PSIO Lecture Exam 2

MEOW

Hemopoeisis

Hemopoeisis

red and white blood cell formation in red marrow

Endosteum

lines inner surface of bone such as marrow cavity, contains osteogenic cells

Periosteum

membrane covering external surface of bone, two layers

Epiphysis

round structure at end of long bones, contains epiphyseal plate

Metaphysis

Area below epiphysis

Types of bones

long, short, flat, irregular, sesamoid, sutural

Types of joints (structure)

fibrous, cartilaginous, synovial

Fibrous joint

contains dense irregular CT between bones

Cartilaginous joint

contains hyaline cartilage in between bones

Synovial joint

contains synovial fluid in between bones

Types of joints (function)

synarthrosis, diarthrosis, amphiarthrosis

Synarthrosis Joint

Immovable joint, either fibrous or cartilaginous

Amphiarthrosis Joint

Slightly movable joint, either fibrous or cartilaginous

Diarthrosis Joint

Freely movable joint, always synovial, i.e. gliding, pivot, hinge, condyloid, saddle, ball and socket

Synovial fluid

Lubricates joints, provides nutrients to articular cartilage, absorbs shock

Accessory structures of synovial joints

Bursae (fluid filled sacs), menisci (articular discs), ligaments, tendons

Arthritis

Two types: osteoarthritis which is degenerative, and rheumatoid which is inflammatory

Glenohumeral Joint

Shoulder joint, tri-axial, ball and socket, 4 ligaments and tendons of 4 muscles stabilize it

Glenohumeral joint muscles

Supraspinatus, infraspinatus, subscapularis, teres minor

Tibiofemoral Joint

Knee joint, hinge, mono-axial, has menisci, 2 intracap ligaments 5 extracap ligaments

Tibial collateral ligament

Fibular collateral ligament

Patellar ligament

Oblique popliteal ligament

Arcuate popliteal ligament

Anterior cruciate ligament (intracapsular)

posterior cruciate ligament (intracapsular)

4 Types of Bone Cells

Osteogenic, osteoblasts, osteoclasts, osteocytes

Osteogenic Cells

Bone stem cells, turn into osteoblasts, formed from mesenchyme

Mesenchyme

embryonic connective tissue

Osteoblasts

Build bones, synthesize organic compounds of bone matrix, initiate calcification, eventually turn into osteocytes

Osteocytes

Mature bone cells, maintain bone tissue, sense bone microdamage and stress, send signals for repair

Osteoclasts

Break down bone (bone resorption) by releasing enzymes and acids to degrade the collagen and release the minerals into blood, derived from myeloid stem cells

Step 1 of Bone Repair/Remodeling (Activation)

preosteoclasts are stimulated and turn into mature osteoclasts

Step 2 of Bone Repair/Remodeling (Resorption)

Osteoclasts digest mineral matrix

Step 3 of Bone Repair/Remodeling (Reversal)

Resorption ends, osteoblasts are recruited to scene

Step 4 of Bone Repair/Remodeling (Formation)

Osteoblasts synthesize new bone matrix

Step 5 of Bone Repair/Remodeling (Quiescence)

Osteoblasts become resting bone lining cells on newly formed bone

Organic Components of Bone

Ground substance (GAG), collagen fibers

Inorganic Components of Bone

Water, hydroxyapatite

Rickets

Inorganic component deficiency, calcium deficiency due to lack of vitamin D, overly flexible bones

Scurvy

Organic component deficiency, problem with collagen synthesis due to vitamin C deficiency, brittle bones

Spongy Bone

Irregular lattice of trabeculae, surrounds marrow cavities, in epiphyses, in flat short or irregular bones, withstands force, lightens skeleton, contains red marrow for hemopoiesis

Compact Bone

Solid network of osteons, found in external layer of all bones and diaphysis of long bones, withstands forces along longitudinal axis

Diaphysis

shaft of long bones

Soft Bones in Infants

Fontanels, Epiphyses of long bones, epiphyseal plates

Ossification

The replacement of connective tissue with bone, either intramembranous or endochondral

Intramembranous Ossification

Occurs within membranes, turns mesenchyme into bone, makes cranial bones, facial bones, sternum

Step 1 of Intramembranous Ossification (Development of ossification center)

Mesenchymal cells become osteogenic cells , then osteoblasts, which then secrete bone matrix

Step 2 of Intramembranous Ossification (Calcification)

Osteoblasts deposit calcium into matrix, osteoblasts turn into osteocytes

Step 3 of Intramembranous Ossification (Formation of trabeculae)

ECM develops into trabeculae that fuse to form spongy bone

Step 4 of Intramembranous Ossification (Development of Periosteum)

Mesenchyme at periphery of bone develops into periosteum, spongy bone remodeled into compact bone

Heterotrophic Bone Formation

type of intramembranous ossification that creates sesamoid bones and bone spurs

Endochondral Ossification

Helps long bones grow in length at epiphyseal plate and forms most bones in body, has two types: primary and secondary

Step 1 Endochondral Ossification (Development of Cartilage Model)

