Chapter 6: skeletal system - PowerPoint Presentation

Slide1

Chapter 6: skeletal systemChapter 4: skeletal system tissue Slide2

Lesson ObjectivesSkeletal

Discuss the functions of the skeletal system.

Classify bone in the basis of their shape and location.

Describe parts of long bone.

Describe the histological features of bone tissue.

Explain the steps involved in bone formation.

Describe the factors involved in bone growth and maintenance.

Compare the principal structural and functional differences between male and female skeletons.

Tissues

Explain how connective tissue is classified.Slide3

FUNCTIONS OF BONE AND THE SKELETAL SYSTEM

Support

Framework of body; supports soft tissue; provides points of attachment for skeletal muscles (most)

Protection

Of internal organs

Assisting in movement

How? Muscle to bone attachment; muscles contracts pulls on bone

 muscle + bone = movement

Mineral homeostasis

Minerals stored in bone tissue (

Ca

and P); released on demand when needed to other body parts via blood stream

Production of blood cells

 Red Bone Marrow; connective tissueSlide4

Red Bone Marrow

Within connective tissue

Red bone marrow through

hemopoiesis

makes:

Red blood cellsWhite blood cells Platelets Fragment of cytoplasm enclosed in a cell membrane; lacks a nucleusFound in circulating bloodPlays role in hemostasis (stoppage of bleeding)Red bone marrow consists of: Developing red blood cellsAdipocytes (fat cells composed mainly of fat tissue adipose)Fibroblasts (large, flat cells that secrete matrix of extracellular material of aerolar (collagen and elastic tissue) and dense connective tissueMacrophages (white blood cells of immune system)Slide5

Location of Red Bone Marrow

Developing bones of fetus and some adult bones

Pelvis

Ribs

Sternum

Vertebrae

Skull

Ends of arm and thigh bonesSlide6

FUNCTIONS OF BONE AND THE SKELETAL SYSTEMSupport

Protection

Assisting in movement

Mineral homeostasis

Production of blood cells

Triglyceride storage

In adipose tissue or yellow bone marrowSlide7

Yellow Bone Marrow

Yellow bone marrow consists of adipose tissue and some blood cells

Stores triglycerides in its adipose

tissue

Potential energy

reserve

Adults

 most red bone marrow has changed to yellow bone marrowNot found in newbornsSlide8

TYPES OF BONESFour main types of bones of the body:

Long bones

: have greater length and width, consists of a shaft and a variable number of ends, usually somewhat curved for strength.

Examples

:

thigh (femur), leg (tibia and fibula), arm (

humerus

), forearm (ulna and radius), and fingers and toes (phalanges)Slide9

TYPES OF BONESFour main types of bones of the body:

Short

bones

: somewhat cube-shaped and nearly equal in length and width.

Examples

:

most wrist and ankle bonesSlide10

TYPES OF BONES

Four main types of bones of the body:

Flat

bones

: generally thin,

offer

considerable protection, have extensive surface areas for muscle attachment.

Examples: cranial bones (protect the brain), sternum/breastbone and ribs (protect organs in thorax), pelvis (protects digestive and reproductive organs),and scapulae (shoulder blades)Slide11

TYPES OF BONES

Four main types of bones of the body:

Irregular

bones

: complex shapes

Examples

:

vertebrae of the backbone and some facial bonesSlide12

STRUCTURE OF BONEMacroscopic Structure of Bone

Microscopic Structure of BoneSlide13

Macroscopic Structure of Bone

Parts as they relate to a long bone with greater length than width

Diaphysis:

bone’s

shaft or

body; long

, cylindrical, main portion of

boneEpiphyses: distal and proximal ends of bonesMetaphyses: regions in a mature bone where diaphysis joins epiphyses; in growing bone each metaphyses includes an epiphyseal plate, layer of hyaline cartilage that allows the diaphysis of bone to grow in length; when bone growth in length stops, cartilage in epiphyseal plate replaced by bone and this bony structure is now known as the epiphyseal lineSlide14

Macroscopic Structure of Bone

Articular cartilage: thin layer of hyaline cartilage covering part of the epiphysis where bone forms a joint (articulation) with another bone; it reduces friction and absorbs shock; lacks a perichondrium so repair of damage is limitedSlide15

Macroscopic Structure of Bone

Periosteum

: tough sheath of dense irregular connective tissue surrounding a bone’s surface wherever it lacks articular cartilage; consists of bone-forming cells enabling bone to grow in diameter or thickness; protects the bone, assists in fracture repair, helps nourish bone tissue, serves as attachment point for ligaments and tendonsSlide16

