HPP Lab - The Skeletal System PDF

The Skeletal System Keith Jane Olanda Perez, RPh Human Physiology and Pathophysiology Laboratory CONTENTS: Introduction Bone Gross Joints Ossification Anatomy Skeletal System Functions of Skeletal System: 1. Support...

The Skeletal System Keith Jane Olanda Perez, RPh Human Physiology and Pathophysiology Laboratory CONTENTS: Introduction Bone Gross Joints Ossification Anatomy Skeletal System Functions of Skeletal System: 1. Support a. Strong bone and firm, flexible cartilage provide support 2. Protection a. Bone is hard and protects organs 3. Movement a. Allow movement 4. Storage a. Calcium and phosphorous are stored in bone b. Adipose tissue is stored within bone cavities 5. Blood Cell Production a. Bone cavities are filled with red bone marrow i. Red bone marrow produces blood cells and platelets Components of Skeletal System: Bone Extracellular Matrix (self repair → metabolically active, lots of (differentiates components of skeletal blood/nutrients) system) Bone: Cartilage Collagen & minerals (can be easily destroyed by obesity → lots Flexible, able to bear weight of pressure on knee) Reduce friction → cushion Cartilage: Model for bone formation Collagen & proteoglycans Cartilage can't repair itself well Good shock absorber Tendons Tendons & Ligaments Attach muscle to bone Extracellular matrix is collagen Very strong and tough Ligaments Attach bone to bone CANNOT repair itself Skeletal System Features of Bone : Long bones → longer than they are wide Bones of upper and lower limbs (femur, tibia, fibula) Short bones → as wide as they are long Wrist and ankle bones (carpals, tarsals, phalanges) Flat bones → thin, flat shape Certain skull bones, ribs, scapulae, and sternum Ribs, sternum, skull Irregular bones → shapes that do not fit readily into the other 3 categories Vertebrae, facial bone, Sphenoid bone Skeletal System  Structure of Long Bone : ○ Epiphyseal Plate (growth plate): site of growth between diaphysis and epiphysis ○ Epiphysis: end of a bone; separated from Epiphyseal plate → indicates the remainder of the bone by the juvenile (young) epiphyseal plate/line Epiphyseal line → indicates ○ Each long bone consists of a older bone (plate is fused) central shaft and two ends Puberty → steroid hormones ○ Thin layer of articular cartilage are responsible for fusing the covers ends of epiphysis where bone joints epiphyseal plate → fusing the plate with other bones stops growth!! When bone growth stops, epiphyseal plate is replaced by bone and becomes an epiphyseal line! Skeletal System Structure of Long Bone : Diaphysis: central shaft of a long bone Open space in middle → Medullary Cavity Medullary Cavity: large, marrow-filled cavity in the diaphysis of long bone ○ Cavities in bone are filled with marrow: Yellow marrow → consists of adipose tissue Red marrow→ consists of blood-forming cells and is the only site of blood formation in adults Children have more red marrow in their bones than adult bones As one ages, red marrow is replaced by yellow marrow In adults, red marrow is confined to bones of central axis of body and most proximal epiphyses of limbs Skeletal System  Structure of Long Bone : Periosteum: membrane around bone's outer ○Bone is formed in thin sheets of surface extracellular matrix known as Contains blood vessels and nerves → vascular Lamellae (thin sheet/layer of bone) Has 2 layers: ○ Inner layer of Periosteum: ○Osteocytes are located between the Attach bone lamellae within spaces known as ○Outer layer of Periosteum: Lacunae Blood vessels Endosteum: lines medullary cavity ○Cell processes extend from the Periosteum and endosteum both contain osteocytes across the extracellular osteoblasts matrix of the lamellae within tiny Osteoblasts: bone-making cells; can divide canals called Canaliculi Turn into osteocytes Osteocytes: mature bone cell surrounded by bone matrix; maintain bone matrix Osteoclasts: remodel bone Skeletal System Skeletal System Skeletal System Flat Bone Compact Bone Located in outer part of diaphysis (long bones) Lamella: rings of bone matrix and thinner surfaces of other bones ○ Osteons: structural unit of compact bone; Lacunae: spaces between lamella, single central canal with its contents