Unit 2: Skeletal UnitUnit 2: Skeletal Unit

Framework of bones and Framework of bones and cartilage that protects our cartilage that protects our

organs and allows us to moveorgans and allows us to move

Functions of the Skeletal Functions of the Skeletal SystemSystem

• Support- allow attachment of soft Support- allow attachment of soft tissues and organstissues and organs

• Protect vital components of body Protect vital components of body • Ribs protect heart and lungsRibs protect heart and lungs• Skull protects brainSkull protects brain

Functions of the Skeletal Functions of the Skeletal SystemSystem

• Movement- change direction and Movement- change direction and magnitude of skeletal musclesmagnitude of skeletal muscles

• Mineral storage- calcium and Mineral storage- calcium and phosphorousphosphorous

• Hemopoiesis- red marrow Hemopoiesis- red marrow produces red blood cells and other produces red blood cells and other blood elementsblood elements• Vertebrae, sternum, scapula, Vertebrae, sternum, scapula,

humerus, femurhumerus, femur

Bone TissueBone Tissue

• Two types of bone tissue in Two types of bone tissue in skeletonskeleton• Compact- dense bone, solidCompact- dense bone, solid• Spongy- lattice work structure spaces Spongy- lattice work structure spaces

filled with marrowfilled with marrow

Spongy Bone

Spongy Bone

Spongy Bone Compact Bone

Types of BoneTypes of Bone

• Bones are classified into four different Bones are classified into four different categories according to their shape:categories according to their shape:• 1. Long Bones1. Long Bones

• Greater length than widthGreater length than width• Slightly curved for strengthSlightly curved for strength• Consist mostly of compact (dense) bone tissueConsist mostly of compact (dense) bone tissue• Also contain spongy tissueAlso contain spongy tissue• Examples: Arm, thigh bones, fingers, and toesExamples: Arm, thigh bones, fingers, and toes

Types of BonesTypes of Bones

• 2. Short Bones2. Short Bones• Equal length and width (cube-shaped)Equal length and width (cube-shaped)• Consist mostly of spongy boneConsist mostly of spongy bone• Covered in thin layer or compact Covered in thin layer or compact

bonebone• Examples: Wrist and ankle bonesExamples: Wrist and ankle bones

Types of BonesTypes of Bones

• 3. Flat Bones3. Flat Bones• Generally thin, consist of two parallel Generally thin, consist of two parallel

plates of compact bone enclosing a plates of compact bone enclosing a layer of spongy bonelayer of spongy bone

• Give good protection (broad)Give good protection (broad)• Large areas for muscle attachmentLarge areas for muscle attachment• Examples: cranial bones, sternum, Examples: cranial bones, sternum,

ribs, scapulasribs, scapulas

Types of BonesTypes of Bones

• 4. Irregular Bones4. Irregular Bones• Complex shape that do not fit into Complex shape that do not fit into

any other categoryany other category• Vary in amount of compact and Vary in amount of compact and

spongyspongy• Examples: Vertebrae and some facial Examples: Vertebrae and some facial

bonesbones

Bone TissueBone Tissue

• Four main types of cells makeup bone Four main types of cells makeup bone tissuetissue• 1. Osteoprogenitor- undergo mitosis to 1. Osteoprogenitor- undergo mitosis to

become osteoblastsbecome osteoblasts• 2. Osteoblasts- cells that form bone2. Osteoblasts- cells that form bone• 3. Osteocytes- mature bones cells 3. Osteocytes- mature bones cells

(osteoblasts become isolated in bony (osteoblasts become isolated in bony matrix)matrix)

• 4. Osteoclasts- function in bone resorption, 4. Osteoclasts- function in bone resorption, degradationdegradation

Bone TissueBone Tissue

• Matrix consists of mineral salts and Matrix consists of mineral salts and collagen fiberscollagen fibers• 1. Mineral salts- mostly calcium, 1. Mineral salts- mostly calcium,

phosphate, and some calcium phosphate, and some calcium carbonatecarbonate

• Salts deposited by osteoblasts in matrix, Salts deposited by osteoblasts in matrix, the tissue hardens and becomes calcifiedthe tissue hardens and becomes calcified

• 2. Collagen fibers- makeup the 2. Collagen fibers- makeup the framework of the matrixframework of the matrix

Microscopic Anatomy of Microscopic Anatomy of Compact BoneCompact Bone

• Concentric Ring StructureConcentric Ring Structure• Central canal (haversian canal)- run Central canal (haversian canal)- run

lengthwise through bone; contain lengthwise through bone; contain blood vessels and nervesblood vessels and nerves

Concentric Ring Structure

Microscopic Anatomy of Microscopic Anatomy of Compact BoneCompact Bone

• Lamellae- rings of hard, calcified matrix that Lamellae- rings of hard, calcified matrix that are arranged concentrically around central are arranged concentrically around central canalcanal

• Lacunae- small spaces between lamellae that Lacunae- small spaces between lamellae that contain osteocytescontain osteocytes

• Canaliculi- outward extensions of osteocytes Canaliculi- outward extensions of osteocytes from lacunaefrom lacunae

