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The Skeletal System. Dr. S. Nishan Silva (MBBS). Under the Skeletal System. Function Classification Histology Formation Gross Anatomy. Function of the Skeletal System. Support- framework that supports body and cradles its soft organs Protection- for delicate organs, heart, lungs, brain

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dr s nishan silva mbbs

The Skeletal System

Dr. S. Nishan Silva

(MBBS)

under the skeletal system
Under the Skeletal System
  • Function
  • Classification
  • Histology
  • Formation
  • Gross Anatomy
slide3

Function of the Skeletal System

  • Support- framework that supports body and cradles its soft organs
  • Protection- for delicate organs, heart, lungs, brain
  • Movement- bones act as levers for muscles
  • Mineral storage- calcium & phosphate
  • Blood cell formation- hematopoiesis
functions
Functions:

Support

The bones of the legs, pelvic girdle, and vertebral column support the weight of the erect body.

The mandible (jawbone) supports the teeth.

Other bones support various organs and tissues.

slide5
2.Protection

The bones of the skull protect the brain.

Ribs and sternum (breastbone) protect the lungs and heart.

Vertebrae protect the spinal cord

Movement

Skeletal muscles use the bones as levers to move the body.

slide6
Reservoir for minerals and adipose tissue

99% of the body’s calcium is stored in bone.

85% of the body’s phosphorous is stored in bone.

Adipose tissue is found in the marrow of certain bones

Hematopoiesis

Blood cell formation.

All blood cells are made in the marrow of certain bones

slide7

Types of Bones

  • Long Bones- metacarples, metatarsals, phelangies, humerus, ulna, radius, tibia, fibula
  • Short Bones- carpals, tarsals
  • Flat Bones- rib, scapula, skull, sternum
  • Irregular Bones- vertebrae, some facial bones
  • Sesamoid- patella
classification of bones
CLASSIFICATION of BONES

1.long bones = length is greater than breadth

= consists of shaft (diaphysis) &

two extremities (epiphysis)

diaphysis = filled with yellow marrow

= cylindrical, large space or canal at the center

= periosteum

epiphysis = made up of cancellous tissue

e.g.: femur, humerus, tibia, fibula, radius, ulna, phalanges

Membranes: 1. periosteum

2. endosteum

bone classification
Bone Classification

Long Bones

Much longer than they are wide.

All bones of the limbs except for the patella (kneecap),

and the bones of the wrist and ankle.

Consists of a shaft plus 2 expanded ends.

Your finger bones are long bones even though they’re very short

classification of bones cont n
CLASSIFICATION of BONES cont’n.

2. short bones = cuboidal in shape

= spongy bone with thin coat of compact bone

= sesamoid bone -- short bone embedded in a

tendon e.g.: patella

e.g.: carpals (wrist), tarsal (ankle) bones

3. flat bones = broad or elongated flat plates

= for protection & muscle attachments

composition: 2 thin layers of compact tse. enclosing

a thin layer of spongy bone

e.g.: bones of the skull, sternum, ribs, scapula

slide11
2. Short Bones

Roughly cube shaped.

Bones of the wrist and the ankle.

slide12
Flat Bones

Thin, flattened, and usually a bit curved.

Scapulae, sternum, (shoulder blades), ribs and most bones of the skull.

Sternum

classification of bones cont n1
CLASSIFICATION of BONES cont’n.

4. Irregular bones = all other bones not assigned to the previous groups

e.g.: vertebrae

pelvic bones

bones of the base of the skull

slide14
4. Irregular Bones

Have weird shapes that fit none of the 3 previous classes.

Vertebrae, hip bones, 2 skull bones ( sphenoid and the ethmoid bones).

Sphenoid Bone

slide16

Bone

65% mineral

35% organic

Calcium Phosphste

Hydroxy-apatite

90%

Type 1

Collagen

10%

Other matrix proteins

Lipids

Phospholipids

Proteoglycants

etc

bone cells
Bone Cells
  • Osteoblasts
      • Synthesize matrix; type 1 collagen
  • Osteocytes
      • Control extra-cellular calcium and phosphorus
  • Osteoclasts
      • Synthesize acid phosphatase and hydrogen ions
      • Remove bone minerals and matrix
bone cells1
Bone Cells

Bone tissue is a type of connective tissue, so it must consist of cells plus a significant amount of extracellular matrix.