and the filled w/ Osteocytes associated lamellae and osteocytes surrounding it Canaliculus: tiny canals built by Each osteon has concentric rings of Osteocytes, transport nutrients and lamellae surrounding a central canal waste into central canal Nutrients leave the blood vessels of central canal and diffuse to osteocytes via the Central Canal: center of osteon canaliculi Waste products diffuse in the opposite direction! Skeletal System Flat Bone Spongy Bone ○ NO OSTEONS ○ Located in epiphyses of long bones and center of other bones ○ Trabeculae: interconnecting rods, spaces contain marrow No central canal! Add strength to a bone without adding weight since it's not forming a solid, mineralized matrix Spaces in between trabeculae are filled with marrow ○ Each trabecula consists of several lamellae w/ osteocytes between them No blood vessels penetrate trabeculae ○ Nutrients exit vessels in marrow and pass by diffusion through canaliculi to osteocytes of trabeculae Skeletal System Skeletal System Bone Ossification Skeletal System Bone Ossification Ossification: formation of bone by osteoblasts After osteoblast is fully surrounded by bone matrix, it becomes osteocyte ○ Ossification Center: where bone formation begins ○ Primary Ossification Center: where bone first begins to appear Forms diaphyses ○ Secondary Ossification Center: forms epiphyses Bone Ossification Intramembranous Ossification → bone formation inside connective tissue membranes Osteoblasts build bone ○ Occurs in skull bones Skeletal System Skeletal System Bone Ossification Endochondral Ossification → bone formation inside cartilage Occurs in all bones (except skull) Cartilage models are replaced by bone Steps in Endochondral Ossification: 1. Chondroblasts build a cartilage model, the chondroblasts become chondrocytes 2. Cartilage model calcifies (hardens) 3. Osteoblasts invade calcified cartilage, primary ossification center forms diaphysis 4. Secondary ossification centers form epiphysis 5. Original cartilage model is almost completely ossified and remaining cartilage is articular cartilage Skeletal System Skeletal System Skeletal System Skeletal System  Bone Growth ○ Infancy and youth: Long bones lengthen at epiphyseal plate Long bones widen by adding more lamella → Appositional Growth ○ End of bone growth (in length): Epiphyseal plate is replaced by epiphyseal line Skeletal System Bone Remodeling ○Removal of existing bone by osteoclasts, deposition of new bone by osteoblasts ○Occurs in all bone, normal process ○Remodeling is responsible for: Change in bone shape Adjustment of bone to stress i.e. Astronauts lose strength in bone → Osteoporosis ○ No force on bones Bone repair Calcium ion regulation Calcium is removed from bones when blood calcium levels decrease Calcium is deposited when dietary calcium is adequate Both removal and deposition are under hormonal control ○ If too much is deposited, bones become thick or have abnormal lumps that can interfere w/ normal function ○ If too little is deposited, bones weaken and become susceptible to fracture → Osteoporosis Skeletal System Skeletal System Bone Repair 1. Broken bone causes bleeding and a blood clot (hematoma) forms 2. Callus forms, which is fibrous network between 2 fragments 3. Cartilage model forms first a. Then, osteoblasts enter the callus and form cancellous bone (spongy bone) for 4-6 weeks after injury 4. Cancellous bone (spongy bone) is slowly remodeled Skeletal System Skeletal System Skeletal System Hematopoietic Tissue ○ Makes blood cells Red blood cells White blood cells ○ Red marrow → location of blood-forming cells ○ Yellow marrow → mostly fat ○ Location of Hematopoietic tissue in newborns : Most bones (red marrow) ○ Location of Hematopoietic tissue in adults: Red is replaced with yellow marrow Red marrow is mainly in epiphyses of femur and humerus now Skeletal System Calcium Homeostasis ○ Bone is major storage site for calcium Movement of calcium into/out of bone helps determine blood calcium levels Necessary for normal muscle and nervous system function Calcium moves into bone as osteoblasts build new bone Calcium moves out of bone as osteoclasts break down bone ○ When blood calcium levels are too low, osteoclast activity