Unit 2: Skeletal Unit Framework of bones and cartilage that protects our organs and allows us to move

Functions of the Skeletal System Support- allow attachment of soft tissues and organsSupport- allow attachment of soft tissues and organs Protect vital components of bodyProtect vital components of body Ribs protect heart and lungsRibs protect heart and lungs Skull protects brainSkull protects brain

Functions of the Skeletal System Movement- change direction and magnitude of skeletal musclesMovement- change direction and magnitude of skeletal muscles Mineral storage- calcium and phosphorousMineral storage- calcium and phosphorous Hemopoiesis- red marrow produces red blood cells and other blood elementsHemopoiesis- red marrow produces red blood cells and other blood elements Vertebrae, sternum, scapula, humerus, femurVertebrae, sternum, scapula, humerus, femur

Bone Tissue Two types of bone tissue in skeletonTwo types of bone tissue in skeleton Compact- dense bone, solidCompact- dense bone, solid Spongy- lattice work structure spaces filled with marrowSpongy- lattice work structure spaces filled with marrow

Spongy Bone

Compact Bone

Types of Bone Bones are classified into four different categories according to their shape:Bones are classified into four different 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 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 boneCovered in thin layer or compact bone Examples: Wrist and ankle bonesExamples: Wrist and ankle bones

Types of Bones 3. Flat Bones3. Flat Bones Generally thin, consist of two parallel plates of compact bone enclosing a layer of spongy boneGenerally thin, consist of two parallel plates of compact bone enclosing a layer of spongy bone Give good protection (broad)Give good protection (broad) Large areas for muscle attachmentLarge areas for muscle attachment Examples: cranial bones, sternum, ribs, scapulasExamples: cranial bones, sternum, ribs, scapulas

Types of Bones 4. Irregular Bones4. Irregular Bones Complex shape that do not fit into any other categoryComplex shape that do not fit into any other category Vary in amount of compact and spongyVary in amount of compact and spongy Examples: Vertebrae and some facial bonesExamples: Vertebrae and some facial bones

Bone Tissue Four main types of cells makeup bone tissueFour main types of cells makeup bone tissue 1. Osteoprogenitor- undergo mitosis to become osteoblasts1. Osteoprogenitor- undergo mitosis to become osteoblasts 2. Osteoblasts- cells that form bone2. Osteoblasts- cells that form bone 3. Osteocytes- mature bones cells (osteoblasts become isolated in bony matrix)3. Osteocytes- mature bones cells (osteoblasts become isolated in bony matrix) 4. Osteoclasts- function in bone resorption, degradation4. Osteoclasts- function in bone resorption, degradation

Bone Tissue Matrix consists of mineral salts and collagen fibers 1. Mineral salts- mostly calcium, phosphate, and some calcium carbonate Salts deposited by osteoblasts in matrix, the tissue hardens and becomes calcified 2. Collagen fibers- makeup the framework of the matrix

Microscopic Anatomy of Compact Bone Concentric Ring StructureConcentric Ring Structure Central canal (haversian canal)- run lengthwise through bone; contain blood vessels and nervesCentral canal (haversian canal)- run lengthwise through bone; contain blood vessels and nerves

Concentric Ring Structure

Microscopic Anatomy of Compact Bone Lamellae- rings of hard, calcified matrix that are arranged concentrically around central canalLamellae- rings of hard, calcified matrix that are arranged concentrically around central canal Lacunae- small spaces between lamellae that contain osteocytesLacunae- small spaces between lamellae that contain osteocytes Canaliculi- outward extensions of osteocytes from lacunaeCanaliculi- outward extensions of osteocytes from lacunae Connect with other canaliculi from other lacunae and eventually with the central canalConnect with other canaliculi from other lacunae and eventually with the central canal Form a branching network throughout bone to provide numerous routes for nutrients and oxygen deliveryForm a branching network throughout bone to provide numerous routes for nutrients and oxygen delivery