Macroscopic Structure of Bone

Medullary

cavity: marrow cavity; space within diaphysis containing yellow bone marrow in adults

Endosteum

: thin membrane lining medullary cavity; contains single layer of bone-forming cellsSlide17

Microscopic Structure of Bone

Composition of intracellular materials of the bone, or osseous tissue

matrix:

25%

water

25%

collagen fibers (protein)

50% crystallized mineral saltsCalcification: mineral salts are deposited into a framework formed by collagen fibers they crystallize and tissue hardensCalcification is initiated by: osteoblasts; bone-building cells_Hardness of bone depends on crystallized inorganic mineral saltsFlexibility depends on collagen fibersTensile strength is provided by

collagen

fibers and other

organic

molecules that offer resistance to

being

stretched or torn

apartSlide18

Four Major Types of Bone Tissue

Osteogenic cells=> producing = unspecialized stem cells

Osteoblasts=> blasts = buds or sprouts

Osteocytes =>

cytes

= cells

Osteoclasts =>

clasts = breakSlide19

Spaces between cells and matrix are for:channels for blood vessels (supply bone with nutrients)storage

for red blood

marrow

Composition of skeleton: BASED ON SIZE AND DISTRIBUTION OF

SPACES

80%

compact bone

20% spongy boneSlide20

Compact Bone TissueContains few spaces; forms external layer of all bones; makes up bulk of diaphysis of long

bone

; provides protection and support; resists stress produced by weight and movement

Spongy Bone Tissue

Makes

up most of the bone tissue of short, flat, and irregularly shaped bones; forms most of

epiphyses

of long bone and a narrow rim around the medullary cavity of the diaphysis of long bones.Slide21

Compact Bone Tissue

Pages 127-129 explain how these structures provide routes for nutrients and oxygen to reach osteocytes and for waste to diffuse awaySlide22
Slide23

Spongy Bone Tissue

Trabeculae

: little

beams; irregular latticework of thin columns of bone; spaces between filled with red bone marrowSlide24

Dense or Compact Bone

Spongy or Cancellous Bone

Hardness

Mostly solid

Bony structures with spaces filled with bone marrow

Consists of

Osteocytes in lacunae

Osteocytes in lacunae

Location

Covers all bone surfaces; except where they could rub

Short, flat bones, inside ends of long bones

Functional units

Osteons or haversian systems

Trabeculae

filled with red bone marrow

Stress tolerance

High end to end; low from side

Not on heavy stress areas, can take stress from any direction- disperses itSlide25

Bone ScansDarker spots = ‘hotspots’

lighter spots = ‘

coldspots

’Slide26

OSSIFICATION: BONE FORMATION

Ossification: process by which bone forms

Site

of

ossification: loose

fibrous connective tissue membranes and pieces of hyaline cartilage, shaped like little bones in embryonic

skeletonSlide27

Four Principle Situations

Initial formation of bones in embryo and fetus

Growth of bones during infancy, childhood, and adolescence until adult sizes are reached

Remodeling of bone (replacement of old bone tissue by new bone tissue throughout life)

Repair of fractures (breaks in bones) throughout lifeSlide28

Initial Bone Formation in an Embryo and FetusFirst composed of mesenchyme shaped liked bones, sites/templates where ossification will occur

Ossification begins during the sixth week of embryonic development and follows one of two patterns

Intramembranous ossification

Endochondral ossificationSlide29

Two methods of bone formation

Intramembranous Ossification

Bone forms directly in mesenchyme arranged in

sheetlike

layers resembling

membranes; directly

on or within loose fibrous connective tissue

membranesEndochondral OssificationBone forms within hyaline cartilage that develop from mesenchymeSlide30

Intramembranous Ossification

Simplest of two

methods

-Forms flat

bones of skull and mandible (

lower

jawbone

) -Replaces ‘soft spot’ on fetal skull ______________Slide31
Slide32

Endochondral OssificationReplacement of

hyaline cartilage

by bone.

