Download Bone - Canvas

Exam #1 wrap-up
Scores on Exam #1, 10-15-14
Answer key and scores
are posted to Canvas.
# of students
12
10
8
6
4
2
0
<70
70-79
80-89
90-100
The 2 questions for which scores were the lowest:
In which kind of connective tissue can you normally see a mix of cells that do and do
not have nuclei?
a. Connective tissue proper
b. Fluid connective tissue YES
c. Hyaline cartilage
d. Supporting connective tissue
Which kind of connective tissue is a major component of the walls of large arteries?
a. dense irregular b. dense regular c. elastic d. smooth muscle
YES
Remember:
BIOL 241
covers these
1st 4 organ
systems.
Integumentary:
Ch. 5.
Skeletal:
Ch. 6-9.
Muscular:
Ch. 10-11.
Nervous:
Ch. 12-16.
(Spotlight Figure 1-1)
Chapter 6
Osseous Tissue and
Bone Structure
Lecture Presentation by
Lee Ann Frederick
University of Texas at Arlington
(heavily modified by GJC)
© 2015 Pearson Education, Inc.
An Introduction to the Skeletal System
• The Skeletal System
• What does it include?
bones of the skeleton;
cartilages, ligaments, and other connective tissues.
Our main focus: bones!
© 2015 Pearson Education, Inc.
6-1 Functions of the Skeletal System
• Five Primary Functions of the Skeletal System
* Support
* Storage of Minerals (calcium) and Lipids (yellow marrow)
* Blood Cell Production (red marrow)
* Protection
* Levers for muscles (allow movement)
[Cartilage : protects adjacent bones]
© 2015 Pearson Education, Inc.
Bone Shapes
What do you normally picture when you think of a bone?
The kind a dog chews on?
This is a “long bone,” one of four basic bone shapes.
The others are: short, flat, and irregular.
(Lab manual considers sesamoid and sutural to be
examples of irregular bones, so we will follow that
system as well.)
Bone Shapes: Long vs. Flat
Spongy
bone
Epiphysis
Metaphysis
Note: both types have spongy and
compact bone, but in different places!
Language notes: epi = outer, meta =
middle, medulla = middle/center
Compact
bone
Diaphysis
(shaft)
Medullary
cavity
Metaphysis
Epiphysis
Compact bone
(Cortex)
Spongy bone
(Diploë)
Metaphysis – where bones grow!
(Details to come…)
Figure 6-3 Bone Structure.
Tricky bones, example 1: wrist/hand
Finger bones –
metacarpals and
phalanges – aren’t really
that long, but have the
basic shape of “Long”
bones and are classified as
long. It’s the carpals that
are classified as short
bones.
Short bones have a
different, “box-like” shape.
Figure 6-1c
Tricky bones, example 2: parietal bone; ribs
Both of these are
considered FLAT bones.
Bone Markings – see Table 8.1 of lab manual
Projections/Processes/Elevations
vs. Depressions/Openings/Tunnels
1.
You don’t need to memorize
these general terms, but be
aware and use as a guide
when looking at specific
bones.
Projections for tendon or ligament attachment:
crest, epicondyle, line, process, spine, trochanter tubercle, tuberosity
2.
Projections for forming joints:
condyle, facet, head, ramus
3.
Depressions/openings for blood vessels/nerves:
fissure, foramen, groove, notch
4.
Other depressions/openings:
fossa, meatus, sinus
Variations in bone shapes and markings offer clues about a person’s life! (next slide)
Anthropologists & pathologists analyze bones
http://anthropology.si.edu/writteninbone/
LEFT: Burned
body found in fire.
RIGHT: Part of
baby skull, 17thcentury Maryland.
LEFT: Was the fire the cause of death? Orange marks show broken ribs…. No signs of
healing….. Wounds were made by long knife, so building was torched to hide a murder!
RIGHT: baby with holes in skull. Any idea what happened here? Inadequate nutrition.
Answer key and scores
are posted to Canvas.
Number of students
Lab Quiz #1 wrap-up
Scores on Lab Quiz #1 (out of
75)
10
8
6
4
2
0
51-57
60-66
69-75
Bone (Osseous) Tissue: semi-review
Cells:
(b) and (c) are COMPACT BONE
Extracellular Matrix:
vein
nerve
artery
Canaliculus (i)
Lacuna (ae)
with
osteocytes
Lamella (ae)
Central canal
(contains nerves,
blood vessels)
Trabeculae of
spongy bone
lab manual, Figure 8.4; textbook, Figure 6-7
All of these
concentric circles
= 1 osteon
Structure of a Long Bone
• Diaphysis (dye-AFF-ih-sis)
• The shaft
• A heavy wall of compact bone, or dense bone
• A central space called medullary cavity
• Epiphysis (ee-PIFF-ih-sis)
• Wide part at each end
• Articulation with other bones (connections/joints)
• Mostly spongy bone
• Covered with compact bone (cortex)
Cortex = “outside” vs. Medulla = “middle”
© 2015 Pearson Education, Inc.