increases Osteoclasts release calcium from bone into blood to increase blood calcium levels ○ When blood calcium levels are too high, osteoclast activity decreases Osteoblasts remove calcium from blood to produce new bone to decrease blood calcium levels Calcium homeostasis is maintained by 3 hormones: ○ Parathyroid Hormone (PTH) from parathyroid glands ○ Vitamin D from skin/diet Both PTH and vitamin D are secreted when blood calcium levels are too low Decreasing blood calcium levels will stimulate PTH secretion ○ Calcitonin from thyroid gland Secreted when blood calcium levels are too high Skeletal System Skeletal System Calcium Homeostasis ○ Parathyroid Hormone (PTH): ○ Indirectly stimulates osteoclasts to break down bone, which releases stored calcium into blood ○ Stimulates kidney to take up calcium from urine and return it to blood ○ Stimulates formation of active vitamin D, which promotes increases calcium absorption from small intestine ○ Calcitonin: ○ Works to decrease blood calcium levels by inhibiting osteoclast activity In the absence of osteoclast activity, osteoblast activity still continues (osteoblasts continue to remove calcium of blood and deposit into bone) Skeletal System Effects of aging on the Skeletal Syste m 1. With aging, bone matrix is lost and the matrix becomes more brittle. 2. Spongy bone loss results from thinning and loss of trabeculae. Compact bone loss mainly occurs from the inner surface of bones and involves formation of fewer osteons. 3. Loss of bone increases the risk for fractures and causes deformity, loss of height, pain, stiffness, and loss of teeth. 4. Exercise and dietary supplements are effective at preventing bone loss. Skeletal System Skeletal System Gross Anatomy Gross Anatomy Gross Anatomy Considerations of Bone Anatomy Axial Skeleton Consists of: skull, vertebra, thoracic cage Skull ○Frontal bone of skull forms majority of anterior cranial fossa ○ Occipital bone of skull forms majority of posterior cranial fossa ○ Styloid process: attachment site for tongue ○ Mandibular fossa: depression where lower jaw and skull meet ○ Glenoid fossa: where humerus meets scapula ○ Sphenoid bone → location of many foramen for cranial nerves ○ Foramen Ovale ○ Anosmia → shearing of axon with head blow → loss of smell ○ Axons can regenerate ○ Hard palate: roof of mouth ○ Palatine bones are in back of hard palate ○ Mandible: lower jaw, moves ○ Maxilla: upper jaw, doesn’t move Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Considerations of Bone Anatomy Axial Skeleton Consists of: skull, vertebra, thoracic cage ○Vertebral column ○ 7 cervical ○ 12 thoracic ○ 5 lumbar ○ 1 sacrum (5 fused sacral vertebrae) ○ 1 coccyx ○ Atlas → 1st vertebra, holds the head ○ Axis → 2nd vertebra, rotates head ○ Functions of Vertebral column: Support Protect spinal cord Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Considerations of Bone Anatomy Axial Skeleton Consists of: skull, vertebra, thoracic cage Thoracic cage ○ Protects vital organs ○ 12 pairs of ribs ○ Sternum: breastbone ○ True ribs: attach directly to sternum by cartilage (1-7) ○ False ribs: attach indirectly to sternum by cartilage (8-12) ○ Floating ribs: not attached to sternum Gross Anatomy Considerations of Bone Anatomy Appendicular Skeleton Consists of bones of upper limb and lower limb, pectoral girdle, pelvic girdle Pectoral Girdle Scapula Clavicle Upper Limb Bones Humerus Ulna Radius (outer bone of forearm) Carpals (wrist) Metacarpals (hand) Phalanges (fingers) Gross Anatomy Gross Anatomy Gross Anatomy  Considerations of Bone Anatomy Appendicular Skeleton Pelvic Girdle Pelvis: pelvic girdle + coccyx ○ Shaped differently for men and women (adaptation for childbirth) Ischium: inferior and posterior region Ilium: most superior region Acetabulum: hip socket (joint) Lower Limb Bones Femur → largest bone in body (strongest, too) Patella Tibia Fibula Tarsals (ankle) → 7 tarsal bones Metatarsals (foot) Phalanges (toes and fingers) Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Gross Anatomy Joints  Joints Joints ○ Synarthrosis: non-movable joint e.g. Skull ○ Amphiarthrosis: slightly movable joint e.g. between vertebrae ○ Diarthrosis: freely movable joint e.g. Knee, Elbow, Wrist  