Osteology & The Skeletal System
Terms
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- How many named bones are there?
- 206
-
How many bones are you born with?
What happends to them? - Actually born with approximately 300 bones, but a number of these fuse during growth and development
-
What is the longest bone in the body?
Shortest bone in the body? -
Longest= Femur (also strongest)
Shortest= Stapes(in the ear) -
BONE
Characteristics of? -
Is a type of tissue
Variety of shapes, sizes, functions
Made up of a variety of cell types - BONES: Classification of: By Group
-
2 Main Groups
Axial (Skull, Ribs, Vertebrae)
Appendicular (Extremeties & Pelvis) - OSTEOLOGY
- The study of the formation of bone
-
BONE: Classification: By Shape
Name them all -
Long Bones
Short Bones
Flat Bones
Irregular bones - LONG BONES
-
Longer than they are wide
Ex. humerus, femur, phalanges, radius, ulna, etc. - SHORT BONES
-
cube shaped bones of the wrist &
ankle
bones that form within tendons
(ex. patella) - FLAT BONES
-
thin, flattened, & a bit curved
(sternum, skull bones) - IRREGULAR BONES
-
bones with complicated shapes
(ex. vertebrae, hip bones) - FUNCTION OF BONES
-
Support (bones are primary support
involved in sitting, standing, etc)
Protection (ex. skull, thorax, vertebrae
Movement (ex. levers, joints)
Mineral Storage (resevoir for Ca, P)
Hematopoiesis ( formation of BC) -
BONE STRUCTURE
Compact Bone -
The external layer
Visible part of bone - What is the structural unit of compact bone?
- Osteon
-
BONE STRUCTURE
OSTEON
description
function -
Elongated cylinder oriented parallel
to long axis of the bone
Grouping of bony tubes (called
lamellae)
Serves as weight bearing pillars -
BONE STRUCTURE
How are collagen fibers arranged in the lamellae?
What is the purpose of this? -
Collagen fibers in alternating lamellae run in alternating directions
This allows for great resistance to torsional stress -
BONE STRUCTURE
Haversian canal
what is it?
location -
A canal filled with a blood vessel & a
nerve
Located in the osteon -
BONE STRUCTURE
Volkmans Canal
what is it
location
which way does it run? -
Canal that connects the blood supply
of the osteon to the fibrous covering
of bone called the periosteum.
Osteon
Runs left & right. perpendicular -
BONE STRUCTURE
Osteocytes
what are they
where are they found -
Mature bone cells
Lie on the edge of the lamellae (in
the osteon) -
BONE STRUCTURE
CANALICULI -
tiny canals through which Cell to cell connections occur
Allows for cel to cell communication & transport of nutrients & waste -
SPONGY BONE
What does it contain?
Where does it accumulate?
What is its function? -
Contains bony struts called
traneculae (only few cells thick)
Occur in areas of stress points
Built to provide structural stability (similar to the idea of an arch) -
CHEMICAL COMPOSITION OF BONE
Is bone made of organic or inorganic constituents? -
Contains both organic & inorganic
constituents -
ORGANIC CONSTITUENTS OF BONE
What is it comprised of?
What does osteoid do?
What does collagen do? -
Comprised of osteoid (glycoproteins,
proteoglycans & collagen fibers-main component) &
several types of bone cells
Osteoid contributes to flexibility & strength of bone
Collagen forms sacrificial bonds that help to dissipate energy -
INORGANIC CONSTITUENTS OF BONE
describe it
what is it comprised of
what may it also contain? -
Tightly packed crystals of mineral salts called hydroxyapatite
Comprised mostly of calcium phos
phate
May also contain Mg, Na, K, Carbona
te, & heavy metals -
INORGANIC CONSTITUENTS OF BONE
Mechanism of deposition?
Function? -
Polymerization (can connect with
each other to form long chains) of
collagen
Allows for calcium salt precipitation,
& formation of HAP crystals -
SKELETAL TISSUE CELLS: OSTEOBLASTS
Where is it derived from?