Figure 6-3 Bone Structure.
To which forces are long bones most
vulnerable?
Most vulnerable to
“sideways” forces
e.g., side tackle in
football
How do bones develop and mature?
• “Endochondral Ossification” (for long bones,
etc. - “inside cartilage turning to bone”)
• Ossifies bones that originate as hyaline cartilage
• Most bones originate as hyaline cartilage
• There are several steps in endochondral
ossification (next slides)
© 2015 Pearson Education, Inc.
Figure 6-11 Endochondral Ossification
1
1
Fetal bone:
Hyaline
cartilage,
chondrocyte
s in middle
© 2015 Pearson Education, Inc.
2
Invasion of
blood
vessels;
bring
fibroblasts
to become
osteoblasts.
3
4
Hollowing out of center of
bone (medulla); chondrocytes
are dying off and migrating
toward epiphyses.
Figure 6-11 Endochondral Ossification (continued)
5
Hyaline cartilage on end
7
6
5
Epiphyses: spongy
bone replaces
hyaline cartilage.
Blood vessels
into epiphyses;
spongy bone
starts forming
there as well.
© 2015 Pearson Education, Inc.
Post-puberty:
epiphyseal plate
(cartilage replaced
with spongy bone)
Lab manual
figure: 8.5:
Sequential migration
of chondrocytes and
osteocytes
Bone Formation and Growth
• Epiphyseal Cartilage (in diaphysis, migrating
toward epiphysis)
• When long bone stops growing, after puberty:
• What happens to epiphyseal cartilage?
• Converted to bone (by trailing osteocytes)
• What’s visible on x-rays? (see next slide)
© 2015 Pearson Education, Inc.
Figure 6-10 Bone Growth at an Epiphyseal Cartilage.
Post-puberty: epiphyseal
cartilage (in metaphysis) has
disappeared, leaving only
thin epiphyseal plate (not
visible here)
© 2015 Pearson Education, Inc.
End-of-chapter review question #29
Frank does not begin puberty until he is 16. What effect
would you predict this will have on his stature?
(a) Frank will probably be taller than if he had started
puberty earlier – YES! (more time til end of puberty
stops bone growth)
(b) Frank will probably be shorter than if he had started
puberty earlier
(c) Frank will probably be a dwarf
(d) Frank will have bones that are heavier than normal
(e) The late onset of puberty will have no effect on
Frank’s stature
© 2015 Pearson Education, Inc.
Bone Remodeling
• Process of Remodeling
• The adult skeleton:
• Replaces mineral reserves
• Recycles and renews bone matrix
• Involves 3 cell types:
• Osteoclasts: “tear up” bone tissue
• Osteoblasts: build up bone tissue
• Osteocytes: “mature” bone cells in lacunae, which
maintain matrix
© 2015 Pearson Education, Inc.
Bone Remodeling
Shin & Cho, Journal of Korean Society of Endocrinology 2005
Both happen simultaneously!!!
Bone Remodeling
• Process of Remodeling
• Bone continually remodels, recycles, and replaces
• What happens if deposition (by osteoblasts) is
greater than removal?
• Bones get bigger, stronger – sometimes TOO big
(bone spur)
• What happens if removal is faster than
replacement?
• Bones get thinner, weaker
Exercise: weight-bearing exercise (support body weight),
weight-lifting stimulates thickening of bones
© 2015 Pearson Education, Inc.
Bone remodeling & exercise: “Use it or lose it!”
• Bed rest or “couch potato” behavior
• Exercise (are all forms equally good?)
J.F. Nichols et al., Osteoporosis
International 2003
Old cyclists: lots of lowimpact exercise does not
protect bones from thinning!
Advice: mix it up, do some
running/weight lifting!
+ NUTRITION (Ca,
Phosphorus, D3 intake)
(old)
What would you recommend to maintain
optimal bone density?
(see previous slide)
Variety: reach different bones and
different muscles with different
exercises!
Bones, Hormones, and Nutrition
• Normal Bone Growth and Maintenance Depend
on Nutritional and Hormonal Factors
• The hormone calcitriol
• Made where? Kidney!
• Helps digestive tract absorb what?
•
calcium
• Synthesis requires what precursor?
• Cholecalciferol (made in skin)
• Liver continues conversion process
© 2015 Pearson Education, Inc.
Bones & Hormones
• Osteoblast activity and synthesis of bone matrix is
stimulated by hormones like growth hormone and
estrogens/androgens.
• Implications for anorexic teenagers?
• Not enough nutrients, not growing bones well…
Very hard to build this bone later (as an adult)!
• Implications for older folks?
