Skeletal System

Front 1

The skeleton is

Back 1

the body’s framework

Front 2

The skeleton also

Back 2

supports & protects our organs & allows us to move

Front 3

Functions of Skeletal System

Back 3

Support
Protection
Movement
Blood cell production
Storage

Front 4

Support

Back 4

Bone provides a framework for the body
Supports soft tissues
Provides points of attachment for many skeletal muscles

Front 5

Protection

Back 5

Encloses organs to protect them
Skull: protects brain
Rib cage: protects lungs, heart

Front 6

Movement

Back 6

Contraction of skeletal muscle causes bones to move
Joints are where 2 or more bones articulate, allowing the bones to move together to produce different types of movements

Front 7

Blood cell production

Back 7

Bone marrow found in the cavities of bones produce blood cells & platelets
This process is called hemopoiesis

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hemopoiesis

Back 8

Bone marrow found in the cavities of bones produce blood cells & platelets

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Storage

Back 9

Fat, Ca++ (Calcium) & PO4ˉ (Potassium) are stored in bone from the blood stream
If needed they are released back into the blood stream to be used elsewhere by the body

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There are #? named bones

Back 10

There are 206 named bones

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Bones Are

Back 11

lightweight & are continually broken down & reformed

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skeleton includes

Back 12

Cartilage, tendons & ligaments also form part of the skeleton

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Muscles

Back 13

act on bone through tendons to produce movement

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Ligaments

Back 14

join bone to bone

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Cartilage

Back 15

provides support within structures

Front 16

Types of Bone

Back 16

1: Compact bone
2: Cancellous (Spongy) bone

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Bone tissue is

Back 17

not completely solid

Front 18

Bone Contains

Back 18

small spaces for blood vessels & bone marrow

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Type of bone is

Back 19

determined by the matrix & how the cells are organised

Front 20

Compact Bone

Back 20

Forms the external layer of all bones.

Provides protection & support .

Helps bones resist weight bearing stress.

Contains more bone matrix than spaces .

Matrix is tightly packed & arranged in circles (osteon) around a central canal which contain blood vessels & nerves.

Osteocytes found in spaces of the matrix.

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Cancellous (Spongy) Bone

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Also called spongy bone as it resembles a sponge .

Contains more spaces than bone matrix .

Bone matrix is made up of interconnecting beams of bone called trabeculae.

Osteocytes exist within the trabeculae .

Osteoblasts & osteoclasts exist on the walls of the trabeculae .

Blood vessels & bone marrow fill the canals between the trabeculae.

Found where strength but lightness is required.

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Bone Classification

Back 22

Bones are organs

Front 23

Bones are Classified according to their shape

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1. Long.
2. Short.
3. Flat .
4. Irregular .
5. Sesamoid .
6. Sutural .

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1. Long bones

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Length is > than width & slightly curved for strength.

A curved bone absorbs the stress of the body weight at several points so the stress is evenly distributed.

Mainly compact bone with large amounts of spongy bone .

Eg. Tibia, fibula, femur, humerus, phalanges, radius, ulna.

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Structure of Long Bone Has 3 major components

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1. Diaphysis: long shaft of the bone.
Composed mainly of compact bone.
Has a hollow centre called the medullary cavity
2. Epiphysis: both the distal & proximal ends of the bone.
Consists mainly of spongy bone with an outer layer of compact bone.
Ends of epiphysis that make up a joint is covered in articular cartilage.
3. Epiphyseal plate: also termed metaphysis .
Between where the diaphysis & epiphysis meet .
Contains a thin layer of hyaline cartilage & is where bone growth occurs.
Becomes ossified when bone growth ceases.

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Medullary Cavities of Bones

Back 26

Provide channels for blood vessels & storage of bone marrow.
Fatty yellow marrow (adipose tissue) exists in cavities of skull & limb bones.
Red bone marrow (site of blood cell production) exists in the cavities of the rest of skeleton.
Nerves accompany some blood vessels & other nerves are contained in the periosteum.

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Blood Cell Production

Back 27

Haemopoiesis is the formation of blood cells.
Occurs in red bone marrow of vertebrae, ribs, sternum, skull & some long bones.
In children blood cells are produced in the marrow of almost all bones.
Prior to birth, blood cells are also produced in the liver, spleen & lymph nodes.