• Connect with other canaliculi from other lacunae and Connect with other canaliculi from other lacunae and eventually with the central canaleventually with the central canal

• Form a branching network throughout bone to Form a branching network throughout bone to provide numerous routes for nutrients and oxygen provide numerous routes for nutrients and oxygen deliverydelivery

Microscopic Anatomy of Microscopic Anatomy of Compact BoneCompact Bone

• Haversian System- each central Haversian System- each central canal with its surrounding canal with its surrounding lamellae, lacunae, osteocytes, and lamellae, lacunae, osteocytes, and canaliculi makeup an osteoncanaliculi makeup an osteon

Microscopic Anatomy of Microscopic Anatomy of Spongy BoneSpongy Bone

• 1. Irregular latticework structure1. Irregular latticework structure• Trabeculae- thin plates of bone that Trabeculae- thin plates of bone that

makeup the latticework (No osteons)makeup the latticework (No osteons)• The spaces between the trabeculae of The spaces between the trabeculae of

some bones are filled with red bone some bones are filled with red bone marrowmarrow

• Lacunae- contain osteocytes- Lacunae- contain osteocytes- nourished directly from the blood nourished directly from the blood circulating through the marrow cavitiescirculating through the marrow cavities

Spongy Bone

Parts of Long BoneParts of Long Bone

• 1. Diaphysis- the shaft or long, 1. Diaphysis- the shaft or long, main portion of the bonemain portion of the bone

Parts of a long boneParts of a long bone

• 2. Epiphyses- the ends of the bone2. Epiphyses- the ends of the bone

Parts of a Long BoneParts of a Long Bone

• 3. Articular cartilage- thin layer of 3. Articular cartilage- thin layer of cartilage covering the epiphyses cartilage covering the epiphyses where the bone forms a joint with where the bone forms a joint with another boneanother bone• Cartilage reduces friction and absorbs Cartilage reduces friction and absorbs

shockshock

Parts of a Long BoneParts of a Long Bone

Parts of a Long BoneParts of a Long Bone

• 4. Peristoneum- dense, white, fibrous 4. Peristoneum- dense, white, fibrous covering around the surface of the bone covering around the surface of the bone not covered by cartilagenot covered by cartilage• Outer layer contains blood vessels and nerves Outer layer contains blood vessels and nerves

that pass into the bonethat pass into the bone• Inner layer contains osteoblasts and Inner layer contains osteoblasts and

osteoclastsosteoclasts• Plays role in protection, nutrition, growth, and Plays role in protection, nutrition, growth, and

repairrepair• Site of attachment for ligaments and tendonsSite of attachment for ligaments and tendons

Parts of a Long BoneParts of a Long Bone

Parts of a Long BoneParts of a Long Bone

Parts of a Long BoneParts of a Long Bone

• Medullary (marrow) cavity- space Medullary (marrow) cavity- space within the diaphysis that contains within the diaphysis that contains the yellow marrow (fatty) in adultsthe yellow marrow (fatty) in adults• Yellow marrow functions in energy Yellow marrow functions in energy

storagestorage

Parts of a Long BoneParts of a Long Bone

Parts of a Long BoneParts of a Long Bone

• Endosteum- lining of the medullary Endosteum- lining of the medullary cavitycavity

Bone FormationBone Formation

• 1. Primary ossification center- located 1. Primary ossification center- located at the center of the diaphysisat the center of the diaphysis• A. Cartilage cells degenerate and are A. Cartilage cells degenerate and are

replaced by osteoblastsreplaced by osteoblasts• B. Osteoblasts produce bone around the B. Osteoblasts produce bone around the

primary ossification center, expanding primary ossification center, expanding towards epiphysestowards epiphyses

• C. Osteoclasts break down bone in the C. Osteoclasts break down bone in the middle and produce the medullary cavitymiddle and produce the medullary cavity

• D. Cartilage continues to grow at its ends, D. Cartilage continues to grow at its ends, increasing lengthincreasing length

Bone FormationBone Formation

• 2. Secondary ossification centers- 2. Secondary ossification centers- located at the epiphyseslocated at the epiphyses• A. Produce spongy boneA. Produce spongy bone• B. Bone tissue completely replaces B. Bone tissue completely replaces

cartilage (except for 2 regions)cartilage (except for 2 regions)• 1. cartilage continues to cover the articular 1. cartilage continues to cover the articular

surfaces of the epiphysessurfaces of the epiphyses• 2. cartilage remains in a region between 2. cartilage remains in a region between

the epiphyses and diaphysis = epiphyseal the epiphyses and diaphysis = epiphyseal plateplate

• Allows diaphysis to increase in lengthAllows diaphysis to increase in lengthFormation Formation

Bone RemodelingBone Remodeling

• Bone continually replaces itself Bone continually replaces itself throughout the adult lifethroughout the adult life

• Remodeling- the replacement of old Remodeling- the replacement of old bone tissue with new bone tissuebone tissue with new bone tissue

• Compact bone is formed by the Compact bone is formed by the transformation of spongy bonetransformation of spongy bone

• The diameter of long bone is increased The diameter of long bone is increased by destruction of bone internally and by destruction of bone internally and construction of new bone externallyconstruction of new bone externally

Fractures