• Less exercise … estrogen goes way down in postmenopausal women… (estrogen can be an issue
in anorexic women as well!)
6-8 Calcium Homeostasis
• The Skeleton as a Calcium Reserve
• Bones store calcium and other minerals
• Calcium ions are vital to:
• Neurons
• ions involved in electrical signaling; calcium
specifically triggers neurotransmitter release
at axon terminus
• Muscle cells, especially heart cells
• Calcium stimulates actin and myosin to
interact => contract
© 2015 Pearson Education, Inc.
Calcium Homeostasis
• Calcium ions in body fluids must be closely regulated
• Homeostasis is maintained by 2 (or 3) hormones:
calcitriol
PTH = parathyroid hormone
calcitonin
* Intestinal absorption
* Osteoclast activity increases blood calcium levels;
Osteoblast activity decreases blood calcium levels
* Kidney can retain calcium (or let it leave in urine)
© 2015 Pearson Education, Inc.
Figure 6-15a Factors That Alter the Concentration of Calcium Ions in Blood.
a
Factors That Increase Blood Calcium Levels
Low Calcium Ion Levels in Blood
(below 8.5 mg/dL)
Parathyroid Gland Response
Low calcium levels cause the
parathyroid glands to secrete
parathyroid hormone (PTH).
PTH
Bone Response
Osteoclasts stimulated to
release stored calcium ions
from bone
Intestinal Response
Rate of
intestinal
absorption
of calcium
increases
Kidney Response
Kidneys retain
calcium ions
more
calcitriol
Calcium released Calcium absorbed quickly
Ca2+
levels in
blood
increase
© 2015 Pearson Education, Inc.
Calcium conserved
Decreased calcium
loss in urine
Figure 6-15b Factors That Alter the Concentration of Calcium Ions in Blood.
b
Factors That Decrease Blood Calcium Levels
High Calcium Ion Levels in Blood
(above 11 mg/dL)
Thyroid Gland Response
Parafollicular cells (C cells) in the
thyroid gland secrete calcitonin.
Calcitonin
Bone Response
Intestinal Response
Osteoclasts inhibited while
osteoblasts continue to lock
calcium ions in bone matrix
Rate of
intestinal
absorption
of calcium
decreases
Kidney Response
Kidneys
allow
calcium
loss
less
calcitriol
Calcium absorbed slowly Calcium excreted
Calcium stored
Ca2+
levels in
blood
decrease
© 2015 Pearson Education, Inc.
Increased calcium
loss in urine
Figure 6-15 set to music (revised)
When blood calcium is HIGH,
The thyroid sends out calcitonin;
When blood calcium is LOW,
The parathyroid gland gets goin’.
When blood calcium is HIGH,
There’s less intestinal absorption;
When blood calcium is LOW,
The kidney saves a greater portion.
Figure 6-15 set to music (revised)
Melody playback:
http://www.noteflight.com/scores/view/0cbd7455cee28fb56162b76aef5256602dd2c6ee
Summary of homeostasis in preceding figure
• Regulated variable?
• Blood calcium levels
• Setpoint?
• 8.5 to 11 mg/dL is apparently optimal
• Effectors?
• For high calcium: Thyroid? Calcitonin? Kidney,
intestine, osteoclasts/blasts? (all of above)
© 2015 Pearson Education, Inc.
Fractures
• Fractures
• Cracks or breaks in bones
• Caused by physical stress
• Fractures are repaired in four steps
1. Bleeding
2. Cells of the endosteum and periosteum
1. Endosteum = “inner cells” at edge of medulla
2. Periosteum = cells on outside
3. Osteoblasts
4. Osteoblasts and osteocytes remodel the fracture for
up to a year
© 2015 Pearson Education, Inc.
Figure 6-16 Types of Fractures and Steps in Repair.
Spongy bone of
internal callus
Cartilage of
external callus
Fracture
hematoma
External
callus
Dead bone
Bone fragments
1 Fracture hematoma
formation.
Spongy bone of
external callus
Periosteum
Internal callus
2 Callus formation.
External callus
3 Spongy bone formation.
4 Compact bone
formation.
Compare & contrast with inflammation!
Inflammation
Bone Fracture
“First responder” cells Mast cells (release
histamine)
No great equivalent…
Initial response
Clot/scab with fibrin protein
Clot/scab with fibrin protein
Later rebuilding
Collagen, mostly
Cartilage & spongy bone
“Good as new”?
Not really – scar tissue
Can be – extra-strong, but
callus may intrude at joints
© 2015 Pearson Education, Inc.
Textbook
Topic
Lab Manual
Chapter 7
The Axial
Skeleton
Exercise 9
Chapter 8
The Appendicular
Exercise 10
Skeleton
For these chapters we will not use the textbook, except as a backup resource.
© 2015 Pearson Education, Inc.