Unit 3 Part 1 Flashcards
made up of several different tissues working together: bone, cartilage, dense connective tissue, epithelium, various blood forming tissues, adipose tissue, and nervous
tissue.
Bone
Skeletal System Functions
▪ Makes up body framework - gives body shape
▪ Supports the body
▪ Protects vital internal organs
▪ Assistance in movement
▪ Mineral homeostasis (storage and release)
▪ Blood Cell production
▪ Triglyceride storage
Classification of Bones is according to:
shape
location
structure
development
Classification of Bones According to Shape
long
short
flat
irregular
sesamoids
sutural
– longer than wide
– Have a shaft with heads at both ends
– Contain mostly compact bone
Long Bones
Examples of long bone
Femur, humerus, tibia,
fibula, radius, ulna, phalanges (all
bones of the limbs except the knee
cap or patella)
- Shaft
- Composed of compact bone
Diaphysis
- Ends of the bone
- Composed mostly of spongy bone
Epiphysis
- Outside covering of the diaphysis
- Fibrous connective tissue membrane
Periosteum
- Secure periosteum to
underlying bone
Sharpey’s fibers
- Supply bone cells with
nutrients
Arteries
– Covers the external surface of the epiphyses
– Made of hyaline cartilage
– Decreases friction at joint surfaces
Articular cartilage
– Cavity of the shaft
– Contains yellow marrow (mostly fat) in adults
– Contains red marrow (for blood cell formation) in infants
Medullary cavity
formation of blood cells
hematopoiesis
formation of blood cells takes place mainly in
red marrow
In infants, red marrow is found in the
bone cavities
Red marrow functions
formation of red blood cells, white blood cells
and blood platelets
– cube-shape
– Contain mostly spongy bone with thin coat of
compact bone
Short Bones
example of short bones
carpals (wrist), tarsal (ankle) bones
– Irregular in shape, weird shapes
– Do not fit into other bone classification
categories
Irregular Bones
examples of irregular bones
Vertebrae, hip bones, 2 skull bones (sphenoid
and the ethmoid bones)
Develop in certain tendons where there is considerable
friction, tension and physical stress
Sesamoid bones
-Located in sutures between certain cranial bones
Sutural bones
Structure of Short, Irregular, and Flat Bones
-Thin plates of periosteum-covered compact bone on
the outside and endosteum-covered spongy bone
within.
- Have no diaphysis or epiphysis
-Contain bone marrow without marrow cavity
internal spongy bone layer
diploë
whole arrangement of flat bone resembles a
stiffened sandwich
form the long axis of the body
Axial
number of bones in axial
80
Involved in locomotion and manipulation of the environment
appendicular
number of bones in upper extremities
64
number of bones in lower extremities
62
connective tissue as seen by widely spaced cells separated by matrix
osseus tissue/bone
4 types of cells in bone tissue
Osteogenic/Osteoprogenitor Cells
Osteoblasts
Osteocytes
Osteoclasts
- undergo cell division
- undifferentiated/unspecialized bone cells derived from mesenchyme
- become osteoblasts
- found in the inner lining of the endosteum and periosteum
Osteogenic/Osteoprogenitor Cells
- Bone-building cells
- Cannot divide
- Form matrix and collagen fibers
- Synthesize and secrete collagen fibers and proteoglycans, glycoproteins
- Collagen forms osteoids
- Influence deposit of Ca++, PO4 (initiate calcification)
- Estrogen, PTH stimulate activity
- Found in both the periosteum and endosteum
Osteoblasts
strands of spiral fibers that form matrix
osteoids
- Mature bone cells that sit in lacunae and the
principal cells of bone tissue - Osteoblasts that have become trapped by the secretion of matrix
- No longer secrete matrix
- Responsible for maintaining the bone tissue; long lived cells
- Stimulated by calcitonin; inhibited by PTH
- Osteocyte is “trapped” within the pink matrix
Osteocytes
- derived from the fusion of monocytes – engulf bony material
- Cells that digest bone matrix
- Secrete enzymes (digestive enzymes) that digest matrix
- Active osteoblasts stimulate its activity
- Concentrated in the endosteum
pumps out hydrogen ions to create an acid environment that eats away at the matrix.
Osteoclasts
- 25% Water
- 25% Protein or organic matrix
- 90% Collagen Fibers
- 10% Chondroitin Sulfate, small proteogylcans, glycoproteins (osteonectins)
- 50% Crystalized Mineral Salts
- Hydroxyapatite (Calcium Phosphate)
- Other substances: Bicarbonate, magnesium,
potassium, sodium, Lead, Gold, Strontium,
Plutonium, etc.
