Ch. 1.1-1.6, 1.9, 6.1, 11.20, & 11.21
KIN 131: Systems Physiology I
Lecture 1: Intro to Physiology, the Skeletal
System, and Ca2+ Homeostasis
Jenna Benbaruj BHK, MSc
Broad Overview of the Course
To investigate physiology, we have to acknowledge and understand anatomy.
Anatomy: The study of the physical structure and shape of the body and its components
large bodily structures
• Gross Anatomy: the study of _______________(often
whole organ systems)
smal
l
erstructures
• Microscopic Anatomy: the study of ____________(often
at the cell
or tissue
level)
Physiology: The study of how living organisms function;
• Investigation of the mechanisms by which the body can do what it can do
• How parts of the body work together at various levels of organization
Pathophysi
ol
ogy
• _____________:
a sub-field of physiology that focuses on disease states
Structure and Function are intimately
di
ctates
related; Structure________function.
2
Levels of Physiology
a. Cellular Physiology: the study of function at the cellular level
b. Systemic Physiology: the study of function of whole organ systems
c. Pathology Physiology (Pathophysiology): the study of disease states; the effects of pathology
on cells, organs, organ systems, or the whole organism
Homeostasis is a defining feature of physiology
•
stable
Definition: the dynamic process of maintaining a _______
internal environment
•
stable and
Dynamic constancy: a given variable may fluctuate in the body in the short term, but is ______
predictable in the long term
_________
dynamic not static; small adjustments are continually
The internal environment of the body is ________,
made to allow for the body to meet new demands, adjust to new stressors
•
When considering reference values for physiological variables, they are often presented in normal ranges
3
Homeostasis
Homeostatic control systems are mechanisms that respond to any change in the
reaction to correct the change and
internal environment that requires a _________
maintain physiological variables within normal ranges
Steady state: a state in which a variable in a system is not changing, but energy
must be continuously added to maintain a stable, homeostatic condition
• Different from equilibrium, which is a state where the variable does not
require an input of energy to maintain constancy
4
Homeostasis – Application Question
Example: You are waiting outside for the 99 bus to UBC before your final exam. It is
mid-December, and it’s currently ~-10°C. Your internal body temperature is 37 °C
(the thermoregulatory set point). What reactions might your body do to generate
more heat and/or prevent heat loss?
sensoryreceptorssend si
gnal
sto brai
n, al
l
owi
ng to percei
ve thatyou'
re col
d, deci
de to puton
Voluntary action:___________________________________________________
anotherj
acket.
______________________________________________________________
shi
veri
ng, peri
pheralvasoconstri
cti
on. Eventual
l
yreach a poi
ntwhere rate ofheatgai
ni
sequal
Involuntary action: _______________________________________________
to rate ofheatl
oss.
____________________________________________________________________
_____________________________________________________________________
narrow bl
ood vesselwal
l
5
Homeostasis
Physiological Range
hypothermia
Too little
(down to ~35°C)
Set Point
(36.1 – 37.2°C)
Too much
(up to ~39.2°C)
hyperthermia
Peripheral vasodilation
and increased sweating
6
Reflex Arc – A Homeostatic Control Mechanism
i
nvol
untary ________
bui
l
t-i
n response to a particular stimulus
Reflex: a specific, _________,
• May or may not involve conscious awareness
medi
ati
ng a reflex
Reflex arc: the pathway _________
• The stimulus refers to a detectable change in the internal or
external environment
• This change is detected by a receptor
• The receptor sends a signal to the integrating center
along the afferent pathway
• The integrating center processes the signal and evokes a
response
• A signal is sent to an effector along the efferent pathway
Figure 1.8
The response resulting from a reflex doesn’t necessarily always
oppose the stimulus
_______
7
Feedback and Feedfoward Systems
anti
ci
pate a
after it has occurred, while feedforward systems ________
Feedback systems respond to a change _____
change that is about to happen and elicit a response before it happens.
