Musculoskeletal System PDF

MUSCULOSKELETAL SYSTEM Dr. Nehemiah B. Mula SKELETAL SYSTEM There are 206 bones in the body Functions of the Skeletal System ○ Body support ○ Organ protection ○ Body movement ○ Mineral storage ○ Blood Cell production BONE HISTOLOGY Bon...

MUSCULOSKELETAL SYSTEM Dr. Nehemiah B. Mula SKELETAL SYSTEM There are 206 bones in the body Functions of the Skeletal System ○ Body support ○ Organ protection ○ Body movement ○ Mineral storage ○ Blood Cell production BONE HISTOLOGY Bone Matrix ○ 35% organic Collagen and proteoglycans ○ 65% inorganic Calcium phosphate crystals called hydroxyapatite ○ Balance should be maintained between the organic and inorganic component Too much collagen → bone becomes too flexible Too much mineral → brittle bone BONE CELLS 3 types of bone cells ○ Osteoblasts Bone-building cells Produce collagen and proteoglycan Secrete matrix vesicle which contains high concentration of Calcium and Phosphate → Hydroxyapatite crystals Participate in bone formation called Ossification BONE CELLS 3 types of bone cells ○ Osteocytes Bone cells trapped in the cellular matrix Housed in spaces called lacunae Accounts for 90-95% of bone cells ○ Osteoclasts Bone-destroying cells Active in bone resorption Woven and Lamellar Bone Woven Bone ○ First type of bone that osteoblasts form during ossification ○ Weak; collagen fibers are randomly oriented in many directions ○ Broken down by osteoclasts to form a stronger, more permanent bone structure Lamellar Bone ○ Mature bone; organized into thin, concentric sheets or layers called lamellae ○ Collagen fibers are arranged in a more organized manner Spongy and Compact Bone Spongy Bone (Cancellous bone) ○ Consist of interconnecting rods or plates of bone called trabeculae ○ has a porous, honeycomb-like structure that is filled with marrow ○ Between the trabeculae are spaces filled with red bone marrow (for blood production) ○ Found in flat bones (skull, sternum, ribs) Compact Bone ○ Solid, outer layer surrounding each bone ○ Has more matrix and is denser with fewer pores than spongy bone ○ Has a functional unit called osteon or haversian system Classification of Bones according to shape Long Bones ○ Bones that are longer than wide ○ Consist of a shaft, diaphysis, epiphysis ○ Humerus, femur, radius, ulna Short Bones ○ Roughly cube-shaped bones composed mainly of spongy bone ○ Carpals (wrist), tarsals (ankle) Flat Bones ○ Contain an interior framework of spongy bone sandwiched between 2 layers of compact bone ○ Sternum, skull, ribs Classification of Bones according to shape Irregular Bones ○ Has a peculiar or differing shapes ○ Vertebrae, ossicles of the ears Sesamoid Bones ○ Enclosed in tendon and fascia ○ Found adjacent to joints ○ Patella (kneecap) Structure of Long Bones Diaphysis ○ Center portion of the bone ○ Composed primarily of of compact bone, surrounding a hollow center called medullary cavity ○ Primary ossification center (site where bones develop from) Epiphysis ○ Ends of long bones ○ Mostly spongy bone with an outer layer of compact bone ○ Long bones of the arm, forearm, and thigh has one or more epiphysis ○ Long bones of hands and foot has one epiphysis only Structure of Long Bones Epiphyseal Plate ○ Also known as growth plate ○ Located between the epiphysis and diaphysis ○ Where growth in length takes place Red and Yellow Marrow ○ Red marrow Connective tissue in the spaces of spongy bone or in the medullary cavity Site of blood cell production ○ Yellow marrow Fat stored within the medullary cavity Structure of Long Bones Periosteum ○ Connective tissue membrane covering the outer surface of a bone ○ Has 2 layers: Outer layer is made up of dense irregular collagenous connective tissue containing blood vessels and nerves Inner layer is a single layer of bone cells Endosteum ○ Single layer of tissue covering the internal surfaces of all cavities within bones Parts of the Long Bone Bone Development Bone formation in the fetus follows two patterns: ○ Intramembranous Ossification Bone formation starts within embryonic connective tissue membranes ○ Endochondral Ossification Starts with a cartilage model  Intramembranous Ossification Ossification starts from embryonic mesenchyme membrane Seen in the skull bones, part of mandible, diaphysis of clavicle Centers of Ossification ○ Where intramembranous ossification begins ○ Expand to form a bone by gradually ossifying the membrane Endochondral Ossification Begins with the formation of a cartilage model Seen in the bones of the base of the skull, parts of the mandible, epiphyses of the clavicle, and most of the remaining skeletal system develop through endochondral ossification Endochondral and Intramembranous Ossification Bone Growth Growth in Bone Length ○ Long bones and bony projections increase in length because of growth at the epiphyseal plate. ○ Grow by creating new cartilage in the epiphyseal plate ○ New cartilage calcifies and ossifies following the same process of endochondral ossification Growth in Bone Width ○ Long bones increases in diameter because of the appositional bone growth beneath the periosteum ○ Osteoblasts from the periosteum lay down bone under the periosteum which gradually increases the amount of bone surrounding the medullary cavity and overall thickness of the bone Bone Remodelling Process where old bone is replaced with new bone Osteoclast removes old bone and osteoblast deposit new bone Converts woven bone into lamellar bone Basic Multicellular Unit ○ Temporary assembly of osteoclast and osteoblast that travels through or across the surface of the bone ○ Remove old bone matrix and replace it with new bone matrix Overview of the Bones in the Body 206 bones in an adult human body Bones are segregated into the axial and appendicular skeleton ○ Axial Skeleton Skull, ear ossicles, hyoid bone, vertebral column, thoracic cage ○ Appendicular Skeleton Consists of the bones of the upper and lower limbs and the two girdles (pectoral and pelvic) The girdles are zones where limbs are attached to the body  CRANIAL BONES FACIAL BONES PAIRED UNPAIRED PAIRED UNPAIRED Parietal Frontal Palatine Vomer Temporal Occipital Lacrimal Mandible Sphenoid Maxilla Ethmoid Nasal Inferior nasal concha Zygomatic Bone Fractures Fracture is a break or disruption in the continuity of the bone or disruption of the architecture of the bone May result from a trauma or pathologic disease of the bone May be open or closed fracture Can be classified as displaced or non-displaced Transverse Fracture Fracture runs horizontally Spiral Fracture Helical fracture from twisting of the bone Comminuted Bone is broken into at least 3 fragments Greenstick Fracture with break on one side and bent on the other Thank you! 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