Bone cells:

Osteoblasts

Bone-building cells.

Synthesize and secrete collagen fibers and other organic components of bone matrix.

Initiate the process of calcification.

Found in both the periosteum and the endosteum

slide19

The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

slide20
2. Osteocytes

Mature bone cells.

Osteoblasts that have become trapped by the secretion of matrix.

No longer secrete matrix.

Responsible for maintaining the bone tissue.

The osteocyte is “trapped” within the pink matrix

slide21
3.Osteoclasts

Huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell).

Cells that digest bone matrix – this process is called bone resorption and is part of normal bone growth, development, maintenance, and repair.

Concentrated in the endosteum.

slide23
Bone Matrix:

Consists of organic and inorganic components.

Organic component consists of several materials that are secreted by the osteoblasts:

Collagen fibers and other organic materials

These (particularly the collagen) provide the bone with resilience and the ability to resist stretching and twisting

slide24
Inorganic component of bone matrix

Consists mainly of 2 salts: calcium phosphate and calcium hydroxide.

Bone also contains smaller amounts of magnesium, fluoride, and sodium.

These minerals give bone its characteristic hardness and the ability to resist compression.

slide25

Anatomy of a Long Bone

spongy bone

Proximal

epiphysis

compact bone

Endosteum

diaphysis

epiphyseal line

yellow marrow

Sharpey’s fibers

Distal

epiphysis

periosteum

hyaline cartilage

2 types of bone
2 Types of Bone

Compact bone

Spongy bone

classification of bones1
CLASSIFICATION of BONES
  • According to structure

1. compact = solid mass; dense & hard

= forms the outer layer of bone structure

= functional unit --- Haversian system

2. cancellous or spongy = contain spaces filled with bone marrow

= incomplete Haversian system

long bone structure
Long Bone Structure

Shaft plus 2 expanded ends.

Shaft is known as the diaphysis.

Consists of a thick collar of compact bone surrounding a central marrow cavity

In adults, the marrow cavity contains fat - yellow bone marrow

slide31
Expanded ends are epiphyses

Thin layer of compact bone covering an interior of spongy bone.

Joint surface of each epiphysis is covered with a type of hyaline cartilage known as articular cartilage. It cushions the bone ends and reduces friction during movement.

slide32
The external surface of the entire bone except for the joint surfaces of the epiphyses is covered by a double-layered membrane known as the periosteum

Periosteum is richly supplied with nerve fibers, lymphatic vessels and blood vessels.

These enter the bone of the shaft via a nutrient foramen.

slide33
Periosteum is connected to the bone matrix via strong strands of collagen

Internal bone surfaces are covered with a delicate connective tissue membrane known as the endosteum.

Covers the trabeculae of spongy bone in the marrow cavities and lines the canals that pass through compact bone.

Contains both osteoblasts and osteoclasts.

haversian system
Haversian System

osteon

osteocyte

  • Osteon with central haversian canal containing
    • Cells
    • Vessels
    • Nerves
  • Volkmann’s canal
    • Connects osteons

Picture courtesy Gwen Childs, PhD.

Haversian canal

Volkmann’s canal

slide39
Spider-shaped osteocytes occupy small cavities known as lacunae at the junctions of the lamellae.

Hairlike canals called canaliculi connect the lacunae to each other and to the central canal.

Canaliculi allow the osteocytes to exchange nutrients, wastes, and chemical signals to each other via intercellular connections

another classification for types
Another Classification for -Types
  • Lamellar bone
      • Normal, mature, structured
  • Woven bone
      • Weak, fragile, immature, randomly organized
      • Ex
        • Bones in newborns
        • Fracture repair callus
        • Bone tumors
classification of bones cont n2
CLASSIFICATION of BONES cont’n.
  • According to location

A X I A L

skull 22

hyoid 1

ossicles 6

vertebrae 26

ribs & sternum 25_

80

classification of bones cont n3
CLASSIFICATION of BONES cont’n.
  • According to location