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Haemopoiesis

Back 28

is the formation of blood cells.

Front 29

Short Bones

Back 29

Cube shaped nearly equal in length & width.
Spongy bone except the surface which is a thin layer of compact bone.
Eg, carpals, tarsals in wrists & feet .

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Structure of Short Bones

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have no diaphysis .

structure is similar to epiphysis of long bones .

spongy bone with an outer layer of compact bone .

Front 31

Flat Bones

Back 31

Generally thin & composed of 2 parallel plates of compact bone with spongy bone in between.
Provide protection & extensive areas for muscle Attachment.
Eg, cranium, sternum, scapulae.

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Structure of Flat Bones

Back 32

have no diaphysis or epiphysis.

consist mainly of spongy bone .

Sandwiched between 2 layers of compact bone.

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Irregular Bones

Back 33

Complex shaped & do not fit into any other group.
Eg, vertebrae, some facial bones, pelvic bones.

Front 34

Structure of Irregular Bones

Back 34

same as short bone.

have no diaphysis or epiphysis .

consist mainly of spongy bone.

Sandwiched between 2 layers of compact bone.

Front 35

Sesamoid Bones

Back 35

Small bones embedded in tendons where considerable pressure develops.
Eg, thumb, great toe, patella.

Front 36

Sutural Bones

Back 36

Small bones located within the cranial sutures or joints.

Front 37

Outside Surface of Bones

Back 37

Periosteum

Front 38

Periosteum

Back 38

Covers the outer surface of all bones except where hyaline cartilage exists.
Is a doubled layer of connective tissue membrane .
Continuous with tendons & ligaments where they attach to the surface of bone.
Collagen fibres from ligaments & tendons penetrate through periosteum & into outer portion of bone.
This strengthens their attachment to bone.

Front 39

Inside Surface of Bones

Back 39

Endosteum

Front 40

Endosteum

Back 40

Also a connective tissue that covers all inner surfaces within bone.
A thin single layer of cells lining the medullary cavity & spaces in compact & spongy bone.
Contains blood vessels.

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Ends of Bones

Back 41

Hyaline Cartilage

Front 42

Hyaline Cartilage

Back 42

Covers the ends of bones where a joint is formed.
Growth occurs at the hyaline cartilage.
Increases the size of epiphysis.
Also increases the size of bones that do not have an epiphysis.
Provides shock absorbency.

Front 43

Bone Cells

Back 43

Important in growth, maintenance & repair of bone.

Front 44

Osteoblasts

Back 44

produced from stem cells & are the bone forming cells that create the matrix of bone & mineralises bone.

Front 45

Osteocytes

Back 45

are mature osteoblasts & they maintain the matrix.

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Osteoclasts

Back 46

made in the red bone marrow & are responsible for the breakdown of bone (resorption).
They have a ruffled border which has an acid environment causing decalcification of bone .

Front 47

Bone Formation

Back 47

Remember bone is connective tissue.
Consists of bone cells widely separated by an abundant extracellular bone matrix.
Matrix is produced by osteoblasts .
Matrix is made up of collagen (35%) & calcium phosphate crystals (65%).
Endoplasmic reticulum & ribosomes in osteoblasts produce collagen .
The collagen is then packaged by the golgi apparatus (post office) & released by exocytosis from the cell.
The osteoblasts also form vesicles filled with Ca2+, PO42- ions & enzymes .
When these are released from the cell they form a mineralised bone matrix .

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Collagen

Back 48

provides the reinforcing supports which are flexible.
Without the collagen, bone would be very brittle.
When a bone bends slightly toward one side the tensile strength of collagen fibres prevents it from snapping.

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Mineral salts

Back 49

are deposited into the framework made by the collagen fibres .
As the salts crystallise the bone hardens or calcifies the mineral component allows bones to support the weight of the body.

Front 50

Bone growth occurs in 3 ways

Back 50

1. Longitudinally.
2. On hyaline cartilage .
3. Width.

Front 51

Bone Growth

Back 51

The embryo’s skeleton is made up of hyaline cartilage which is converted to bone by birth .
Bones grow by forming new bone on the surface of old bone.

