Download Ch 6 Bone Tissue Notes

Chapter 6
The Skeletal System: Bone Tissue
Lecture Outline
Principles of Human Anatomy and Physiology, 11e
1
INTRODUCTION
• Bone is made up of several different tissues working together.
• Each individual bone is an organ; the bones, along with their
cartilages, make up the skeletal system.
• The study of bone structure and the treatment of bone
disorders is called osteology.
2
Functions of Bone
• Supporting soft tissues, providing an
attachment site for tendons and muscles
• Protects internal organs from injury
• Work with muscles to produce movement
• Storage of minerals like calcium & phosphate
• Blood cell production occurs in red bone
marrow
• Energy storage (triglycerides) in yellow bone
marrow
Principles of Human Anatomy and Physiology, 11e
3
Bone Anatomy
• A long bone is one that has greater length than width.
Principles of Human Anatomy and Physiology, 11e
4
Anatomy of a Long Bone
• Diaphysis = shaft: the
long, cylindrical main
portion of the bone
• Epiphysis = either end of
a long bone
• Metaphyses are the areas
between the epiphysis
and diaphysis
Principles of Human Anatomy and Physiology, 11e
5
Anatomy of a Long Bone
• Articular cartilage is a thin
layer of cartilage that forms
a joint where two bones
connect.
• Periosteum is a tough
connective tissue covering
that surrounds a bone.
Principles of Human Anatomy and Physiology, 11e
6
Anatomy of a Long Bone
• The medullary cavity
or marrow cavity is
the space in the
diaphysis that stores
yellow bone marrow.
• The endosteum is a
thin membrane that
lines the medullary
cavity.
Principles of Human Anatomy and Physiology, 11e
7
HISTOLOGY OF BONE TISSUE
• Bone (osseous) tissue consists of widely separated cells
surrounded by large amounts of matrix.
• The matrix of bone is made up of water, collagen, and salts.
• These salts are used to form new bone tissue, which is called
calcification.
8
Bone Marrow
• Red bone marrow
produces red blood cells,
white blood cells, and
platelets
• Yellow bone marrow
stores triglycerides (fats)
which are used for
energy
9
Bone Cells (4)
1. Osteogenic cells are stem cells that can undergo cell division and
become other bone cells.
2. Osteoblasts are bone-building cells.
3. Osteocytes are mature bone cells and the principal cells of bone
tissue. They maintain bone metabolism, and exchange nutrients
and wastes with the blood.
4. Osteoclasts are large cells that are used for bone development,
growth, maintenance, and repair
10
Types of Bone
• 80% of your skeleton is made of compact bone.
• 20% is spongy bone.
Principles of Human Anatomy and Physiology, 11e
11
Compact Bone
• Compact bone contains few
spaces and is the strongest
type of bone.
• It makes up the bulk of long
bones
• It provides protection and
support, and resists the
stresses of weight and
movement
• It is made of osteons, hard
rings of material
Principles of Human Anatomy and Physiology, 11e
12
Spongy Bone
• Spongy bone does not contain osteons. It
consists of thin columns of bone with
many red marrow filled spaces.
• It forms most of the structure of short,
flat, and irregular bones, and the
epiphyses of long bones.
• Spongy bone tissue is light and supports
and protects the red bone marrow.
• Hip bones, rib bones, the breastbone,
vertebrae are types of spongy bones
Principles of Human Anatomy and Physiology, 11e
13
Blood and Nerve Supply of Bone
• Periosteal arteries
– supply periosteum (outer
part of bone)
• Nutrient arteries
– Supplies inner bone and red
marrow
• Veins carry blood away from
the bone and back to the heart.
• All bones have sensory nerves
attached to them.
14
BONE FORMATION
• Bone formation is termed osteogenesis or ossification
– 1. Formation of the bony skeleton. (embryonic development)
– 2. Bone Growth (childhood into early adulthood)
– 3. Bone Remodeling and Repair (adulthood)
• Two types of ossification occur.