•
Feedback systems require the change to be sensed and relayed back to a control center, prior to the reaction
or response
Positive feedback: accelerates a process by moving a variable further from a set point
_______
•
Example: Oxytocin during childbirth. Oxytocin is released during labor, which is sensed and stimulates
the posterior pituitary to release more oxytocin. Oxytocin evokes stronger muscle contractions to
push the child out the birth canal
Negative feedback: minimizes changes from the set point of a system, leading to stability
________
•
Example: Blood sugar regulation. If blood sugar is too low, glucagon is released from the pancreas to
stimulate the liver to release glucose into the blood. If blood sugar is too high, insulin is released to
stimulate an increase in glucose uptake by the tissues.
Feedf
orward regulation:
________
a change in a variable is anticipated, and a response is evoked to minimize
fluctuations in the variable
•
Example: Central command. At the onset of exercise, central command causes the parallel activation
of motor and cardiovascular control centers, such that heart rate will increase immediately at the
onset of exercise in anticipation of the increased metabolic demand of exercise
8
- sensor
- controlcenter
- effector
The variable returns to
normal
(negative feedback)
Feedback System
A variable
fluctuates from
the set point
- doesn'
tneed sensor
Change in a
variable is
anticipated
The change is
sensed and
relayed back to
appropriate
control centers
A response is
elicited
The variable is further
perturbed from baseline
(positive feedback)
Feedforward System
A response is
elicited
The variable fluctuates
from the set point, but to a
lesser degree due to the
response
*In some cases, homeostatic control systems include both feedforward and feedback mechanisms
*There are also cases where the set point of a variable may be temporarily reset, such as body temperature
during a fever, or blood pressure during exercise
9
General Principals of Physiology
1. Homeostasis is essential for health and survival – there is a necessity to maintain physiological
variables within normal ranges
•
Challenges to homeostasis may result from disease, or exposure to chronic/extreme stressors
2. Organ systems’ functions are coordinated with each other
•
Organ system do not function independently, but instead are highly integrative with one another
multiple
3. Most physiological functions are controlled by __________
regulatory systems, often working
in opposition
•
Feedforward and feedback control mechanisms
4. Information flow between cells/tissues/organs is an essential feature of homeostasis, and
allows for integration of physiological processes
controlled
5. Exchange of materials between compartments and across membranes occurs in a _________
manner
•
Compartmentalization is an important feature in physiology
6. Physiological processes are dictated by the laws of physics and chemistry
7. Physiological processes require the transfer and balance of matter and energy
8. Structure is a determinant of (and has coevolved with) function
10
The Hierarchy of Body Organization
Organizational Hierarchy:
cell
• Molecules, proteins, fats, and carbohydrates form together to make up a ___
tissue
• Multiple cells of the same type coordinate together to make up a ______
organ
• Two or more different types of tissues come together to make up an _____
organ system
• Multiple organs come together to make up an ____________
whole organism
• All organ systems of the body work in concert to comprise the ___________
Definitions (found in Ch 1.2):
• Cell: the simplest structural unit of life; retains the functions and characteristics of life
• Four main types of cells: muscle, neuron, connective, and epithelial
• Tissue: aggregates of differentiated cells with similar properties
• Organs: composed of two or more types of tissues
• Organ System: group of organs that work together to perform the same overall
function
Chat
11
Figure 1.1
The Hierarchy of Body Organization
Organizational Hierarchy:
• Molecules, proteins, fats, and carbohydrates form together to make up a ____
• Multiple cells of the same type coordinate together to make up a ______
• Two or more different types of tissues come together to make up an ______
• Multiple organs come together to make up an __________
• All organ systems of the body work in concert to comprise the _____________
Definitions (found in Ch 1.2):
• Cell: the simplest structural unit of life; retains the functions and characteristics of life
• Four main types of cells: muscle, neuron, connective, and epithelial
• Tissue: aggregates of differentiated cells with similar properties
• Organs: composed of two or more types of tissues
• Organ System: group of organs that work together to perform the same overall
function
While we often study organ system separately, they are actually quite interactive and
often we may require multi-organ system coordination for proper functioning
12
Figure 1.1
Types of Cells
contracti
l
e properties that allow them to produce and relay force
• Muscle cells: have intrinsic _________
•
Forms organs such as the heart, skeletal muscle, and sphincters of the stomach and bladder.
