between diaphysis and the two epiphyses that are made of hyaline cartilage; chondrocytes in the plates divide and secrete extracellular matrix which increase the length of the bone; hormones cause these plates to grow and become ossified.

Epiphyseal Line

developes in the region where epiphyseal plate existed; this line indicates the linear bone growth is no longer possible; premature ossification of this plate may result in unequal bone lengths.

Bone Remodeling

Bone continually undergoes changes; a continuous process of resorption and deposition that occurs in bone; allows for healing of broken bone; More stress means thicker bones (more deposition). (more lbs, bigger bones).

3 Factors that Affect Bone Growth and Remodeling

1. Minerals
2. Vitamins
3. Hormones

Minerals

Typically calcium and phosphorous; smaller amounts of magnesium, fluoride, iron and manganese needed for remodeling and growth.

Vitamins

Vitamin C needed for normal production of collagen; Folic Acid and Vitamin B for protein production; Vitamin A stimulates osteoblasts.

Human Growth Hormones

Produced by anterior pituitary gland stimulates osteoblast, increase protein synthesis and cell division at the epiphyseal plate and periostum.

Thyroid Hormones

(T3 and T4) Promote the bone growth via osteoblast stimulation.

Sex Hormones

(Estrogen and Androgens ) initially stimulate stimulate bone growth but as their secretion increase, epiphyseal plates become ossified to form epiphyseal lines.

Fracture

Any break in the bone

Closed or Simple

Simple bone break; bones that protrude out of the muscle and skin

Open or Compound

Fracture where bone punctures skin

Comminuted

ends of broken bones splinter leaving fragments between broken ends

Greenstick

bones "bend" rather than breaking cleanly; seen in children

Impacted

broken end of one bone driven into another bone

Pott's fracture

fracture of distal fibula, usually resulting in damage to medial aspect of ankle joint

Colle's fracture

fracture of distal radius often seen upon falling on outstretched arm

Stress fractures

Microscopic fractures seen with repeated stress to bones.

4 Steps to Bone Fracture Repair

1. Production of Fracture Hematoma
2. Formation of Fibrocartilage callus
3. Bony callus produced; external callus
4. Bone remodeling

Fracture Hematoma

A large blood clot that develops several hours after the fracture.

Edema

Swelling

Production of Fracture Hematoma

fracture cause damage to blood vessels and nerves; Hematoma; Pain; Inflammation and Edema; Phagocytes ad asteoclasts begin to clean damaged/dead tissue.

Formation of Fibrocartilage Callus

Fibroblasts move from the periosteum to the fracture site; deposit of collagen fibers; osteoblast cells in the periosteum begin to produce fibrocartilage callus that provides support

Bony callus produced

osteoblasts begin to deposit bony matrix forming spongy bone; bony callus replaces fibrocartilage callus

Bone remodeling

Spongy bone is replaced with compact bone at the periphery. Damaged tissue is removed by osteoclasts.

Calcium

Bone is storage site for most of the this in body; This is involved in blood coagulation, nerve conduction, muscle contraction and certain enzymatic reactions

Blood Coagulation

Clotting of Blood

Parathyroid Hormone (PTH)

Produced to increase blood calcium levels; stimulates osteoclast activity resulting in bone resorption; calcium homeostasis

Calcitonin (CT)

Produced by parafollicular cells of thyroid gland; functions to decrease blood calcium levels; inhibits osteoclast; stimulates bone deposition and calcium uptake.

Demineralization

Loss of bone mass resulting from the loss of calcium and other minerals; Effects menopausal women due to decreased levels of estrogen, but men have continued production of testosterone so they are at a lower risk.

Decreased protein synthesis

Results in brittleness of bones.

Osteoporosis

decreased bone mass; menopausal women due to decreased estrogen; risk include family, diet, small build, sedentary life, smoking, drinking, or Caucasian/asian ethnicity.

Osteoporosis Treatment

Hormone replacement therapy for menopausal women; calcium supplementation

Giantism

overproduction of (Human Growth Hormone) HGH during early childhood years.

Pituitary dwarfism

underproduction of human growth hormone during early childhood years

Acromegaly

overproduction of human growth hormone after puberty leading to selective thickening of facial, hands, and feet bones

Marfan's syndrome

mutation that causes excessive cartilage in the epiphyseal plates; disproportionate, longer arms and legs; associated with cardiovascular problems

Achondroplasia

mutation that expresses as lack of cartilage growth that leads to unusually short arms and legs

Osteogenesis imperfecta

genetic disorder that causes deficiency of fibers in the bone matrix; bones become brittle and fracture easily.