Front 52

Bone Growth -Longitudinal

Back 52

Occurs at the epiphysial plate in long bones.
Cartilage cells are produced they multiply & then enlarge at the top of the plate which then goes through a process of calcification .
Osteoblasts then deposit onto the bottom (on the diaphysis side) of the calcified cartilage.
This forms a new bone matrix & adds bone to the diaphysis, increasing its length .
Between the ages of 12-25 the epiphyseal plate ossifies & growth ceases.

Front 53

Bone Growth -On Hyaline Cartilage

Back 53

Increases the size of epiphyses.
Also on bones that do not have epiphyses.
Hyaline cartilage that is nearest to bone calcifies, dies & is ossified to produce new bone.
The growth of the cartilage ceases when the epiphyses reaches its full size .
Production of new bone also ceases.

Front 54

Bone Growth -Width

Back 54

Growth in width (thickness).
Osteoblasts add bone underneath the periosteum .
This surrounds a blood vessel on the periosteum & continues until bone forms a circle & the ends meet.
A central canal is formed in the middle & the periosteum becomes the endosteum within the canal .
This produces an osteon.

Front 55

Factors Affecting Bone Growth

Back 55

Growth is controlled by the human growth hormone (HGH) produced by the anterior pituitary gland .
Over secretion of HGH causes gigantism.
Dwarfism is caused by under secretion of HGH.
At puberty oestrogens & testosterone are responsible for the growth spurt in teenagers.
Oestrogen is also responsible for skeletal changes e.g. wider pelvis in females.

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Normal bone growth depends on:

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Minerals - Calcium, phosphorous, magnesium, boron, manganese.
Vitamins: - A, B12, C & D.
Hormones: -HGH, sex hormones, insulin, thyroid hormone, calcitonin & parathyroid hormone.
Exercise .
Bone is able to alter its strength in response to mechanical stressors.
Mineral salts are deposited & more collagen fibres are produced.
Stress also increases the production of the hormone calcitonin which inhibits bone resorption (back into the blood stream).
If bedridden, the loss of bone can be as much as 1% a week.

Front 57

Bone Remodelling

Back 57

Osteoclasts are responsible for the resorption of matrix (destruction of matrix).
A balance exists between osteoclast removing material & the osteoblast making new bone.
New cells are produced & the matrix hardens when calcium (Ca2+) & other mineral salts are deposited.
If too much mineral is deposited thick bumps can form which interferes with movement.
If too little Ca2+ is deposited, bones will weaken & break easily (osteoporosis) or become too flexible (ricketts).
Bone is remodelled in response to Ca2+ levels in the blood & the pull of gravity (muscles of the skeleton) .

Front 58

Calcium Homeostasis

Back 58

Bone stores 99% of the body’s calcium.
The blood levels of Ca2+ are closely regulated by the body.
When the blood level of calcium decreases, parathyroid hormone is released.
Osteoclasts are activated & the bone matrix is broken down.
Ca2+ is then released into circulation .
This is called resorption.
When blood levels of Ca2+ ↑, calcitonin is released
Calcitonin influences Ca2+ from the blood & is deposited in bone.
Maintenance of blood levels of Ca2+ is important for nerve cell function, muscle contraction, heart function & breathing.
This is a negative feedback system.

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Calcium Homeostasis & Ageing

Back 59

Loss of calcium & bone matrix.
Loss of Ca2+ occurs after the age of 30 in females, & accelerates between the age of 40- 45.
As levels of oestrogen decrease, loss of Ca2+ & bone matrix occurs.
As much as 30% of Ca2+ is lost from the bones by the age of 70 years.
The process commences at 60 for men.
Protein synthesis decreases.
Less collagen is produced which makes the bones more brittle (decreases tensile strength).

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The Axial Skeleton Consists of

Back 60

Skull.
Vertebrae .
Thorax (ribs & sternum).

Front 61

Axial Skeleton: Skull

Back 61

8 cranial .
1. Frontal bone .
2 & 3. 2 parietals.
4 & 5. 2 temporals.
6. Occipital.
7. Ethmoid.
8. Sphenoid .

14 facial bones.
2 nasal.
2 maxilla.
2 zygomatic arch.
2 lacrimal.
2 palatine .
2 inferior nasal concha.
Mandible .
Vomer.