Extracellular Matrix
provide bone’s hardness and the ability to resist compression
Inorganic mineral salts
provide bone’s flexibility
Organic collagen fibers
Bone Tissue - Matrix
– compact bone has very few such spaces
– spongy bone has many such spaces
-solid mass; dense & hard
-forms the outer layer of bone structure
-functional unit — Haversian system
Compact bone
contain spaces filled with bone marrow
= incomplete Haversian system
Cancellous or Spongy
good at providing protection and support
Compact bone
lightweight and provides tissue support
Spongy bone
Compact bone is arranged in units called
osteons or Haversian systems
contain blood vessels, lymphatic vessels, nerves
Osteons (Haversian canal)
what surrounds haversian canal
concentric rings of osteocytes
calcified matrix
concentric ring of matrix lacuna-openings
between lamellae for osteocytes;
represent older osteons
Lamella
mature bone cell; found in lacunae
Osteocytes
in center of lamella; houses vessels; vertically oriented
Haversian canal
radiating channels between lacuna
and Haversian canal for nutrients and wastes
Canaliculi
crosswise canals from Haversian canal to exterior containing blood vessels and nerves
Volkmann canal
does not contain osteons.
consists of trabeculae surrounding many red marrow filled spaces
forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones
Spongy bone
Latticework of thin plates of bone
Found in ends of long bones and inside flat bones such as the hipbones, sternum, sides of skull, and ribs.
trabeculae
enter the diaphysis through Volkmann’s canals
accompanied by nerves
Periosteal arteries
enters the center of the diaphysis through a nutrient foramen.
nutrient artery
All embryonic connective tissue begins as
mesenchyme
bone tissue formation;
begins when mesenchymal cells provide the template for subsequent ossification.
Osteogenesis (ossification)
Stages of bone development
– Bone formation
– Postnatal bone growth
– Bone remodeling and repair
bone development that begins in the 2nd month of
development
bone formation
bone development until early adulthood
postnatal bone growth
lifelong bone development
Bone remodeling and repair
Bones form in 4 situations
- embryological and fetal development
- grow before adulthood
- remodel
- fractures heal
Two Types of Ossification
Intramembranous ossification
Endochondral ossification
-Membrane bone develops from fibrous membrane
- Forms flat bones
-Dermal ossification
-A connective tissue membrane is replaced by bone
Intramembranous ossification
normally occurs in the deeper layers of connective tissue of the dermis of the skin.
dermal/intramembranous ossification
intramembranous ossification process
Ossification centers appear in the fibrous connective tissue membrane.
Calcification
Formation of trabeculae
Development of periosteum
-replacement of cartilage by bone and forms most of the bones of the body
- development of the cartilage model.
-Begins in the second month of development
-Uses hyaline cartilage “bones” as models for bone construction
-Requires breakdown of hyaline cartilage prior to
ossification
Endochondral Ossification
Endochondral Ossification process
development of cartilage model
growth of cartilage model
development of primary ossification center
development of medullary(marrow) cavity
development of secondary ossification center
formation of articular cartilage and epiphysial plate
Bones grow in thickness
appositional growth
bones lengthen by the addition of bone material on the diaphyseal side of the epiphyseal plate
interstitial growth.
layer of hyaline cartilage in the metaphysis of a growing bone
Epiphyseal plate
important functional zones of Epiphyseal plate
– resting cartilage
– proliferating cartilage
– hypertrophic cartilage
– calcified cartilage
- nearest the epiphysis and consists of small, scattered chondrocytes.
- The cells do not function in bone growth; they anchor the epiphyseal plate to the epiphysis of the bone.
Zone of Resting Cartilage
- Slightly larger chondrocytes are arranged in stacks
- These chondrocytes undergo interstitial growth
- The chondrocytes in this zone divide to replace those that die
Zone of Proliferating Cartilage
- Consists of large maturing chondrocytes
arranged in columns
Zone of Hypertrophic Cartilage
- Only a few cells thick and consists mostly of
chondrocytes that are dead - Osteoclasts dissolve the calcified cartilage, and
osteoblasts and capillaries from the diaphysis invade
the area. - The osteoblasts replace the calcified cartilage
*becomes the new diaphysis that is firmly cemented
Zone of Calcified Cartilage
cartilage is replaced by bone on the
diaphyseal side of the plate.
the epiphyseal plates closes at what age
18 in females, 21 in males
With the appearance of the ___,
bone growth in length stops completely.
epiphyseal line
gradual process and the degree to which it occurs is useful in determining bone age, predicting adult height, and establishing age at death from skeletal remains, especially in infants, children, and adolescents.