el
ectri
cal signals, to allow for conscious and
• Neurons: cells that initiate and conduct ________
subconscious control of the body
barri
ers to protect the body/organs
• Epithelial cells: forms _______
•
Selectively secretes/absorbs ions and organic molecules
•
Forms tissues that make up the skin, the lining of
the gastrointestinal tract, ducts and glands, etc.
support the
• Connective tissue cells: connect, anchor, and _______
structures of the body
•
Contributes to the formation of the extra-cellular
matrix (ECM)
13
Muscle Cells
All muscle cells
generate mechanical
force, however there
are distinct
differences between
the three types of
muscle cells
di
gest
Function
movesbl
ood through the
ci
rcul
atorysystem
movesand posi
ti
onsthe body
movesfl
ui
d and sol
i
dsthrough the GI
system, regul
atesarteri
aldi
ameter
Control
i
nvol
untary(autonomi
c)
vol
untary(somati
c)
i
nvol
untary(autonomi
c)
heart
muscl
esresponsi
bl
e forl
ocomoti
on,
breathi
ng, faci
alexpressi
on, and
posture
bl
ood vessel
s, tubesofthe GItract,
wal
l
sofsome organs
Location
Cellular
Differences
branchi
ng cel
l"chai
ns"that
are UNIorBInucl
eated, wi
th
stri
ati
ons
eated cel
l
swi
th NO stri
ati
ons
veryl
ong, cyl
i
ndri
cal
, MULTI-nucl
eated UNI-nucl
cel
l
swi
th stri
ati
ons
14
Neurons
electricalimpulses
excitable cells that have the ability to transmit _______
Neurons are _______
•
These electrical impulses serve as signals for neurons to communicate with other neurons or tissues
•
Neurons do not all look the same; they exist in a variety of
shapes and sizes within the body
•
All neurons function in allowing for cell-to-cell
communication
•
Excitable: a cell or tissue’s ability to respond to stimulation
functional unit of the nervous system
Neurons are the ________
Glial cells are non-neuronal cells that support neurons
• Note that glial cells are not neurons, and are instead a type of
connective tissue cell
• Glial cells do not have the ability to transmit electrical
impulses
The connection between a neuron and another cell is
synapse
called a _______
Figure 6.1
15
Neurons – Anatomy and Definitions
Definitions:
• Soma: the cell body of a neuron
• Dendrites: long projections extending from the soma
i
ncomi
ng information and relaying
• Function in receiving _________
it back to the soma
• Has dendritic spines that increase surface area
soma that relays
• Axon: A long process extending from the _____
outgoing signals to target cells
• Begins at the axon hillock and ends at the axon terminal
Myelin
• _______:
an insulating sheath that forms over some neurons,
that speeds up the transmission of an electrical signal down the
axon
• Made up of 20-200 layers of plasma membrane
INPUT
DENDRITES
SOMA
AXON
OUTPUT
Figure 6.1
16
Neurons – Myelin Sheath and Nodes of Ranvier
Two types of glial cells create the myelin
sheath:
•
Oligodendrocytes (CNS)
•
Schwann Cells (PNS)
The myelin sheath is not continuous
•
There are “gaps” in the sheath called the
Ranvi
er
Nodes of ______
•
These nodes speed up the transmission of
an electrical signal down the axon, and
also conserves energy
17
Figure 6.2
Epithelial Cells
Epithelial cells are cells that are specialized for specific functions: selective secretion, absorption of
ions/molecules, and protection
•
They are characterized and named according to their unique shapes and layers:
Naming by Shape:
•
Squamous – more flat/thin shape
•
cube shape
Cuboidal – ____
•
col
umn
Columnar – _______shape
•
Transitional – generally smaller than squamous
change shape
cells but may _____
Naming by Layers:
•
si
ngl
e cell layer
Simple – _____
•
1 cell layer
Stratified – more than ___
•
Pseudostratified – single cell layer, but some
cells may overlap others, giving the appearance
strati
fi
cati
on
of __________
18
Epithelial Cells
Epithelial cells are cells that are specialized for specific functions: selective secretion, absorption of
ions/molecules, and protection
•
They are characterized and named according to their unique shapes and layers:
Naming by Shape:
•
Squamous – more flat/thin shape
•
Cuboidal – cube shape
•
Columnar – column shape
•
Transitional – generally smaller than squamous
cells but may change shape
Naming by Layers:
•
Simple – single cell layer
•
Stratified – more than ____ cell layer
•
Pseudostratified – single cell layer, but some
cells may overlap others, giving the appearance
of ________
19
Epithelial Cells
Epithelial cells are found in tissues that cover the body or individual organs
•
Examples: skin, nails, lining of the trachea, lining of the GI tract, parts of the male and female
reproductive systems, parts of the urinary system, etc.