Front 62

Cranial Bones

Back 62

Immoveable joints called sutures exist between the cranial bones .
Coronal: suture unites the frontal & 2 parietal bones.
Sagittal: suture unites the 2 parietal bones.
Lambdoid: suture unites the parietal & occipital bones.
Squamous: suture unites the parietal & temporal bones.

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Fontanels

Back 63

The fontanels are membrane filled sacs between some bones which are gradually replaced by bone following birth.
There is an anterior & posterior fontanel.

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Axial Skeleton: Vertebral Column

Back 64

Makes up two fifths of the total height of the body.
Is approx 71cm in men and 61cm in women.
Is a strong, flexible rod that bends anteriorly, posteriorly, laterally & also rotates.
Protects the spinal cord.
Supports the head & trunk.
Ribs & muscles of the back attach to the vertebral column.
Pelvic girdle attached to sacrum.

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Vertebrae Regions

Back 65

There are 34 vertebrae.
Vertebrae vary in size & shape.

Divided into regions according to shape & size.

7, C = Cervical.
12, T = Thoracic.
5, L = Lumbar.
5 fused into 1, S = Sacrum.
4 fused into 1, C = Coccyx.

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Vertebrae

Back 66

The body is the thick weight bearing part.
The arch contains a vertebral foramen (opening for the spinal cord).
The vertebral foramina is found in all vertebrae & this forms a ring called the spinal canal .
The spinal canal contains the spinal cord.

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Intervertebral Foramina

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Between the vertebrae are openings called the intervertebral foramina .
Nerves from the spinal cord that supply other parts of the body pass through these openings.

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Vertebrae

Back 68

Each vertebrae has seven processes. (spikes)
Transverse process & spinous process serve as points of attachment for the muscles.
The other four processes form joints with other vertebrae.

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Intervertebral Discs

Back 69

The outer part of the disc is the fibrocartilage.
The centre is soft & pulpy & highly elastic.
The discs form strong joints which absorb vertical shock.
Under compression they flatten, broaden & bulge from their intervertebral spaces.

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Vertebral Columns

Back 70

The vertebral column has four curves.
Cervical & lumbar are convex.
Thoracic & sacral are concave.

Top to bottom:
Cervical ,
Thoracic ,
lumbar &
sacral .

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Cervical Region

Back 71

Cervical vertebra are smaller than thoracic.
C1 (atlas) supports the head {think atlas supporting the world on his shoulders}.
It allows nodding of the head (nodding for yes).
C2 (axis) acts as a pivot on which the atlas and head rotate.
It allow side to side rotation (turning head from side to side for no).

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Thoracic Region

Back 72

Thoracic vertebrae are considerably larger & stronger than cervical.
Facets on the vertebrae articulate with the ribs.
Movement of the thoracic region is limited by the thin intervertebral discs & attachment of the ribs to the sternum.

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Lumbar Region

Back 73

Body of these vertebrae are the thickest.
Arrangement of vertebrae is to add strength but this limits its ability to rotate.
Large muscles of the back attach to them.

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Sacrum

Back 74

Triangular bone formed by the union of five sacral vertebrae.
Female sacrum is shorter, wider & more curved between S2 & S3 than the male.
Coccyx: Triangular shaped & formed by the fusion and four coccygeal vertebrae.

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Axial Skeleton: Thorax

Back 75

The thorax is the entire chest.
Consists of the
sternum,
costal cartilage,
ribs ,
bodies of the thoracic vertebrae.
Encloses & protects the organs in the thoracic cavity & upper abdominal cavity.

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Sternum

Back 76

Sternum is 15cm long.
Consists of manubrium, body & xiphoid process.
Sternal angle is the junction of the manubrium & body.
Suprasternal notch is the depression in the anterior surface of the manubrium.

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Ribs

Back 77

12 pairs.
True ribs: 7 pairs attached to the sternum by costal cartilage (hyaline).
False ribs: 3 pairs 8,9, and 10 attach to each other and then to the cartilage of the 7th rib.
Floating ribs: 2 pairs (also false) the anterior ends do not attach to the sternum.

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Intercostal Spaces

Back 78

Spaces between the ribs.

Occupied by the intercostal muscles, blood vessels & nerves .