Function?
What does it contain?
Where is it located -
Derived from the mesenchyme
Function: secretes components of
osteoid, contains important matrix
proteins, mineralizes osteoid.
Contains proteins: osteocalcin,
osteopontin (binds calcium,
promotes mineralization)
Organic portion of bone -
SKELETAL TISSUE CELLS: OSTEOCLASTS
what are they?
what are they similar to?
function?
what does it contain? -
Multinucleate cells, derived from
bone marrow.
Similar to macrophages
F: bone resorption (combine to bone
using integrins to hold on to bone)
Contains intracytoplasmic acidifying
vesicles that demineralize bone - What happends to the bone when there is too much resorption?
- Weakened, brittle bone
-
SKELETAL TISSUE CELLS: OSTEOCYTES
Derived from?
Contains?
Function?
What does strain do? -
Derived from "trapped" osteoblasts
(only until signaled back into osteo
blasts)
Contains: Sensory cells that form a
network of communication with the
bone
F: May act as mechanosensory cells
F: Conveys info relating to the
microenvironment of the neighborin
bone
Strain may initiate signaling of
osteoblasts/osteoclasts -
BONE MARROW
How many types of bone marrow are there?
What are they called? -
2 Types
Red
Yellow -
YELLOW MARROW
What is it?
What is its function? -
Mostly adipose tissue
Used as an energy reserve -
RED MARROW
Contains? - Contains pluripotential stem cells from which all circulating blood cells are derived
- STEM CELLS
- Undifferentiated cells that can be signalled to make necessities
-
STEM CELLS DIFFERENTIATION: PROERYTHROBLASTS
what are they?
where do they develop?
what do they develop into?
how many generations?
what does it regulate? -
Newly forming immature RBCs
Develop in the bone marrow into erythrocytes
Several generations, each successive step gains more Hgb
Regulation: erythropoietin - ERYTHROCYTES
-
Anucleate
Short living because of no nucleus so they must constantly reproduce -
ERYTHROPOIETIN
what is it
what does it do
what does it secrete? -
hormone
promotes formation of proethryroblas
ts
secreted by kidneys when 02 levels
are low -
MEGAKARYOCYTES
what is it?
what is it regulated by? -
Huge cell type that gets fragmented
into smaller cells called platelets
Regulated by thrombopoietin &
interleukins -
PLATELETS
what are they?
what is a special feature of them? -
Fragments of a cell, not cells of their
own
Anucleate
Biochemically active -
PHAGOCYTIC CELLS
what does it produce?
What does it regulate? -
Produce a wide variety of WBCs
Regulates granulocyte Stimulating
Factor (secreted by other cells) -
WHITE BLOOD CELLS
what is their primary role?
Example? -
Predominately involved in immunity
(ex. anitbodies) -
LYMPHATIC CELLS
what are they? - B & T Cell pathways
-
B CELLS
what are they
what do they do? -
Immunoglobulin secreting
Signals T cells to come & kill the
antigen -
T CELLS
what are they?
where do they travel?
what is so special about these cells -
Killer Cells
Travel through thymus glands
They are the only cells that can
recognize the difference between
good cells & antigens. -
HORMONE CONTROL
Name 3 ways hormones are
controlled in bone -
Bone Growth
Bone Remodeling
Calcium Homeostasis -
BONE GROWTH
what is it stimulated by?