Generally, functions of epithelial tissues can be categorized as follows:
1.
protection from chemicals, climate/dehydration, abrasion or mechanical injury, or
Physical _________
biological agents
2.
permeability and maintain electrochemical gradients
To control ___________
•
Also, to transmit or monitor the absorption and release of nutrients, waste products, or
other chemicals and molecules
3.
sensation – Support sensory neurons located in the skin, nose, mouth, eyes, and ears
Enabling __________
4.
secretions
Produce specialized ___________
•
Some epithelial cells are also gland cells, meaning they may produce secretions
(examples: mucus, sweat, saliva, gastric enzymes, oil)
20
Epithelial Cells
Epithelial cells rest on a basement membrane
Each side of the epithelial cell can perform
separate functions
•
apicalside of the cell is
In this case, the _____
allowing for transport of glucose INTO the cell,
basolateral side of the cell is
while the __________
allowing for transport of glucose OUT of the
cell
Apical side: the side of the epithelial cell that
l
umen or external space
faces the _____
Basolateral (basal) side: the side of the epithelial
anchored to the basement membrane
cell that is _________
Basement membrane: an extracellular protein
layer that anchors the epithelial tissue
21
Connective Tissue Cells
Connective-tissue cells serve to connect, anchor, and support the structures of the body; main
functions:
•
Bind and support – ligaments, tendons, bones
•
Protect – bones and cartilage, adipose tissue, immune cells
______
•
Insulate – adipose tissue
•
Transport – blood
_________
There are many types of connective tissue cells, all of which serve a variety of functions. In
general, connective tissue consists of three primary constituents:
1.
Cells – e.g., Fibroblasts, Macrophages, Mast Cells, Plasma Cells, Adipocytes, Leukocytes
2.
Extracellular Matrix (ECM) – comprised of fibrous proteins such as collagen and elastin
3.
Tissue Fluid – comprised of ground substance, which is a clear, viscous fluid containing
proteoglycans
22
Types of Connective Tissue
There are six general categories of connective tissue:
1) Loose connective tissue
2) Dense connective tissue
3) Cartilage
4) Bone
5) Blood
6) Lymph
23
Pearson
Connective Tissue Proper
Loose Connective Tissue:
•
•
•
Areolar tissue is present between the skin and muscle
• Contains both collagen and elastin fibers •found in the loose
meshworkofcel
l
s and
• Edema: areolar tissue swells with fluid fibersunderlying
mostepi
thel
i
all
ayers.
Adipose tissue is present deep to the skin
i
nsul
ati
on energy storage, and
• Important for _______,
protection (cushion/padding)
Reticular tissue provides the supporting framework for
the kidneys, liver, spleen, lymph nodes, and bone marrow
Dense Connective Tissue – contains more closelypacked fibers than LCT:
• Dense regular CT is present in tendons, ligaments, and
the dermis of the skin
vascul
ari
zed
• Not well ________
• Dense irregular CT is found in the dermis of the skin
vascul
ari
zed
• Well _________
• Elastic CT is found in the walls of blood vessels, as well in
the ligaments between the vertebrae
Pearson
24
Fluid Connective Tissues
Blood:
• A type of fluid connective tissue that functions to transport
metabol
i
cwaste products
nutrients, gases, and _____________
• Composed of:
• Platelets, and red and white blood cells (45%)
pl
asma (55%)
• _______
• Moves through blood vessels
• Arteries, arterioles, capillaries, venules, veins
Lymph:
drai
n excess
• A type of fluid connective tissue that functions to ___________
tissue fluid
• Composed of:
i
ntersti
ti
al fluid)
• Lymph fluid (_________
• White blood cells
• Ions, organic molecules, cellular debris, proteins, etc.
