bioh111 sn09 skeletal system · edition: chapter 6 © endeavour college of natural health...

© Endeavour College of Natural Health endeavour.edu.au 1

BIOH111

oCell Module

oTissue Module

o Integumentary system

oSkeletal system

oMuscle system

oNervous system

oEndocrine system


TEXTBOOK AND

REQUIRED/RECOMMENDED READINGS

o Principles of anatomy and physiology. Tortora et al; 14th

edition: Chapter 6


BIOH111 – SKELETAL SYSTEM MODULE

o Session 9 (Lectures 13 and 14) – Bone physiology:

Building of bone organ – cells, tissue, organ and

repair

o Session 10 (Lectures 15 and 16) - The Skeletal

System: Axial and Appendicular Skeleton, Joints

and Movement


PREPARATION FOR THIS SESSION

o NO MISSING CONCEPTS OR LINKING WORDS from

Session 6

o Review:

• receptors

• homeostasis

• tissue types

o Think about cells as immature and specialised (mature)

– why is there a difference?

BIOH111

Lectures 13 and 14

Bone physiology: Building of bone organ –

cells, tissue, organ, development and repair

Department of Bioscience

endeavour.edu.au


OBJECTIVESLecture 13:

Identify and describe function of the overall skeletal system

Bone cells and tissue

Name and describe bone cells and their function in building and function

of bone tissue

Describe structure and function of 2 bone tissue types – compact and

spongy

Long bone as an example of bone organ

Describe structure and function of long bone sections

Lecture 14:

Development and growth of bone tissue

Recognise 2 types of bone development (ossification)

Describe process of growth (length and thickness)

Identify steps in bone remodelling and fracture repair


SKELETAL SYSTEM FUNCTION 1. Support – structural framework for the body

2. Protection – protects internal organs from injury

3. Assistance in movement – muscles involved in movement

attached to the skeleton

4. Mineral homeostasis – major calcium and phosphorus

reservoir

5. Blood cell production – stem cells for production of WBCs

and RBCs (red bone marrow)

6. Triglyceride storage – adipose tissue; energy reserve


BONE STRUCTURE

o Bone is made up of several different tissues:

bone, cartilage, dense connective tissue, epithelium, various blood

forming tissues, adipose tissue and nervous tissue

o 1 bone = 1 organ

o bones + cartilage +ligaments + tendons = skeletal system

o Bone constantly undergoes remodeling

o NOTE: ‘bone’ means both the tissue and the structural unit

of a skeleton

Building bones: cells → tissue → organ


BONE CELLS

o Osteogenic cells – undifferentiated, stem cells

• can divide to replace themselves & can become osteoblasts

• found in inner layer of bones

o Osteoblasts - form matrix & collagen fibers but can’t divide

o Osteocytes - mature cells that no longer secrete matrix and are the principle cells of bone matrix

o Osteoclasts - huge cells from fused monocytes (WBC)

• function in bone resorption

cells → tissue → organ


CELLS OF

BONE Osteoblasts Osteocytes Osteoclasts


BONE (OSSEOUS) TISSUE – revision

o Type of connective tissue as seen by widely spaced bone

cells separated by matrix.

• Matrix - 25% water, 25% collagen fibers & 50% crystallized mineral

salts (hydroxyapatite and some calcium carbonate)

o Calcification or mineralization – process of mineral salts

deposition in a framework of collagen fibers

• Mineral salts confer hardness on bone while collagen fibers give

bone its great tensile strength

o Bone is not completely solid - small spaces for vessels and

red bone marrow

o 2 types: compact and spongy bone



COMPACT BONE

Structure: solid, hard layer of bone; makes up the shaft of long bones and the external layer of all bones

Function: resists stresses produced by weight and movement


COMPACT BONE HISTOLOGY

o Arranged in units called osteons or Haversian systems.

• Osteons contain blood vessels, lymphatic vessels, nerves, osteocytes

and calcified matrix

o Osteons are aligned in the same direction along lines of stress.


SPONGY BONE

Structure: light of bone; found only on the interior of the bones; most of the structure of short, flat, and irregular bones (e.g. ribs), and the ends of the long bones

Function: supports and protects the red bone marrow


o Arranged in trabeculae (latticework of thin plates of bone) that

surround many red marrow filled spaces

o Trabeculae are irregularly arranged.

SPONGY BONE HISTOLOGY


TYPES OF BONES

o 5 basic types of bones classified

by shape:

• Long - compact

• Short - spongy except surface

• Flat - plates of compact

enclosing spongy

• Irregular - variable

• Sesamoid - develop in tendons

or ligaments (patella)

o Sutural bones – classified by

location; in sutures (joints)

between skull bones



o Diaphysis:

• “growing between”; shaft – long

cylindrical main portion of the bone

o Epiphyses:

• “growing over”; ends of the bone;

distal or proximal

o Metaphyses:

• joins diaphysis and epiphyses;

• epiphyseal plate (<20yo; cartilage)

→ epiphyseal line (>20yo; bone)

Why the bold letters?