Closure of the epiphyseal plate
healing process of fracture involves 3 different phases in 4 steps
-reactive phase is an early inflammatory phase.
-reparative phase: fibrocartilaginous callus formation
-reparative phase: bony callus formation.
-bone remodeling phase
Factors Affecting Bone Growth
- Minerals
- Vitamins
- Hormones
- Exercise
- Aging
- Makes bone matrix hard, bone
growth
Calcium
low blood calcium levels
Hypocalcemia
low blood calcium levels
Hypocalcemia
high blood calcium levels.
Hypercalcemia
Makes bone matrix hard, bone growth
Phosphorus
- Controls activity, distribution, and
coordination of osteoblasts/osteoclasts
Vitamin A
- For protein synthesis
Vitamin B12
Helps maintain bone matrix, deficiency leads to decreased collagen production
Vitamin C
disorder due to a lack of Vitamin C
Scurvy
Helps build bone by increasing calcium absorption from foods in the GIT; “Rickets an osteomalacia” disease
Vitamin D(Calcitriol)
For protein synthesis
Vitamin K
Promotes general growth; stimulates epiphyseal plate
activity
Stimulate osteoblasts, promote cell division at the
epiphyseal plate and in the periosteum, and enhance synthesis of the proteins needed to build new bone.
insulin-like growth factor
Promotes normal bone growth and
maturity by increasing synthesis of proteins.
Insulin
Promotes normal bone growth and maturity (stimulates osteoblasts); modulates activity of growth hormone
Thyroid Hormones
Increases osteogenesis at puberty and is
responsible for gender differences of skeletons;
End growth by inducing epiphyseal plate closure
Estrogen and Testosterone
increases osteoclast activity leading to bone resorption
and increase blood calcium
Parathyroid hormone (PTH)
hormone from the thyroid gland that increases the deposition of calcium by osteoblast and thus lowering blood calcium level
Calcitonin
loss of minerals
demineralization
decrease in protein
decrease in :
growth hormone
collagen production
bones become brittle and susceptible to fracture
ongoing replacement of old
bone tissue by new bone tissue
Bone Remodeling
Occurs where bone is injured or added
strength is needed
Bone Deposition
- Accomplished by osteoclasts
- Secretion of:
– Lysosomal enzymes that digest organic matrix
– Acids that convert calcium salts into soluble forms - Dissolved matrix is transcytosed
Bone Resorption
– grooves formed by
osteoclasts as they break down bone matrix
Resorption bays
Calcium
most abundant essential mineral in the human body
range of calcium in adult
8.6 to 10.3 mg/dL.
amount of calcium
99% in the bone and teeth.
1% is in the extracellular fluid and blood
reservoir for calcium and phosphate
skeleton
Calcium is necessary for
– Transmission of nerve impulses
– Muscle contraction
– Neurotransmitter and hormone release
– Blood coagulation
– Enzyme function
– Secretion by glands and nerve cells
– Cell division
– Membrane integrity and permeability
high changes in blood levels of calcium
Cardiac arrest
low changes in blood levels of calcium
Respiratory arrest
2 hormones that
antagonistically maintain blood [Ca2+] at
homeostatic levels
Parathyroid hormone
and calcitonin
Calcium regulation three tissues:
Bone ,intestine and kidney
three hormones
Parathyroid hormone, calcitonin, and activated vitamin D
- Secreted if blood calcium falls.
- It acts on bone, kidney and intestine.
Parathyroid Hormone
PTH decreases urinary Ca2+ excretion
and increases urinary phosphate excretion.
kidney
PTH increases calcitriol (active
form of Vitamin D) synthesis which increases
Ca2+ absorption in the small intestine
intestine
INCREASES BLOOD CALCIUM LEVELS
parathyroid hormones
Secreted from parafollicular cells of thyroid
If blood calcium gets too high, — “tone down” blood calcium levels.
-inhibits osteoclast activity
-Stimulates osteoblast activity .
Calcitonin
DECREASES BLOOD CALCIUM LEVELS
calcitonin
A lipid soluble vitamin.
PTH stimulates — synthesis
can be acquired from 2 sources
Vitamin D
stimulate absorption of Ca2+ from the intestine.
acts on osteoblasts
stimulates osteocytic osteolysis
1,25-(OH)2-D
“thy” up “high”
Parathyroid hormone (PTH)
- tone Ca++ down
-Ca++ come “on in”
Calcitonin
- tri to rise Ca ++
Calcitriol
At birth, most long bones are well ossified
except __
epiphyses
Bone mass decreases with age beginning in
4th decade
bone resorption predominates at
old age