• Moves through lymphatic vessels
Pearson
25
Supporting Connective Tissues
Cartilage:
col
l
agen to form a
• Chondrocytes: mature cartilage cells that produce ________
cartilage matrix
avascul
ar
• Is _________,
and thus has a relatively longer healing time after injury
• Primarily functions to support other structures
•
•
•
Hyaline cartilage: Present at the end of long bones, between the ribs and
sternum, the trachea, larynx, and bronchi
Elastic cartilage: Present in the external ear and larynx
Fibrous cartilage: Present in intervertebral disks, pubic symphysis, and in the
knee joint
Bone:
crystal
l
i
ne
• Bone tissue is a solid, _________
matrix made from calcium
salts and collagen fibers
•
•
•
Pearson
~2% bone cells
~65% matrix
~33% collagen fibers
• Is very well-vascularized
26
Figure 11.30
Organ Systems
27
The Skeletal System
The skeletal system refers to the bones of the body, but also the cartilages,
ligaments, and connective tissues that stabilize and inter-connect the bones.
Five primary functions:
Structural support – provides a framework for tissues and organs to attach to
1. ________
softorgans and _____________
delicate tissues
2. Protection of _______
•
E.g., ribs protect the heart and lungs from physical trauma
minerals
3. Storage of ________
•
Primarily Calcium (Ca2+) and Phosphate ions (PO43-)
4. Blood cell production
•
pl
atel
ets are produced in red bone marrow
Red and white blood cells, and ________
•
Red bone marrow fills the cavities of many bones
5. Leverage
•
muscl
es can act upon to generate force
Provides a lever on which ________
29
Bone Anatomy Review
The epiphysis is an
expanded area found at
each end of a long bone
Spongy bone
Articular cartilage
Epiphysis
Bone exists in two layers:
• Spongy bone: consists of a
branching, open network of
struts and plates that
l
atti
cework
resembles ________
• aka trabecular or
cancellous bone
The metaphysis is the Metaphysis
narrow zone connecting
the epiphysis to the shaft
of a long bone
The diaphysis is the long
and tubular shaft of a long
bone
Compact bone
Diaphysis
• Compact bone: thin, dense
layer of bone that surrounds
spongy bone
corti
cal bone
• Aka _______
Partially sectioned tibia (shin bone)
30
Bone Anatomy
Spongy bone
Articular cartilage
Epiphysis
Medullary or marrow
cavity
Periosteum
____________
is a connective
tissue that wraps around the
diaphysis
fibrous outer
• Has two layers: a ______
cellular inner layer
layer and a _______
• Fibrous layer contains Sharpey’s
fibers
• Cellular layer contains
fibroblasts, osteogenic cells,
and osteoblasts
Compact bone
•
Epiphyseal artery
Epiphyseal vein
Epiphyseal growth plate (or
epiphyseal line)
Metaphysis
Metaphyseal artery
Metaphyseal vein
Diaphysis
Periosteal artery
Periosteal vein
Periosteum
Nutrient foramen
Nutrient vein
Partially sectioned tibia (shin bone)
Nutrient artery
•
Contains an extensive network
of blood vessels, lymphatic
vessels, and sensory nerves
Allows for nerves and blood to
pass through to the bone, and
tendon and
also allows for _______
l
i
gament
__________
attachment
31
Short, Flat, and Irregular Bone
Fibrous outer
layer
Cellular inner
layer
Periosteum
Compact bone tissue
Spongy bone tissue
Compact bone tissue
https://open.oregonstate.education/aandp/chapter/6-3-bone-structure/
32
Bone Anatomy
Spongy bone
osseous tissue
Bone is also known as ________
vascul
ari
zed
• Take note of how highly __________
osseous tissue is
• Bones require an extensive blood
supply to grow and be maintained
Articular cartilage
Epiphysis
Epiphyseal artery
Epiphyseal vein
Epiphyseal growth plate
(or epiphyseal line)
Metaphysis
Metaphyseal artery
Metaphyseal vein
A
Medullary or marrow
cavity
A
The endosteum is an incomplete
cell layer that lines the medullary
cavity
• ALSO covers spongey bone
and lines the central canals
Compact bone
Diaphysis
Periosteal artery
Periosteal vein
Periosteum
Nutrient foramen
Nutrient vein
Partially sectioned tibia (shin bone)
Nutrient artery
The nutrient foramen is a tunnel that
penetrates the diaphysis and provides
access for the nutrient artery and vein
• Usually bones only have one nutrient
artery and vein
33
The Osteon is the Structural Unit of Compact Bone
Diaphysis Partial Cross-Section
34
The Osteon
l
i
ke bl
ood vessel
s
Canaliculi are narrow
passageways extending
from the lacuna into the
lamellae.