APPENDICULAR

Upper ExtremitiesLower Extremities

clavicle 2 hip bone 2

scapulae 2 femur 2

humerus 2 patella 2

radius 2 tibia 2

ulna 2 fibula 2

carpals 16 tarsals 14

metacarpals 10 metatarsals 10

phalanges 28__ phalanges 28__

64 62

blood supply
Blood Supply
  • Long bones have three blood supplies
    • Nutrient artery (intramedullary)
    • Periosteal vessels
    • Metaphyseal vessels

Periosteal

vessels

Nutrient

artery

Metaphyseal

vessels

Figure adapted from Rockwood and Green, 5th Ed

nutrient artery
Nutrient Artery
  • Normally the major blood supply for the diaphyseal cortex (80 to 85%)
  • Enters the long bone via a nutrient foramen
  • Forms medullary arteries up and down the bone
periosteal vessels
Periosteal Vessels
  • Arise from the capillary-rich periosteum
  • Supply outer 15 to 20% of cortex normally
  • Capable of supplying a much greater proportion of the cortex in the event of injury to the medullary blood supply
metaphyseal vessels
Metaphyseal Vessels
  • Arise from periarticular vessels
  • Penetrate the thin cortex in the metaphyseal region and anastomose with the medullary blood supply
bone marrow
Bone Marrow

soft tissue occupying the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger haversian canals.

There are 2 main types: red & yellow.

Red bone marrow = blood cell forming tissue = hematopoietic tissue

bone marrow1
Bone Marrow
  • Bone marrow is the spongy tissue in the cavities of the bones.
  • It is the blood cell ‘factory’ – it makes blood cells.
  • Healthy bone marrow releases blood cells into the blood stream when they are mature and when our body needs them.
    • The different blood cells made inside bone marrow are:
  • Red blood cells that carry oxygen around the body
  • Around 2.6 million red blood cells are produced each second by the bone marrow to replace those worn out and destroyed by the liver.
  • White blood cells that make up the body\'s immune system
      • Platelets which are needed for clotting.
  • Cancer of the blood is called…….
  • …leukaemia, where many more white blood cells are made than are needed. These cancerous white blood cells take over our blood!
bone remodeling steps
Bone Remodeling - Steps
  • (i) Resorption: stimulated osteoblast precursors release factors that induce osteoclast differentiation and activity. Osteoclasts remove bone mineral and matrix, creating an erosion cavity.
  • (ii) Reversal: mononuclear cells prepare bone surface for new osteoblasts to begin forming bone.
  • (iii) Formation: successive waves of osteoblasts synthesize an organic matrix to replace resorbed bone and fill the cavity with new bone.
  • (iv) Resting: bone surface is covered with flattened lining cells. A prolonged resting period follows with little cellular activity until a new remodelling cycle begins
axial skeleton
AXIAL SKELETON

I. SKULL

= skeleton --- head & face

= flattened & irregular

= united by joints (sutures)

cranium -- skull minus mandible

calvarium -- skull after the bones of the face have been removed

cavities: a. Cranial - contains the brain

b. Orbital - contains eyeball

& accessory organs

c. nasal

slide59

The skull

8 sutured bones in cranium

Facial bones: 13 sutured bones, 1 mandible

Cranium

encases brain

attachments for muscles

sinuses

anterior skull

frontal bone

glabella

supraorbital foramen

Anterior Skull

infraorbital foramen

zygomatic bone

mandibular symphysis

maxillary bone

alveolar fossa

mental foramen

mandible

sutures
Sutures

Sutures are the tight connections between skull bones

In the adult skull , the skull bones are unable to move or separate due to this tight connections