Most bone in the body below the skull except the clavicles are formed this waySlide33
Slide34

Bone Growth in Length and ThicknessLong bones grow during infancy, childhood, and

adolescenseSlide35

Growth in Length

Through the activity of the epiphyseal plate

Young chondrocytes divide in the epiphyseal plateSlide36

Growth In Thickness

As bones lengthen, they thicken

Cells in perichondrium differentiate into osteoblasts that secrete bone extracellular matrix

Osteoblasts develop into osteocytes, lamellae added to bone surface and new osteons of compact bone tissueSlide37

Bone Remodeling

Remodeling: ongoing replacement of old bone tissue by new bone

tissueSlide38

COMMON DISORDERS---PAGE 133FRACTURES

fracture

:

any

break in a

bone

Four

different types of fractures (1) partial: incomplete break across the bone; i.e. a crack(2) complete: complete break across the bone; bone broken in two or more pieces(3) closed (simple): fractured bone does not break through skin(4) open (compound): broken ends of bone protrude through skinSlide39

Fracture Repair

What happens when a bone breaks?

OUCH!!!Slide40

First step: phagocytes begin to remove dead bone tissueSecond step: chondrocytes form fibrocartilage at fracture site that bridges the broken ends of

bones

Third step: fibrocartilage converted to spongy bone tissue by osteoblasts

Fourth step: bone remodeling occurs, dead portions are absorbed by osteoclasts and spongy bone converted to compact boneSlide41

Factors Affecting Bone Growth and RemodelingFactors that control bone metabolism:

Minerals: Ca, P, Mg need adequate amounts of each

Vitamins: A, C, D

Hormones: hGH, IGFs (insulin-like growth factors; produced locally by bone and by the liver when stimulated by hGH ), insulin, thyroid hormones, parathyroid hormones, calcitonin

hGH: _main hormone before puberty that stimulates bone growth; produced by anterior lobe of pituitary gland

over secretion of hGH: produces

giantism

, person becomes taller and heavier than normalunder secretion of hGH: _produces dwarfism, short statureSlide42

Stress (weight bearing exercise)

Mineral

crystals generate

: production

of collagen fibers, bone

mass

Osteoblasts

are: bone-forming cellsHeavily stressed bones are: notably thicker; builds & retains bone massUnstressed bones become: lose strength; loss of bone mass Example: leg in cast up to ~30% of bone massExamples of serious bone health risks: bedridden or paralyzed patientspeople in weightless environments Slide43

Bone’s Role in Calcium Homeostasis

Bone

stores

99%

of the total amount of calcium in the body.

Calcium

become available to other

tissues when broken down during remodeling (replacement of old bone with new bone)Effects of small changes in blood calcium levels:Too high: heart may stop Too low: breathing may ceaseSlide44

Bone’s Role in Calcium Homeostasis

Nerve cell functions depend on the right levels of

Ca

2+

Enzymes require

Ca

2+

, as a cofactor (non-protein component of enzymes bound to proteins and required for biological functions).Blood clotting requires Ca2+.Function of bone in calcium homeostasis in blood calcium levelsto “buffer” the blood calcium level, releasing Ca2+ to the blood when blood calcium levels falls and depositing Ca2+ back in bone when blood level rises

When levels falls in blood

parathyroid hormone (

PTH) regulates

Ca

2

+

and is produced by parathyroid glands

When levels rise in blood

calcitonin

(CT

) produced by thyroid glandSlide45

Negative Feedback System

Regulation of blood calcium (Ca

2+

) levelsSlide46

Exercise and Bone Tissue

Bone alters its strength in response

to mechanical stress

HOW????

Increased deposition of mineral salts and production of collagen fibers

Without mechanical stress bone does not remodel normally because

resorption outpaces bone formation.Slide47

Comparison of Female and Male SkeletonsSlide48

Aging and the Skeletal System

Birth to adolescence=> more bone produced than lost

Young adults=> rate of production to loss about equal

Middle age=> decrease in bone mass

WHY???

Levels of sex steroids lowered

Greater problem for female; less bone mass to begin with = more osteoporosis in females

Females age 30 bone loss starts; about age 45 estrogen levels decrease; by age 70 -30% of bone calcium lostMales begins around age 60, then loss of about 3% of bone mass every 10 yearsSlide49

CHAPTER 4 TISSUESSlide50

Types of Tissues

(1) Epithelial

-covers body surfaces; body cavities, hollow

organs, and ducts; forms glands

(2) Connective

-protects and supports the body and its organs, binds organs together, stores energy reserves as fat, provides immunity(3) Muscular -generates physical force to move body structures (4) Nervous -detects changes inside and outside the body, initiates and transmits nerve impulses that aid in homeostatic maintenanceSlide51

Cell Junctions

Point of contract between plasma membranes of tissue cells

As each osteocyte lays matrix, it gets sealed into its own room and they reach out to the next osteocyte and  communicate by 

gap junctions

(type of cell junctions) called

lacunae even though they are very isolatedSlide52

Connective Tissue:General Features of Connective Tissue

Consists of two basic elements: cells and extracellular matrix

Highly vascular (have a rich blood supply)