Osteocytes account for most of the cell population in bone
Each osteocyte cell occupies a lacuna, which is a pocket sandwiched
between layers of matrix
osteocyte
l
acuna will only ever contain one _________
One ______
Lacunae is not the same as lamellae
• Lamellae: thin layers of matrix
• Lacunae: a pocket within the matrix that contains an osteocyte
https://open.oregonstate.education/aandp/chapter/6-3-bone-structure/
Canaliculi are important
erconnectingall the
in int
__________
vascular
lacunae to _________
passageways, allowing
the osteocytes to receive
nutrients and dispose of
waste products
35
Bone Cell Types
Osseous tissue is a type of connective tissue that consists of cells at various stages of the life cycle
progenitor
Osteo__________
(Osteogenic) cell
blast
Osteo_____
cyte
Osteo____
clast
Osteo_____
*deri
vesfrom di
fferent
stem cel
l
Ruffled
border
• A type of stem cell • A premature bone
cell in the
that resides within
periosteum
bone
bui
l
ders
• Bone ________
• Has the ability to
• Secrete collagen
divide into
osteobl
asts
and chrondroitin
_____________
into the matrix of
• Play a major role in
bone
healing fractures
• Mature bone cells
present in the lacunae
• Important in bone
turnover
________
and repair
• Occasionally referred
to as osteoblasts that
are “trapped” within
the matrix of the bone
• A type of bone cell that
originates from hematopoietic
progenitor cells
• Resides on the surface of
bone
nucl
eated
• Multi-_____________
• Functions in bone resorption;
the breakdown of bone matrix 36
Osseous Cell Types within the Osteon
Where are the osteoprogenitor cells?
https://open.oregonstate.education/aandp/chapter/6-3-bone-structure/
Osteon Cross-Section
Figure 11.30
37
Bone Cell Types
The process of producing
new bone matrix is known as
ossification
___________
or osteogenesis
• Occurs normally
throughout the lifespan,
but increases during
periods of growth (fetal
development and
childhood) and post-injury
The process of dissolving the
bone matrix is known as
osteolysis or bone
_________
resorption.
