The Skeletal System Bones, joints, and connective tissues.

The Skeletal System

Bones, joints, and connective tissues

Skeletal System Functions

Support Protection of organs Framework for movement Mineral storage (calcium & phosphate) Hematopoiesis (Blood cell production in bone marrow)

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are needed to see this picture.

Axial vs. Appendicular Skeleton

Axial: Skull, rib cage, vertebraeAppendicular:Limbs and girdles (shoulder,pelvic)



Skeletal cartilage

Properties of cartilage: Made of mostly water Contains cells called chondrocytes Avascular and has no nerve endings (heals

very slowly) Stops growing during adolescence

(deteriorates from this point on) 3 different types



Types of Cartilage (see figure 6.1)

Fibrocartilage - resists very high compression forces (in knee and between vertebrae)

Hyaline - Most common1) articular - at joints2) costal - (connect ribs to sternum)3) respiratory - larynx and trachea4) nasal

Elastic - least common type - very flexible (external ear and epiglottis)

Types of Bones (see figure 6.2 pg.178)

Structure of a Long Bone Epiphyses - end of long

bone Diaphysis - shaft Articular cartilage - covers

epiphyses (provides cushion and lubrication at joints)

Periosteum - double membrane surrounding bone

Endosteum - lines inner cavities of bone



Structure of a Long Bone



•Medullary cavity - contains bone marrow

•Spongy (trabecular) bone - contains red marrow (found in epiphyses)

•Compact (cortical) bone - found in diaphysis

•Epiphyseal plate - hyaline cartilage from which bone growth occurs in childhood and adolescence

Microscopic Anatomy of Compact Bone (see Figure 6.6 on pg.183)




are needed to see this picture.Haversian Canal

Chemical Composition of Bone

Organic component (35%): bone cells and osteoid

Osteoid - secreted by osteoblasts (most collagen as well as other protein compounds)

Responsible for bone flexibilityInorganic component (65%): mineral

component Hydroxyapatites - Ca3(PO4)2 aka calcium

phosphate

Responsible for hardness of bone

Cell Types Osteoblasts - bone

building cells Osteoclasts -

resorb (break down) bone (secrete HCl)

Osteocytes - mature bone cells (maintain bone matrix)



What is Ossification?

Ossification (also osteogenesis) means “bone formation”

Starts before birth and extends throughout life

Types:- intramembranous ossification (forms bones of the skull as well as clavicles)- endochondral ossification (forms all bones below the skull and clavicles)

Endochondral Ossification Replacement of hyaline cartilage with bone -

see Figure 6.8 on pg 185 Ossification begins in the middle of the bone

(primary ossification center) At birth, epiphyses remain mostly

cartilaginous By early childhood, hyaline cartilage only

remains in the epiphyseal plate and covering the epipyses (articular cartilage)



Post-natal Bone Growth

Growth occurs from the epiphyseal plate (see left side of Figure 6.10 on pg.187)

Diaphysis also increases in width as bone lengthens (gives bone more stability)

Regulated by growth hormone (hGH) in childhood

Growth spurt in teen years cause by androgens (sex hormones):testosterone (males)estrogen (females)



Bone growth at epipyseal plate

Post-natal Bone Growth

After epiphyseal plate has completely ossified, bones can only grow in width (appositional growth)

Bone remodeling occurs throughout life

Bone deposit (osteoblasts) and bone resorption (osteoclasts) balance each other out in healthy young adults

See right side of Figure 6.10 on pg 187



Bone growth at epipyseal plate

Bone Remodeling Bone deposit and

bone resorption of the adult skeleton

Occurs to prevent bones from becoming brittle

Spongy bone is replaced every 3-4 years; compact every 10 years

Control of Bone Remodeling Mechanical stress

weight bearing activity leads to bone deposit to strengthen areas most in need (Wolff’s Law)

Hormonal control (see figure 6.12 on pg. 189) Calcitonin - stimulates bone deposit Parathyroid hormone (PTH) - stimulates bone resorption

Types of fractures (pg.191)Nondisplaced vs. displacedComplete vs. incompleteLinear vs. transverseOpen (compound) vs. closed (simple)

* Fractures are treated with closed reduction (hands are used to align bone ends) or open reduction (screws, rods, wires, etc are used to keep bone ends together)

What is a joint? Area where two

bones meet

Ligaments and Tendons

Ligaments Connect two bones

together at a joint

Tendons Connect muscles to

bones

Joint Classification (structural) fibrous - bone ends joined

by fibrous tissue (ex. Sutures in skull, teeth in sockets)

cartilaginous - bone ends joined by cartilage (ex. Vertebral joints, pubic symphysis)

synovial - bone ends covered by cartilage and surrounded by a fluid filled joint capsule lined with a membrane (all joints of the limbs and most joints in the body)

Joint Classification (functional) Synarthroses -

immovable joints (ex. Sutures in skull)

Amphiarthroses - slightly movable (ex. Vertebral joints)

Diarthroses - movable (most joints)

Joint Classification (functional) Synarthroses -

immovable joints (ex. Sutures in skull)

Amphiarthroses - slightly movable (ex. Vertebral joints)

Diarthroses - movable (most joints)







Synovial joint movements and types of synovial joints

Movements allowed by synovial jointsSee pages 260-263

Types of Synovial jointsPlane, pivot, hinge, condyloid, saddle,

ball-and-socketSee pages 264-265

Synovial Joints - a type of diarthrotic joint

Bursae and Tendon Sheaths Function to reduce

friction during joint movement

Bursae are fluid filled sacs found where ligaments, muscles, tendons, skin, and bones rub together.

Tendon sheaths wrap around tendons that are subjected to friction





Synovial joint movements and types of synovial joints

Movements allowed by synovial jointsSee pages 260-263

Types of Synovial jointsPlane, pivot, hinge, condyloid, saddle,

ball-and-socketSee pages 264-265

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The Skeletal System Bones, joints, and connective tissues.

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