Anatomy Section 3

Skeletal System

System/ Organ System

a group of organs that work together as a biological system to perform one or more related tasks or functions

12 Major Organ Systems

Nervous, Immune, Skeletal, Cardiovascular, Respiratory, Digestive, Muscular, Lymphatic, Reproductive, Integumentary, Endocrine, & Excretory

2 Parts of the Skeletal System

Axial & Appendicular

Axial Skeleton

Composed of the vertebral column, rib cage, and skull; protects the tissues and organs

Appendicular Skeleton

Made up of the shoulder & pelvic girdles, & the limbs; purpose is movement

Functions of the Skeletal System

Movement, Protection, Blood Cell Production, Calcium and Iron Storage, Endocrine Regulation

Bone Remodeling

When you have tiny cracks in your bones from basic activities and your bones must be repaired so they do not actually break

Bone Density

how packed the bones are with cells; hits peak at 21 years old and after 35 bone density lessens

Osteoporosis

advanced state of bone density loss resulting in weak and brittle bones that break easily

3 Types of Skeletal Tissue

Osseous Tissue, Cartilage, Fibrous Connective Tissue

Osseous Tissue

The actual bone, constantly repairing itself, blood cells are produced here, and contains a large blood supply

Types of Bone Cells

Osteocyes, Osteoblasts, Osteoclasts, Osteogenic Cells

Osteocytes

bone cells that are formed when an osteoblast becomes embedded in the matrix that it has secreted

Osteoblasts

bone cells that secrete the matrix for bone formation

Osteoclasts

large, multinucleate bone cells which absorb bone tissue during both growth & healing

Osteogenic Cells

the only bone cells that divide, hey differentiate and develop into osteoblasts

Cartilage

flexible and smooth elastic tissue which serves as a rubberized padding protecting the ends of long bones at joints

Major component of: ribcage, ears, nose, etc.

Types of Cartilage

Mature Cartilage (Main) > Cartilaginous Tissues (sub-categories): Elastic Cartilage, Hyaline Cartilage, Fibrocartilage

Mature Cartilage

composed of cells called chondrocytes which are formed from chondroblasts

Elastic Cartilage

only type not found in association with the skeleton

Ex. external ear

Hyaline Cartilage

forms the septum of your nose and is the most common form of cartilage found in your joints

Ex. Freely moving joints: elbow or knee and fetal skeleton

Fibrocartilage

a less common dense fibrous tissue that acts more like a shock absorber than a smooth surface allowing movement

Ex. invertebral discs of the spinal column

Fibrous Connective Tissue

stuff that holds the rest of the skeletal structures together, no blood flow and not made up of living cells

Periosteum

protective lining that covers the bones and also makes up both tendons and ligaments

Ligaments

attach bone to bone

Tendons

attach bone to muscle

Bone Structures

Flat bones (protection), Short bones (wide range of motion), Irregular bones (attachments for tendons or ligaments)

Compact or Cortical Bone

outer portion of the bone, gives bone their hardness and strength, covered in the periosteum

Spongy or Trabecular Bone

middle layer of the bone, loosely packed structure, lighter but not as strong as compact bone

Trabeculae

act like support trusses & support stress regions of each bone

Yellow Marrow

very fat-rich and found in the medullary cavaties

Red Marrow

where blood cells are produced and found within the spongy bone

Epiphysis

large, rounded portions found at the end of many long bones where the growth plate can be found

Immovable Joints (synarthroses)

joints where bone connects to bone through an interlocking system we call a suture

Ex. Skull bones

Slight movement (Amphiarthroses) joints

connected by fibro- or hyaline cartilage

Ex. intervertebral discs

Freely Moving (Diarthroses) Joints

Also called synovial joints, have a capsule between 2 bones filled with synovial fluid which cushions impact and allows for easy movement, ends are covered with hyaline cartilage

Condyloid Joint

rounded shape (condyle) of one bone fits into the cavity of another bone, allows for great range of motion but no rotation

Ex. knuckles

Gliding Joint

flat joint or has a mildly curved surface between bones, allows for sliding motions on 2 different planes

Ex. wrist & ankles

Ball & Socket Joint

Spheroid shape of one bone inserts into the depression of another, allows for circular rotational movement

Ex. Hip & Shoulders

Saddle Joint

bone is saddle shaped and fit into the opposing bones saddle, allows for great range of motion but no rotation

Ex. joint of thumb

Pivot Joint

tubular portion of one bone fits within a ring of another bone, supported by ligaments and allows only for rotation

Ex. Atlas & Axis

Hinge Joint

Concave bone articulates with a convex bone, allows for back and forth motion on one plane only

Ex. Elbows and knees

Haversian Canal

Central point in compact bone tissue that creates a space for blood vessels & nerves that run through bone

Osteon

a set of concentric circles in compact bone tissue

Lamella

an individual concentric circle in the compact bone tissue which are formed as calcium is secreted into the bone matrix

Lacunae

small recesses that osteocytes are frozen in place to

Canaliculi

little tunnels through the bone tissue that emanate from the lacunae which allows the osteocyte to gain nutrients