• Osteolysis occurs normally
throughout the lifespan
• Is important in regulating
calcium and phosphate ion
concentrations in the body
38
https://open.oregonstate.education/aandp/chapter/6-3-bone-structure/
Osteogenesis (Bone Development)
Osteogenesis occurs throughout the lifespan
• Occurs during embryonic development in the form of new bone formation
• Occurs during childhood and adolescence during normal childhood development and puberty
• Occurs during adulthood in the form of bone remodeling
repl
acement tissue
Bone can be considered a ___________
• For bone to develop, it requires a model tissue to use as a template
Two types of ossification:
mesenchymal cells directly into bone cells
Intramembranous ossification: the differentiation of ____________
•
Mesenchymal cells are used as the model framework
•
Responsible for the development of bones of the skull, the mandible, the clavicle and sesamoid bones
knee cap/patel
l
a
hyal
i
ne carti
l
age
Endochondral ossification: the formation of bone cells in place of ________________
cells
•
The cartilage cells do not become bone cells, but are instead used as a TEMPLATE for bone cells to form
•
Responsible for the development of most bones, except for the bones listed above
https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_1e_(OpenStax)/Unit_2%3A_Support_and_Movement/06%3A_Bone_Tissue_and_the_Skeletal_System/6.04%3A_Bone_Formation_and_Development
39
Osteogenesis - Intramembranous Ossification
Intramembranous ossification: the differentiation of mesenchymal cells directly into bone cells
Intramembranous ossification begins
during embryonic development
a) Mesenchymal cells begin to cluster
osteoi
d (collagen
and secrete ________
matrix), which crystallizes
•
This becomes the ossification center
b) As the matrix further ossifies, some
osteoblasts become trapped inside
bony pockets, and differentiate into
osteocytes
c) Formation of trabeculae and
periosteum, and introduction of
vascul
ari
zati
on – necessary to keep
____________
the osteocytes viable
d) Compact bone develops superficial to
the spongy bone, and some blood
vessels crowd together to form red
40
bone marrow
https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_1e_(OpenStax)/Unit_2%3A_Support_and_Movement/06%3A_Bone_Tissue_and_the_Skeletal_System/6.04%3A_Bone_Formation_and_Development
Osteogenesis – Endochondral Ossification
Cartilage is an avascular tissue, and thus takes
relatively longer to heal than other tissues.
Endochondral ossification: the formation of bone cells in place of hyaline cartilage cells
Mesenchymalcel
l
sform a hyal
i
ne carti
l
age model
.
- chondrocytes nearthe centre i
ncrease i
n si
ze and di
e,
l
eavi
ng cavi
ti
esthatare l
aterfi
l
l
ed wi
th cal
ci
fi
ed matri
x.
- the centerwi
th
41
https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_1e_(OpenStax)/Unit_2%3A_Support_and_Movement/06%3A_Bone_Tissue_and_the_Skeletal_System/6.04%3A_Bone_Formation_and_Development
Bone Growth and Remodelling – Definitions
remodeling
Bone _________:
process in which the matrix of a bone is resorbed (dissolved) and replaced by new
bone by osteoblasts
•
Occurs normally, throughout the lifespan but increases post-injury or following periods of increased
mechanical stress or load (i.e., exercise)
l
ength that occurs in the lacunae
Interstitial growth: growth in bone _____
wi
dth (or thickness) that occurs due to new bone tissue being
Appositional growth: growth in bone _____
deposited on the periosteum, and resorbed from the endosteum
•
matri
x to the surface
Osteogenic cells differentiate into osteoblasts and deposit _____
Ossification: the laying down of new bone material (including osteocytes and calcium salts + osteoid)
Calcification: the formation of calcium salts & crystals within tissue.
•
Calcification is a step within the Ossification process (but not vice versa).
embryonic
The majority of bone development occurs during __________
development
•
•
During childhood, some cartilage will still be replaced with bone, but the predominant form of bone
development is interstitial and appositional growth
In adulthood, some cartilage remains but only bone remodeling will occur
42
Epiphyseal side
Interstitial Growth
Interstitial growth occurs at the epiphyseal plate in long bones
carti
l
age cel
l
s, ECM
Reserve Zone
• Contains small chrondrocytes that secure the epiphyseal plate
to overlying osseous tissue in the epiphysis
• Do not actively participate in bone growth
Proliferative Zone
l
arger chondrocytes that create new