Joints Fibrous joints ○ 2 bones united by fibrous tissue → little to no movement Sutures Fibrous joint between flat bones of skull In newborns, some parts of sutures are wide and are called fontanels (soft spots) → allow flexibility during birth process and growth of head after birth Syndesmoses Fibrous joint in which bones are separated by some distance and held together by ligaments ○ e.g. fibrous membrane connecting radius and ulna Gomphoses Pegs fitted into sockets, held in place by ligaments ○ e.g. joint between tooth and its socket Joints Joints  Joints Cartilaginous joints Synchondroses A synchondrosis consists of two bones joined ○ Unites 2 bones via cartilage → slight by hyaline cartilage where little or no movement movement occurs. e.g. cartilage at epiphyseal plates of growing long bones e.g. cartilage between ribs and sternum Symphyses ○ Cartilage can be reinforced by A symphysis consists of fibrocartilage uniting additional collagen fibers in cartilaginous two bones. joints where lots of stress is placed on the Some of these joints are slightly joint movable because of the somewhat flexible Forms a type of cartilage: nature of fibrocartilage. Fibrocartilage Joints  Joints Features of a synovial jointscartilage → covers articular surfaces of Articular bones within synovial joints Synovial joints Provides smooth surface where bones meet ○ Freely moveable joints Joint cavity → filled with fluid, enclosed by joint Contain fluid in a cavity capsule surrounding ends of articulating Joint capsule → hold bones together, allows bones movement Synovial membrane → lines joint cavity ○ Joints that unite bones of appendicular everywhere, except over articular cartilage skeleton are mostly synovial joints May extend as a pocket/sac known as a (Most in axial skeleton are not bursa between structures exposed to rubbing → less mobile than appendicular together skeleton) May extend as a tendon sheath along some tendons associated w/ joints Synovial membrane produces synovial fluid (mixture of polysaccharides, proteins, lipids, and cells) Joints  Joints Types of Synovial ○ PlaneJoints joint, or gliding joint, consists of two flat bone surfaces of about equal ○ Pivot joint is a uniaxial joint that restricts size between which a slight gliding movement to rotation around a single axis motion can occur ○ Ball-and-socket joint consists of a ball (head) at ○ Saddle joint consists of two saddle- the end of one bone and a socket in an adjacent shaped articulating surfaces oriented at bone into which a portion of the ball fits. This type right angles to each other so that their of joint is multiaxial, allowing a wide range of complementary surfaces articulate. movement in almost any direction. Saddle joints are biaxial joints ○ Ellipsoid joint (condyloid joint) is a modified ○ Hinge joint is a uniaxial joint in which ball-andsocket joint a convex cylinder in one bone is applied to a corresponding concavity in the other bone Joints  1. Gliding movements occur when two flat Joints surfaces glide over one another. 2. Angular movements include flexion and Types of Movement: extension, plantar flexion and dorsiflexion, ○ Flexion: bending and abduction and adduction. ○ Extension: straightening ○ Abduction: movement AWAY from 3. Circular movements include rotation, the midline pronation and supination, and ○ Adduction: movement TOWARD circumduction. midline ○ Pronation: rotation of forearm with 4. Special movements include elevation and palms down depression, protraction and retraction, ○ Supination: rotation of forearm excursion, opposition and reposition, and with palms up inversion and eversion. ○ Rotation: movement of structure about long axis 5. Combination movements involve two or more of the previously mentioned movements. Joints Joints Joints Joints Joints Joints Joints Joints  Joints Effects of aging on the Joints 1. With age, the connective tissue of the joints becomes less flexible and less elastic. The resulting joint rigidity increases the rate of wear in the articulating surfaces. The changes in connective tissue also reduce the range of motion. 2. The effects of aging on the joints can be slowed by exercising regularly and consuming a healthy diet. Thank You!