In infant skull this sutures are not well formed and the skull bones are mobile which facilitates the delivery of the baby

cranium
Cranium

frontal bone

coronal suture

parietal bone

sagittal suture

lambdoidal

suture

occipital bone

lateral skull
Lateral Skull

squamosal

suture

lacrimal

bone

temporal

bone

external acoustic

meatus

mandibular condyle

In mandibular fossa

(TMJ joint)

lateral skull1
Lateral Skull

zygomatic arch

sphenoid

bone

coronoid process

sutural bone

mastoid process

styloid process

ramus

angle

body

mandible

internal skull
Internal Skull

cribriform plate

crista galli

lesser wing

greater wing

optic canal

sella turcica

intenal acoustic meatus

jugular foramen

ventral skull
Ventral Skull

palatine process

sphenoid bone

palatine bone

vomer bone

styloid process

temporal bone

mastoid process

external occipital

protuberance

occipital bone

occipital bone
Occipital bone

carotid

canal

jugular

foramen

occipital

condyle

foramen magnum

divisions of the bones of the skull
Divisions of the bones of the skull
  • Cerebral / cranial bones / brain case (8 bones)

unpaired (4) paired (4)

1. occipital 1. parietal

2. frontal 2. temporal

3. sphenoid

4. ethmoid

b.Facial or visceral cranium

paired (12) unpaired (2)

a. Nasal a. Vomer

b. Lacrimal b. Mandible

c. Maxilla

d. Zygomatic / malar / cheek bones

e. Palatine

f. Inferior nasal concha or turbinate

frontal bone
Frontal bone

Forms the forehead

Roof of the orbit

articulates with parietal, sphenoid, lacrimal, nasal, ethmoid, zygomatic and maxilla

Contain 2 air filled cavities. ( frontal sinuses)

parietal bones
Parietal bones

Part of the superior and lateral surfaces of the cranium

-articulate with each other – sagittal suture

-articulate with occipital, frontal,

temporal and sphenoid bones

temporal bone
Temporal bone

Forms wall of jugular foramen

Associated with ear canal

Special parts

- zygomatic process

-forms cranial portion of the Tempero Mandibular joint

-inferior to zygo. process – mandibular fossa (mandibular condyle)

- inferior aspect – mastoid process

- inferior and medial to the MP – styloid process

occipital bone1
Occipital bone

Part of the base of the skull

articulates with parietal, temporal and sphenoid

Surrounds the foramen magnum

Occipital condyles articulate with Atlas – 1st cervical vertebra

slide80

The uppermost portion of the human respiratory system, the nose is a hollow air passage that functions in breathing and in the sense of smell. The nasal cavity moistens and warms incoming air, while small hairs and mucus filter out harmful particles and micro-organisms. This illustration depicts the interior of the human nose.

facial bones
Facial Bones

Nasal (2) Maxillae (2) Zygomatic (2)

Mandible (1) Lacrimal (2) Palatine (2)

Inferior nasal conchae (2) Vomer (1)

anterior skull1

frontal bone

glabella

supraorbital foramen

Anterior Skull

infraorbital foramen

zygomatic bone

mandibular symphysis

maxillary bone

alveolar fossa

mental foramen

mandible

sinuses
Sinuses

Frontal Sinus

Ethmoid Sinus

Sphenoid Sinus

Maxillary Sinus

  • Warm and moisten air
  • Lighten the skull
  • Enhance voice resonance
paranasal sinuses
Paranasal Sinuses

frontal sinus

ethmoid sinus

maxilary sinus

sphenoid sinus

fontanelles
Fontanelles

These are seen in new borns

At birth the junction between skull bones covered with a membrane

This allows the expansion and growth of the brain

Later they become ossified ( bone formation)

fontanelle
Fontanelle

= membrane filled spaces found in the skull of

newborn infants

e.g.: 1. anterior = largest

2. posterior

3. anterolateral (sphenoidal)

4. posterolateral (mastoid)

slide89

Allows for

growth

axial skeleton1
AXIAL SKELETON
  • HYOID BONE

= small U-shape; lies in front of the neck

= base of the tongue is attached

= lies between mandible & thyroid cartilage

II. OSSICLES

= small bones of the ear

a. Stapes (stirrup) 2

b. Incus (anvil) 2

c. Malleus (hammer) 2

hyoid
Hyoid +

external

acoustic

meatus

temmporal

mandibular

joint

Hyoid bone

mandible
Mandible

lower jaw carries teeth

only freely movable bone of the skull

moving articulations with temporal bone

bones forming the walls of the orbit
Bones forming the walls of the orbit

Roof - frontal

lesser wing of sphenoid

Medial wall – maxilla

lacrimal

ethmoid

sphenoid

Floor – maxilla

zygomatic

palatine

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