Has nerve cells; cartilage does not

Extracellular matrix

 materials between widely spaced cells composed of protein fibers and ground substance (materials between cell ands and fibers)

Cartilage and tendons are avascular…Slide53

Connective Tissue Cells

Read through the types on pages 88-89; which one(s) are found in bone connective tissue?Slide54

Connective Tissue Extracellular MatrixGround substance

Between the cells and fibers

Supports cells, binds them together, provides medium through which substances are exchanged between the blood and cells

Chondroitin sulfate ground substance is found in bone

and cartilage

Provides support and adhesiveness in bone connective tissues

Fibers Strengthen and support connective tissuesRead page 90 for rest of information…Slide55

Classification of Connective Tissues

1. Loose Connective Tissue

a.

areolar connective tissue---not applicable to

bones

note: only truly found in joint areas  b. adipose tissue---yellow bone marrow, padding around joints function: serves as energy reserve; support c. reticular connective tissue---red bone marrow (gives rise to RBCs); cells that make the reticular

fibers are

fibroblasts

function:

filters and removes worn-out blood

cells; forms

a scaffolding for

bone marrow

 Slide56

Three Types of Fibers

Loose connective tissue is composed of loosely woven collagen and elastic fibers. The fibers and other components of the connective tissue matrix are secreted by

fibroblasts (i.e.: reticular fiber).Slide57

Continued…

2

. Dense Connective Tissue

a.

dense regular connective tissue---forms tendons (attach

muscle to bone

), most ligaments (attach bone to bone), and aponeuroses (sheet-like tendons attach muscle to muscle or muscle to bone) function: provides strong attachment between structures, allows them to resist pulling (tension) b. dense irregular connective tissue---periosteum of bone,

periosteum

of cartilage, joint capsules

function: provides tensile (pulling) strength

c.

elastic connective tissue---not applicable to

bones

*****

NOTE: FOUND IN SOME LIGAMENTS

BETWEEN VERTEBRAE

 Slide58

Continued…

3. Cartilage

Consists

of:

dense network of collagen fibers embedded in

chondroitin sulfate

Strength

is due to: collagen fibers Resilience due to: chondroitin sulfate (rubbery component of ground substance) Cells called chondrocytes (mature cartilage) are found in lacunae lacunae  like little lakes within extracellular matrix Perichondrium (dense irregular connective tissue) surrounds the

surface

of

cartilage

Cartilage is different

from other types of connective

tissue because

it does not have a blood supply or nerves and it secretes

antiangiogenesis

factor (substance that prevents blood vessel

growthSlide59

Three Types of Cartilage

(1) hyaline cartilage

(most common; weakest)

Consists

of:

resilient

gel as its ground substance; appears in body as bluish-white shiny

substanceProperties: compressible, flexible, insensitiveLocations: ribs to sternum; supporting larynx, trachea, and bronchia; bone ends at synovial joints; part of large septumSlide60

Three Types of Cartilage

(2)

fibrocartilage

(strongest)

Consists

of:

chondrocytes

scattered among bundles of collagen fibersLacks: perichondriumProperties: strength and rigidityLocation: discs between vertebrae, pads of knee jointsSlide61

Three Types of Cartilage

(3)

elastic cartilage

Consists

of:

chondrocytes

within threadlike network of elastic

fibersProperties: strength and elasticity; maintains shape of certain structures; i.e. external earLocations: auricle of external ear; epiglottis and part of larynx; auditory canalSlide62

Bone Tissue

SHOULD

READ COMPOSED OF…

bone

or osseous

tissue

periosteum

red and yellow bone marrowendosteumMain component of compact bone: Osteon of Haversian systemMain component of spongy bone: TrabeculaeSlide63

Bone Tissue FunctionsSupports soft tissue

Protects delicate structures

Works with skeletal muscles to generate movement

Stores calcium and phosphorus

Stores red bone marrow

Storage site for triglyceridesSlide64

Membranes

Synovial membranes (flat sheets of pliable tissue) line the cavities of some joints

Location

:

joints areas of bone

Types

of tissue:

composed of areolar connective tissue and adipose tissue with collagen fibersFunction: secretes synovial fluid from its synoviocytes that lubricates ends of bones as they move at the joints, nourishes cartilage, removes microbes and debris from joint cavitySlide65

Muscular Tissue- page 98Tissue Repairing: Restoring Homeostasis- pages 98-99Aging and Tissues- page 100

You are responsible for this material on your ownSlide66