LONG BONE STRUCTURE



o Articular cartilage:

• hyaline cartilage covering the part of

epiphysis where the bone forms a joint;

reduces friction

o Medullary cavity:

• marrow cavity within the diaphysis;

contains bone marrow

o Endosteum:

• membrane that lines the medullary

cavity; single layer of bone forming cells

and connective tissue

o Periosteum:

• tough sheath of dense irregular

connective tissue that surrounds the

bone surface

o Nutrient foramen:

• entry point for blood vessels


BLOOD SUPPLY OF BONE

o Periosteal arteries• supply periosteum

o Nutrient arteries• enter through nutrient foramen

• supplies compact bone of diaphysis & red marrow

o Metaphyseal & epiphyseal arteries• supply red marrow & bone

tissue of epiphyses

For interest only


Structure Function

Diaphysis

Epiphyses

Metaphyses

Articular cartilage

Medullary cavity

Endosteum

Periosteum

REVISION LONG BONE


OBJECTIVESLecture 13:

Bone cells and tissue

Name and describe bone cells and their function in building and function

of bone tissue

Describe structure and function of 2 bone tissue types – compact and

spongy

Long bone as an example of bone organ

Describe structure and function of long bone sections

Lecture 14:

Development and growth of bone tissue

Recognise 2 types of bone development (ossification)

Describe process of growth (length and thickness)

Identify steps in bone remodelling and fracture repair


BONE FORMATION AND GROWTH

Bone formation is termed osteogenesis or ossification and

occurs in 4 situations: fetal bone formation, childhood bone growth,

bone remodeling and fracture repair.

o Two types of ossification occur:

1. Intramembranous ossification – bone forms directly from

or within fibrous connective tissue.

2. Endochondral ossification – bone forms from hyaline

cartilage.

o Two types of bone growth occur:

1. Growth in length

2. Growth in thickness


GROWTH IN LENGTH

At birth only Articular cartilage and Epiphyseal plate have not

been converted to bone – sites of the bone growth in length.


GROWTH IN LENGTH –

e.g. EPIPHYSEAL PLATE o Growth stages:

• cartilage cells are

produced by mitosis on

Epiphysis side of the

plate

• cartilage cells are

destroyed and replaced

by bone on Diaphyseal

side of the plate

o Ages 18 to 25, Epiphyseal

plates close.

• cartilage cells stop

dividing and bone

replaces the cartilage

(Epiphyseal line)


GROWTH IN LENGTH –

e.g. EPIPHYSEAL PLATE

End result: extension of bone length


GROWTH IN THICKNESS –

e.g. PERIOSTEUM OF LONG BONEBone can grow in thickness or diameter only by

appositional growth.


BONE REMODELING

Remodeling is the ongoing replacement of old bone tissue by

new bone tissue. 2 stages:

1. Bone deposition – construction of new bone by

osteoblasts

2. Bone resorption – destruction of old bone by

osteoclasts; osteoclasts form leak-proof seal around cell

edges and secrete enzymes (digest collagen) and acids

(dissolve minerals) beneath themselves and release

calcium and phosphorus into interstitial fluid through

process of endocytosis and exocytosis

Why is bone remodelling important?


FRACTURE AND REPAIR OF BONE

o A fracture is any break in a

bone structure.

o Healing is faster in bone than in

cartilage due to lack of blood

vessels in cartilage.

o Healing of bone is still slow

process due to vessel damage.

o Clinical treatment: closed or

open reduction.


REPAIR OF BONE FRACTURE

Step 1: Formation of fracture

haematoma

• damaged blood vessels

produce clot in 6-8

hours, bone cells die

• inflammation brings in

phagocytic cells for

clean-up duty

• new capillaries grow into

damaged areaAlso see BIOS222


REPAIR OF BONE FRACTURE

Step 2: Formation of

fibrocartilaginous callus

formation

• fibroblasts invade the

procallus & lay down

collagen fibers

• chondroblasts produce

fibrocartilage to span the

broken ends of the bone


REPAIR OF BONE FRACTUREStep 3: Formation of bony callus

• osteoblasts secrete spongy bone that joins 2 broken ends of bone

• lasts 3-4 months

Step 4: Bone remodeling

• compact bone replaces the spongy bone in the bony callus

• surface is remodeled back to normal shape


REGULATION OF BONE

PHYSIOLOGY

o Endocrine regulation – parathyroid hormone levels

regulate release of Ca2+ from stores (skeleton) into the

blood supply to be used by other systems (e.g. Ca2+

regulates nerve and muscle function and blood clothing)

– details of this regulation see BIOH111, session 24

o Exercise (mechanical stress) - within limits bone has the

ability to alter its strength in response to mechanical

stress by increasing deposition of mineral salts and

production of collagen fibers, making the bones stronger


REGULATION OF CALCIUM BLOOD

LEVELS

o Parathyroid hormone (PTH) is secreted if

Ca+2 levels falls

• PTH gene is turned on & more PTH is

secreted from PT gland

• osteoclast activity increased, kidney

retains Ca+2 and produces calcitriol

o Calcitonin hormone is secreted from

parafollicular cells in thyroid if Ca+2 blood

levels get too high

• inhibits osteoclast activity

• increases bone formation by

osteoblasts

Linking point to BIOH111, Session 24


Recap of Session 9

Bones contain several different cell types that are responsible for some

of the overall functions of the skeletal system

Long bone contains parts that ensure some of the functions of the

overall skeletal system

Bones can grow in length and width

Bones are able to heal a fracture through a series of steps

A specific bone cell is important in regulation of calcium levels in the

blood as it is regulated by hormones


PREPARATION FOR NEXT SESSION

o Complete missing concepts and linking words from

Session 9

o Review overall functions of the skeletal system

o Write down any bone names you know (you will learn

latin names for these in the next session)


Revision videos

https://www.youtube.com/watch?v=0dV1Bwe2v6c

Regulation of osteoclast activity-cell signalling via RANK

https://www.youtube.com/watch?v=GpMV197xZXc

https://www.youtube.com/watch?v=0dV1Bwe2v6c

https://www.youtube.com/watch?v=GpMV197xZXc

bioh111 sn09 skeletal system · edition: chapter 6 © endeavour college of natural health...

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