What are the steps of bone growth? -
Stimulated by Growth Hormone (GH)
1. Secreted by Anterior Pituitary
2. GH binds to liver
3. GH secretes insulin growth factor
(IGF-1)
4. IGF-1 binds to cartilage & stimul
ates movement of chondroblasts
from G1 to S phase. - CALCIUM HOMEOSTASIS
-
Maintained by the parathyroid horm
one -
PARATHYROID HORMONE
what is it secreted by?
what does it increase/decrease? -
secreted by parathyroid gland
increases calcium reabsorption from
bone
decreases renal calcium excretion -
PARATHYROID GLAND
where is it located?
what does it contain?
what does it secrete? -
Located near thyroid gland but can
be ectopic (in chest)
Contains calcium receptors that
signal to either make more or less
calcium
Secretes parathyroid hormone -
CALCITONIN
secreted by?
what does it reduce/decrease? -
Secreted by parafollicular cells of the
thyroid
Reduces calcium levels in the blood
decreases osteoclast activity
decreases formation of new osteocl
asts -
BONE HEALTH
Name the molecules that contribute
to bone health -
Vitamin A
Vitamin D
Vitamin C
Alkaline Phosphate -
VITAMIN A
why is this important for bone health -
Important in the balance of mineral
deposition & resorption as well as
cell growth -
VITAMIN D
what does it do? -
Acts as a steroid in the intestine to
increase the production of a
transporter protein which increases
calcium absorption -
VITAMIN C
what does it do?
what is a unique characteristic about it?
where is it located? -
involved in collagen synthesis
water soluble
Makes up organic portion of bone -
ALKALINE PHOSPHATE (ALP)
Secreted by?
what is it?
what does it do? -
Secreted by osteoblasts, kidneys, &
other organs
It is an enzyme that is essential for
collagen mineralization
ALP splits phosphorous compounds
which can combine with calcium to
form Hydroxyapatite (HAP) -
OSTEOGENESIS
what does it mean?
how many types are there?
what are the types? -
bone formation & growth
2 types
intramembranous & endochondral -
INTRAMEMBRANOUS
what is it? - bone formation from fibrous tissue
-
ENDOCHONDRAL
what is it? - bone fromation from hyaline cartilage
-
ENDOCHONDRAL OSSIFICATION
when does it begin?
how does it know where to form bone?
what does it require? -
-begins in the second month of development
-uses hyaline cartilage "bones" as models for bone construction
-requires breakdown of hyaline cartilage prior to ossification -
STAGES OF INTRAMEMBRANOUS
OSSIFICATION
explain the 4 stages -
1. An ossification center appears in the fibrous connective tissue membrane
2.bone matrix is secreted w/in fibrous tissue
3.Woven bone & periosteum form
4.Bone collar of compact bone forms & red marrow appears - WHAT IS AN OSSIFICATION CENTER?
- place where bones form
-
STAGES OF ENDOCHONDRAL OSSIFICATION
explain the 5 stages -
1. Formation of bone collar
2. Cavitation of the hyaline cartilage
3.Invasion of internal cavities by
periosteal bud & spongy bone formtn
4.Formation of medullary cavity, appearance of secondary ossification centers in epiphyses
5. Ossification of epiphyses, with hyaline cartilage remaining only in the epiphyseal plates. -
POSTNATAL BONE GROWTH
name 3 things that happen in terms of growth in the length of long bones -
Growth in length of long bones
*cartilage on side of epiphyseal plate closest to epiphysis is relatively inactive
*cartilage abutting shaft of bone organizes into pattern that allows fast, efficient growth
*cells of epiphyseal plate proximal to resting cartilage form 3 functionally different zones: growth, transformation, & osteogenic -
FUNCTIONAL ZONES IN LONG BONE GROWTH
Growth Bone -
Cartilage cells undergo mitosis,
pushing epiphysis away from diaphysis -
FUNCTIONAL ZONES IN LONG BONE GROWTH
Transformation Zone - older cells enlarge, matrix becomes calcified, cartilage cells die, matrix begins to deteriorate
-
FUNCTIONAL ZONES IN LONG BONE GROWTH
Osteogenic Zone - new bone formation occurs
-
LONG BONE GROWTH
what happends here? - cartilage continulally grows and is replaced by bone
-
REMODELING
what happends to bone here? - bone is resorbed & added by appositional growth