• Contains slightly ______
chondrocytes to replace old/dead cells
Hypertrophic Zone
• Contains older/larger chondrocytes
growth
Calcification Zone
di
si
ntegrate
• Old chondrocytes die and _________
Ossification Zone
• Osteoblasts lay down new bone
43
https://open.oregonstate.education/aandp/chapter/6-4-bone-formation-and-development/
Diaphyseal side
Epiphyseal side
Interstitial Growth
Diaphyseal side
Developing bone of
diaphysis
Zone of calcified cartilage
Zone of hypertrophic
cartilage
Zone of proliferating
cartilage
(b) Histology of the
epiphyseal plate
Epiphyseal side
Zone of resting cartilage
LM400x
** upside down compared to diagram**
https://open.oregonstate.education/aandp/chapter/6-4-bone-formation-and-development/
44
Diaphyseal side
Bone Formation Concept Map
Endochondral Ossification
Intramembranous ossi
fi
cati
on
starts in
starts in
hyal
i
ne carti
l
age
Osteoblasts within connective tissue
secrete
produce
covered by
mature into
Perichondrium
becomes
col
l
agen
osteocytes
Trabeculae
osteobl
asts
forms
grow into
Spongy Bone
surrounded by
Organic Matrix /
Ground Substance
produces
occupy
in
Osteoblasts
l
acunae
in
in
develop into
Spongy Bone
surrounded by
compactbone
45
Supplementary Videos
Osteogenesis (summary video):
https://www.youtube.com/watch?v=z0ubmKapIoY
Endochronal ossification video:
https://www.youtube.com/watch?v=eBeyApWuGEI
Intramembranous ossification video (start @ 3:20)
https://www.youtube.com/watch?v=MZGRiUdg0RA
46
Bone: A Reservoir for Ca2+
99
Bone serves as a mineral reservoir, containing over __%
of the body’s total calcium
99
80
stores, __%
of the body’s phosphate stores, and __%
of the body’s carbonate
• Bone contains ions in the form of hydroxyapatite
Hydroxyapatite: an inorganic mineral consisting of crystals of calcium (Ca2+), phosphate (PO43+),
and hydroxyl/hydroxide (OH-) ions
By weight, ~1/3rd of bone is osteoid
and ~2/3rd is hydroxyapatite
The role of bone as a reservoir for calcium is
particularly important, because calcium plays
neurological function
a crucial role in normal _________
and muscular activity
47
Bone: A Reservoir for Ca2+
This is why bone remodeling occurs through adulthood
regulation of Plasma [Ca2+]
Bone remodeling allows for the _________
•
Plasma [Ca2+] that is too low or too high may result in various pathological conditions, like cardiac
arrhythmia
high hormones will be released
If plasma [Ca2+] is too ____,
osteoblast activity
to stimulate _________
•
Increase bone formation
•
Ca2+ from the plasma stored in bone
low hormones will be released
If plasma [Ca2+] is too ___,
osteoclast activity
to stimulate __________
•
Increased bone resorption
•
Ca2+ is released from the bone into the plasma
48
Bone: A Reservoir for Ca2+
Application Scenario:
The body senses that plasma [Ca2+] is too low. Homeostatic control systems interpret that signal and
generate a response to reduce bone formation, increase bone resorption, and increase Plasma [Ca2+]. Which
of the following responses would occur?
a)
Insulin is released
b) Parathyroid hormone is released
c)
Osteoclasts will resorb bone and dissolve calcium crystals
d) Osteoblasts will lay down new matrix to become mineralized
*Note: While all the hormones listed in this table influence bone mass,
only parathyroid hormone responds to plasma Ca2+ as a feedback signal
49
Ca2+: Other Homeostatic Control Mechanisms
Figure 14.6
The Kidneys:
•
Ca2+ is normally excreted into the tubules of the kidney, and then
reabsorbed into the blood
•
The amount of Ca2+ reabsorbed into the blood can be regulated to
minimize or maximize the amount of Ca2+ excreted in the urine
•
Decreased reabsorption → decreased plasma [Ca2+]
The Gastro-Intestinal Tract:
•
Not all the Ca2+ ingested is absorbed by the GI tract
•
Ca2+ absorption by the GI tract is under hormonal control
50
Figure 15.1
Clinical Application: Paget’s Disease
Paget’s disease is a condition in which
overacti
ve
osteoclasts are __________,
resulting in a
greater rate of bone resorption
• The osteoblasts try to increase their activity and
lay down new bone, however they cannot keep up
with the osteoclasts
• Over time, this results in bones that are weak,
fracture
brittle, misshapen, and prone to _______
• The cause of Paget’s disease is unknown, but
some research suggests it may be genetic,
environmental, and/or associated with aging
• Treatment: drugs that decrease the activity of
osteoclasts (such as bisphosphonates), and
surgery in some cases
51
https://open.oregonstate.education/aandp/chapter/6-3-bone-structure/
52