– Intramembranous ossification
– Endochondrial ossification
Principles of Human Anatomy and Physiology, 11e
15
Intramembranous Ossification
• The flat bones of the skull and
the jaw are formed this way.
• These bones develop from
fibrous membranes.
• 1. A cluster of cells, called the
ossification center, and form
osteoblasts.
• 2. Osteoblasts become
osteocytes, and harden (calcify)
• 3. Blood vessels grow into
place.
• 4. The periosteum (membrane)
grows over the bone.
Principles of Human Anatomy and Physiology, 11e
16
Endochondral Ossification
• Endochondral ossification is the replacement of cartilage by bone. Most
bones in the body form this way.
• 1. Cartilage forms in the shape of the bone.
• 2. An ossification center forms, and begins to grow osteoblasts.
• 3. The marrow cavity forms.
• 4. New ossification centers form at each epiphysis, so bones can
continue to elongate.
Principles of Human Anatomy and Physiology, 11e
17
Growth in Length
• Bones grow only at the epiphyseal plate which is located in
the metaphysis of a growing bone.
• Between ages 18 to 25, epiphyseal plates close.
• Growth in length stops at age 25
Principles of Human Anatomy and Physiology, 11e
18
Growth in Thickness
•
•
•
•
Bone can increase in diameter through appositional growth.
Osteoblasts grow outward and form hardened ridges
These ridges fold over and become osteons (rings)
The marrow cavity enlarges.
Principles of Human Anatomy and Physiology, 11e
19
Bone Remodeling
• Remodeling is the ongoing replacement of old bone tissue
by new bone tissue.
– Old bone is constantly destroyed by osteoclasts (bone
resorption), whereas new bone is constructed by
osteoblasts (bone deposition).
– 20% of spongy bone and 4% of compact bone is
remodeled each year!
– This can be triggered by exercise, diet, or lack of
exercise.
20
Factors Affecting Bone Growth
• Nutrition
– adequate levels of minerals and vitamins
• calcium and phosphorus for bone growth
• vitamin C for collagen formation, Vitamin A for
osteoblasts
• vitamins K and B12 for protein synthesis
21
Factors affecting Bone Growth
• Sufficient levels of specific hormones
– during childhood need insulin like
growth factor (IGF)
– Human Growth Hormone (too
much=gigantism, not enough=pituitary
dwarfism)
– sex steroids at puberty
– At puberty the sex hormones,
estrogen and testosterone, stimulate
sudden growth and modifications of
the skeleton to create the male and
female forms (wider pelvis).
22
Bone Scan
• A bone scan is a diagnostic technique for viewing bones.
– A radioactive tracer is injected through an IV
– A scanner measures blood flow to areas of the bone
– Dark areas (more blood flow) may indicate cancer
– Light areas (less blood) may indicate arthritis or bone
loss.
23
Braces
– In orthodontics teeth are moved by braces.
– This places stress on bone in the sockets causing
osteoclasts and osteoblasts to remodel the sockets so
that the teeth can be properly aligned.
Principles of Human Anatomy and Physiology, 11e
24
Fracture and Repair of Bone
A fracture is any break in a bone.
• Fractures are named according to their severity, the shape
of the fracture, or the physician who first described
fractures.