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The Appendicular Consists of

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Upper and lower limbs.
Pelvic girdle.
Pectoral girdles.

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Appendicular Skeleton

Back 80

Consist of the bones of the upper & lower limbs & the girdle that attaches the bones of the limb to the body.

Upper limbs:
Humerus,
Ulna ,
Radius ,
Carpals,
Metacarpals &
Phalanges .

Pectoral Girdle: (shoulder):
Clavicle &
Scapula.

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Lower limbs:

Back 81

Femur,
Tibia,
Fibula,
Malleolus,
Talus,
Calcaneus,
Tarsals,
Metatarsals &
Phalanges .

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Pelvic Girdle:

Back 82

Ilium,
Ischium &
Pubis .

Pelvis - formed by the sacrum, coccyx & hip bones.

Front 83

Joints / Articulations

Back 83

A joint or articulation is a point of contact between bones, cartilage & bones or between teeth & bones.
All bones form a joint with at least one other bone.
An exception is the hyoid bone: a horse shaped bone which provides a moveable base for the tongue).
Joints hold bones together securely & give the skeleton mobility.

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Classification of Joints

Back 84

All joints consist of bony regions separated by cartilage of fibrous connective tissue.
Classified by joint structure & function.

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Structure:

Back 85

Fibrous ,
Cartilaginous &
Synovial .

Front 86

Function: Degree of movement:

Back 86

Synarthrotic,
Amphiarthrotic &
Diarthrotic .

Front 87

Joint Structure - Fibrous joints.

Back 87

Two bones that are bound by a fibrous connective tissue.
Don’t have a joint of cavity.

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Joint Structure - Synarthrotic joint:

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Little or no movement.
Sutures: bones are aligned e.g. seams of the skull.
Syndesmoses: bones are apart & ligaments form the join e.g joint of tibia & fibular.
Gomphoses: pegs that fit into a socket e.g teeth & their sockets.

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Joint Structure - Cartilaginous Joints

Back 89

Bones are held together by hyaline or fibro cartilage.
Hyaline cartilage: little or no movement, most are temporary e.g. epiphyseal plates of growing bones.
Joints between ribs & sternum. these joints usually become synovial joints except for the first costal cartilage.
Fibrocartilage: Amphiarthrotic: Joints are slightly moveable e.g. Pubic symphysis, intervertebral discs.

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Joint Structure - Synovial Joint

Back 90

All synovial joints have 4 distinguishing features:
A capsule encloses the bones & holds them together within the joint.
A synovial space separates the bones.
Hyaline cartilage covers bones on the opposing surfaces within the joint.
A synovial membrane .

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Synovial Joint- Diarthrotic

Back 91

Freely moveable joints allowing several different types of movement.
Gliding joints – carpals and tarsals.
Hinge joint – humerus and ulna.
Pivot joint – radius and ulna.
Condyloid joint – radius and carpals.
Saddle joint –carpal and metacarpal of thumb.
Ball and socket joint – femur and hip.

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Synovial Capsule, Consists of 2 layers

Back 92

1. A fibrous layer joins the bones.
2. A synovial membrane lines the capsule.
The fibrous layer permits flexibility & provides tensile strength which prevents dislocation.
Dense irreg connective tissue.
Continuous with periosteum of the bone.
Parts of the capsule form ligaments.
Tendons & ligaments also outside the capsule contributing to stability & allowing certain types of movement.

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Synovial Membrane

Back 93

Lines the entire joint cavity except over the ends of the bones covered in hyaline cartilage.
The synovial membrane consists of areolar connective tissue with elastic fibres & adipose tissue.
It secretes synovial fluid, contains serum & secretions from synovial cells.
The fluid helps reduce friction, provides nutrients, & contains phagocytic cells.

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Synovial Space

Back 94

The articulating bone ends are separated by a joint space.
Contains synovial fluid.
Synovial joints contain bursae (sacs that are also filled with synovial fluid) .
They cushion tendons where they cross bone.

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bursa
Type: Term Pronunciation: ber′să, ber′sē Definitions:

Back 95

1. A closed sac or envelope lined with synovial membrane and containing synovial fluid, usually found or formed in areas subject to friction (over an exposed or prominent body part or where a tendon passes over a bone).