Mesenchymal cells turn into chondroblasts which form cartilage model

Step 2 Endochondral Ossification (Growth of Cartilage Model)

Chondrocytes divide and grow the cartilage model, calcification begins

Step 3 Endochondral Ossification (Development of Primary Ossification Center)

Bone tissue replaces most cartilage, blood vessels penetrate and stimulate osteogenic cells to turn into osteoblasts, which then form the bone of the outer surface of the model and create the primary ossification center in the diaphysis

Step 4 Endochondral Ossification (Development of Medullary Cavity)

Osteoclasts invade newly formed bone and form marrow cavity, spongy bone gets turned into compact bone

Step 5 Endochondral Ossification (Development of Secondary Ossification Center)

Secondary ossification centers develop in epiphysis around the time of birth, and blood vessels begin to penetrate epiphysis

Step 6 Endochondral Ossification (Formation of Articular Cartilage and Epiphyseal Plate)

Spongy bone replaces most cartilage at epiphysis, articular cartilage and epiphyseal plate form

Primary Endochondral Ossification

Marrow cavity formed, replaces all cartilage within bone, located in diaphysis, occurs before birth

Secondary Endochondral Ossification

No marrow cavity formation, some cartilage is left in epiphyseal plates for growth and articular cartilage, located in epiphyses, starts around birth

Growth at Epiphyseal Plate

Either endochondral ossification or interstitial growth, the primary occurring on the diaphyseal side and the latter on the epiphyseal side of the plate

Step 1 of Growth at Epiphyseal Plate

Diaphyseal osteoclasts break down calcified cartilage

Step 2 of Growth at Epiphyseal Plate

Osteoblasts lay down spongy bone

Step 3 of Growth at Epiphyseal Plate

Chondrocytes continue to form collagen matrix at proliferating cartilage region

Step 4 of Growth at Epiphyseal Plate

Growth in length stops when osteoclasts and osteoblasts work faster than chondrocytes in the proliferating zone, so the epiphyseal plate closes and becomes epiphyseal line

Step 1 of Interstitial Growth

Mesenchymal cells differentiate into chondroblasts

Step 2 of Interstitial Growth

Chondroblasts build matrix and and become chondrocytes

Step 3 of Interstitial Growth

Chondrocytes divide and spread apart

Step 4 of Interstitial Growth

Cartilage tissues grow from within

Appositional Growth

widening of a bone, increases medullary cavity size, cortical width, and bone diameter

Step 1 of Appositional Growth

Ridges in periosteum create groove for periosteal blood vessel

Step 2 of Appositional Growth

Periosteal ridges fuse, forming an endosteum lined tunnel

Step 3 of Appositional Growth

Osteoblasts in endosteum build new concentric lamellae inward towards the center of the tunnel, forming a new osteon

Step 4 of Appositional Growth

Bone grows outwards as osteoblasts in the periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels

Fracture

break in continuity of a bone, two MAIN classifications are traumatic and pathologic

Traumatic Fracture

normal bone experiences abnormal force

Pathologic Fracture

abnormal bone experiences normal force

Greenstick fracture

Incomplete fracture that breaks like a baby twig

Subclassifications of Fractures

Non-displaced, displaced, open, closed, complete, incomplete

Non-displaced Fracture

complete fracture that does not result in separation of broken pieces

Displaced Fracture

complete fracture that does result in separation of broken pieces

Open (Compound) Fracture

Bone pieces break skin

Closed (simple) Fracture

bone doesnt pierce the skin

Transverse Fracture

Break along transverse axis

Oblique Fracture

break along oblique axis

Spiral fracture

break where pieces of bone rotate in position

Comminuted fracture

break where multiple small shattered pieces of bone exist

Avulsion fracture

Aka jersey finger, often happens in distal phalanx of the finger, soft tissue yanks the bone loose

Impacted fracture

two ends of a bone are crushed together to break it

Epiphyseal Fracture

break along epiphyseal plate/line

Incomplete vs Complete Fracture

Incomplete the bone is only cracked, complete bone is severed

Step 1 of Fracture Repair (Formation of Fracture Hematoma)

takes 6-8 hours, nearby bone cells die leading to swelling and inflammation, phagocytes and osteoclasts removed damaged tissue taking about 3-4 weeks

Step 2 of Fracture Repair (Formation of Fibrocartilage Callus)

takes 3 weeks, blood vessels grow into the hematoma, mesenchymal cells in periosteum turn into fibroblasts, chondroblasts, and osteogenic cells

Step 3 of Fracture Repair (Formation of Bony Callus)

3-4 months, formed via endochondral ossification, osteogenic cells turn into osteoblasts which then produce spongy bone

Step 4 of Fracture Repair (Bone Remodeling)

takes 6-9 months

Closed Reduction

bone pieces are put back into place without surgery

Open Reduction

surgical use of rods, pins, plates, etc. to position bone pieces in correct place for healing

3 Big Influences on Bones

Dietary (vitamins and minerals), hormones involved in calcium homeostasis, and exercise