Principles of Human Anatomy and Physiology, 11e
25
Common Fractures
•
•
•
•
Open/Compound Fracture: Broken bones protrude through skin
Closed Fracture: Broken bones do NOT show through
Comminuted fracture: Bone splinters at site of impact
Greenstick Fracture: One side of the bone breaks, the other
bends (only occurs in children)
• Impacted fracture: One bone is driven into another
Principles of Human Anatomy and Physiology, 11e
26
Common Fractures
• Pott’s fracture: fracture of the fibula (leg bone)
• Colles’ fracture: fracture of the forearm bone
• Stress fracture: Microscopic fissures but no broken bones
– Results from repeated, strenuous activity like running,
jumping, or dancing
Principles of Human Anatomy and Physiology, 11e
27
Fracture & Repair of Bone
• Healing is faster in bone than in cartilage since bones have
better blood supplies
• Healing of bone is still slow process due to vessel damage
• Clinical treatment:
– closed reduction = restore pieces to normal position by
manipulation
– open reduction = realignment during surgery
• Both are followed by immobilization in a cast, sling, or
bandage
28
Repair of a Fracture
• 1. Formation of fracture hematoma
– Damaged blood vessels produce a clot
• 2. Formation of fibrocartilagenous callus
– Collagen and cartilage fibers span the break
Principles of Human Anatomy and Physiology, 11e
29
Repair of a Fracture
• 3. Formation of bony callus
– osteoblasts secrete spongy bone
– lasts 3-4 months
• 4. Bone remodeling
– compact bone replaces the spongy in the bony callus
– surface is remodeled back to normal shape
30
Calcium Homeostasis & Bone Tissue
• Skeleton is a reservoir of Calcium & Phosphate
• Calcium ions involved with many body systems
– nerve & muscle cell function
– blood clotting
– enzyme function in many biochemical reactions
• Small changes in blood levels of Ca+2 can be deadly
– cardiac arrest if too high
– respiratory arrest if too low
Principles of Human Anatomy and Physiology, 11e
31
EXERCISE AND BONE TISSUE
• Within limits, bone has the ability to alter its strength in
response to mechanical stress by increasing deposition of
mineral salts and production of collagen fibers.
– Removal of mechanical stress leads to weakening of
bone through demineralization (loss of bone minerals)
and collagen reduction.
• reduced activity while in a cast
• astronauts in weightless environment
• bedridden person
– Weight-bearing activities, such as walking or moderate
weightlifting, help build and retain bone mass.
Principles of Human Anatomy and Physiology, 11e
32
AGING AND BONE TISSUE
• Loss of calcium which may result in osteoporosis.
– very rapid in women 40-45 as estrogens levels decrease
– in males, begins after age 60
• Decreased rate of protein synthesis
– decrease in collagen production which gives bone its
tensile strength
– decrease in growth hormone
– bone becomes brittle & susceptible to fracture
Principles of Human Anatomy and Physiology, 11e
33
Osteoporosis
• Decreased bone mass resulting in porous bones
• Those at risk
– white, thin menopausal, smoking, drinking female with family
history
– athletes who are not menstruating due to decreased body fat
& decreased estrogen levels
– people allergic to milk or with eating disorders whose intake
of calcium is too low
• Prevention or decrease in severity
– adequate diet, weight-bearing exercise, & estrogen
replacement therapy (for menopausal women)
– behavior when young may be most important factor
Principles of Human Anatomy and Physiology, 11e
34
• Osteoarthritis
• degenerative arthritis or degenerative joint disease
• caused by 'wear and tear' on a joint
• Cartilage breaks down and wears away then the bones
rub together, causing pain, swelling, and stiffness.
• Factors: age, weight, sports, previous injuries.
• Rheumatoid Arthritis
• A disease that leads to inflammation of the joints and
surrounding tissues.
Principles of Human Anatomy and Physiology, 11e
35
Disorders of Bone Ossification
• Rickets
• calcium salts are not deposited properly
• bones of growing children are soft
• bowed legs, skull, rib cage, and pelvic deformities result
• Osteomalacia
• new adult bone produced during remodeling fails to
ossify
• hip fractures are common
36
Diseases and Disorders of the Bone
• Submit a 1-2 page, TYPED report, due Monday 10/29.
•
•
•
•
•
•
•
1. Describe the disease/disorder.
2. What causes this to happen?
3. Are there certain groups more at risk than others?
4. What are some treatments? Cures?
5. Describe the impact on the life of someone affected.
6. Are there support groups?
7. REFERENCES!!!!
37