Microscopic Anatomy of Compact Bone Haversian System- each central canal with its surrounding lamellae, lacunae, osteocytes, and canaliculi makeup an osteonHaversian System- each central canal with its surrounding lamellae, lacunae, osteocytes, and canaliculi makeup an osteon

Microscopic Anatomy of Spongy Bone 1. Irregular latticework structure1. Irregular latticework structure Trabeculae- thin plates of bone that makeup the latticework (No osteons)Trabeculae- thin plates of bone that makeup the latticework (No osteons) The spaces between the trabeculae of some bones are filled with red bone marrowThe spaces between the trabeculae of some bones are filled with red bone marrow Lacunae- contain osteocytes- nourished directly from the blood circulating through the marrow cavitiesLacunae- contain osteocytes- nourished directly from the blood circulating through the marrow cavities Spongy Bone

Parts of Long Bone 1. Diaphysis- the shaft or long, main portion of the bone1. Diaphysis- the shaft or long, main portion of the bone

Parts of a long bone 2. Epiphyses- the ends of the bone2. Epiphyses- the ends of the bone

Parts of a Long Bone 3. Articular cartilage- thin layer of cartilage covering the epiphyses where the bone forms a joint with another bone3. Articular cartilage- thin layer of cartilage covering the epiphyses where the bone forms a joint with another bone Cartilage reduces friction and absorbs shockCartilage reduces friction and absorbs shock

Parts of a Long Bone

4. Peristoneum- dense, white, fibrous covering around the surface of the bone not covered by cartilage4. Peristoneum- dense, white, fibrous covering around the surface of the bone not covered by cartilage Outer layer contains blood vessels and nerves that pass into the boneOuter layer contains blood vessels and nerves that pass into the bone Inner layer contains osteoblasts and osteoclastsInner layer contains osteoblasts and osteoclasts Plays role in protection, nutrition, growth, and repairPlays role in protection, nutrition, growth, and repair Site of attachment for ligaments and tendonsSite of attachment for ligaments and tendons

Parts of a Long Bone

Medullary (marrow) cavity- space within the diaphysis that contains the yellow marrow (fatty) in adultsMedullary (marrow) cavity- space within the diaphysis that contains the yellow marrow (fatty) in adults Yellow marrow functions in energy storageYellow marrow functions in energy storage

Parts of a Long Bone

Endosteum- lining of the medullary cavityEndosteum- lining of the medullary cavity

Bone Formation 1. Primary ossification center- located at the center of the diaphysis A. Cartilage cells degenerate and are replaced by osteoblasts B. Osteoblasts produce bone around the primary ossification center, expanding towards epiphyses C. Osteoclasts break down bone in the middle and produce the medullary cavity D. Cartilage continues to grow at its ends, increasing length

2. Secondary ossification centers- located at the epiphyses2. Secondary ossification centers- located at the epiphyses A. Produce spongy boneA. Produce spongy bone B. Bone tissue completely replaces cartilage (except for 2 regions)B. Bone tissue completely replaces cartilage (except for 2 regions) 1. cartilage continues to cover the articular surfaces of the epiphyses1. cartilage continues to cover the articular surfaces of the epiphyses 2. cartilage remains in a region between the epiphyses and diaphysis = epiphyseal plate2. cartilage remains in a region between the epiphyses and diaphysis = epiphyseal plate Allows diaphysis to increase in lengthAllows diaphysis to increase in length Formation

Bone Remodeling Bone continually replaces itself throughout the adult lifeBone continually replaces itself throughout the adult life Remodeling- the replacement of old bone tissue with new bone tissueRemodeling- the replacement of old bone tissue with new bone tissue Compact bone is formed by the transformation of spongy boneCompact bone is formed by the transformation of spongy bone The diameter of long bone is increased by destruction of bone internally and construction of new bone externallyThe diameter of long bone is increased by destruction of bone internally and construction of new bone externally Fractures