VIP Call Girls Lucknow Nandini 7001305949 Independent Escort Service Lucknow
Basics of skeletal system
1.
2. The Skeletal System
Topics to be covered
Functions of Bone and Skeletal System
Structure of Bone
Histology of Bone Tissue
Blood and Nerve Supply of Bone
Bone Formation
Bone’s Role in Calcium Homeostasis
Aging and Bone Tissue
3.
4. Functions of Bone and Skeletal System
4. Mineral Homeostasis:
Calcium balance: contribute to bone strength; stores
99% of body’s calcium;
Phosphorus balance: stored in bones and releases it on
demand of the body
5.
6.
7.
8.
9.
10. Histology of Bone Tissue
Four types of cells are present in bone tissue Osteogenic cell
Osteogenic cells
Undergo cell division; the resulting cells
develop into osteoblasts
Osteoblasts
Bone-building cells Osteoblast
Synthesize extracellular matrix of bone tissue
Osteocytes
Mature bone cells, maintains bone tissues
Exchange nutrients and wastes with the blood
Osteoclasts
Osteocytes
Release enzymes that digest the mineral
components of bone matrix (resorption)
Regulate blood calcium level
Osteoclast
11.
12. Bone Formation
The process by which bone forms is called
ossification or osteogenesis
Bone formation occurs in four situations:
1. Formation of bone in an embryo
2. Growth of bones until adulthood
3. Remodeling of bone
4. Repair of fractures
13. 1. Formation bone
1. Development of the ossification center.
At site where bone develops specific chemical
messages cause mesenchymal cells to aggregate and
differentiate, first into osteogenic cells then
osteoblasts.
Blood capillary
Ossification center
Mesenchymal cell
Osteoblast
Collagen fiber
1 Development of ossification center
14. 1. Formation bone
2. Calcification:
Within a few days calcium and other mineral salts
are deposited and extracellular matrix becomes
calcified.
Osteocyte in lacuna
Canaliculus
Osteoblast
Newly calcified bone
matrix
2 Calcification
15. 1. Formation bone
3. Formation of trabeculae:
Extracellular matrix develops into trabeculae that
fuse with each other to form spongy bone
Blood vessels grow into the spaces
Connective tissue associated with blood vessels
differentiates into red marrow
Mesenchyme
condenses
Blood vessel
Spongy bone
trabeculae
Osteoblast
3 Formation of trabeculae
16. 1. Intramembranous ossification
4. Development of the periosteum:
In conjunction with formation of trabeculae, the
mesenchyme condenses at the periphery
Eventually a thin layer of compact bone replaces the
spongy bone, but spongy bone remains in the center
Much of the new bone is remodeled as the bone is
transformed into adult shape and size
Periosteum
Spongy bone tissue
Compact bone tissue
4 Development of the periosteum
17. Bone Growth During Infancy, Childhood
and Adolescence
Growth in Length
The growth in length of long bones
involves four major events:
1. Growth of cartilage on the
epiphyseal plate
2. Replacement of cartilage by bone
tissue in the epiphyseal plate
3. The activity of the epiphyseal plate
is the way bone can increase in
length
4. At adulthood, the epiphyseal plates
close and bone replaces all the
cartilage leaving a bony structure
called the epiphyseal line
18. Bone Growth During Infancy, Childhood and
Adolescence
Growth in Thickness
Bones grow in thickness at the outer surface
Remodeling of Bone
Bone forms before birth and continually renews
itself
The ongoing replacement of old bone tissue by new
bone tissue
Old bone is continually destroyed and new bone is
formed in its place throughout an individual’s life
19.
20. Factors Affecting Bone Growth and Bone
Remodeling
Normal bone metabolism depends on several factors
Minerals
Large amounts of calcium and phosphorus and smaller
amounts of magnesium, fluoride, and manganese are
required for bone growth and remodeling
Vitamins
Vitamin D helps build bone by increasing the absorption
of calcium from foods in the gastrointestinal tract into
the blood
Vitamins K are also needed for synthesis of bone
proteins
21. Bone’s Role in Calcium Homeostasis
Bone is the body’s major calcium reservoir
Levels of calcium in the blood are maintained by
controlling the rates of calcium resorption from
bone into blood and of calcium deposition from
blood into bone
Both nerve and muscle cells depend on calcium ions
(Ca2+) to function properly
Blood clotting also requires Ca2+
Many enzymes require Ca2+ as a cofactor
22. Bone’s Role in Calcium Homeostasis
Actions that help elevate blood Ca2+ level
Parathyroid hormone (PTH) regulates Ca2+
exchange between blood and bone tissue
PTH increases the number and activity of osteoclasts
PTH acts on the kidneys to decrease loss of Ca2+ in the
urine
PTH stimulates formation of calcitriol a hormone
that promotes absorption of calcium from foods in
the gastrointestinal tract
23.
24. Bone’s Role in Calcium Homeostasis
Actions that work to decrease blood Ca2+ level
The thyroid gland secretes calcitonin (CT) which
inhibits activity of osteoclasts
The result is that CT promotes bone formation and
decreases blood Ca2+ level
Accelerates uptake of calcium and phosphate into bone
matrix
25. Exercise and Bone Tissue
Bone tissue alters its strength in response to
changes in mechanical stress
Under stress, bone tissue becomes stronger through
deposition of mineral salts and production of collagen
fibers by osteoblasts
Unstressed bones diminishes because of the loss of bone
minerals and decreased numbers of collagen fibers
The main mechanical stresses on bone are those
that result from the pull of skeletal muscles and
the pull of gravity
Weight-bearing activities help build and retain
bone mass
26. Aging and Bone Tissue
The level of sex hormones diminishes during
middle age, especially in women after menopause
A decrease in bone mass occurs
Bone resorption by osteoclasts outpaces bone
deposition by osteoblasts
Female bones generally are smaller and less
massive than males
Loss of bone mass in old age has a greater adverse effect
in females
27. Aging and Bone Tissue
There are two principal effects of aging on bone tissue:
1) Loss of bone mass
Results from the loss of calcium from bone matrix
The loss of calcium from bones is one of the symptoms in osteoporosis
2) Brittleness
Results from a decreased rate of protein synthesis
Collagen fibers gives bone its tensile strength
The loss of tensile strength causes the bones to become very brittle and
susceptible to fracture