Skeletal System Flashcards
Identify the functions of the skeletal system.
Support – framework that supports body and cradles organs, like rib cage supporting thoracic wall
Protection – fused bones of skull protects brain
Movement – skeletal muscles attach to bones by tendons and use bones as levers to move the body and parts
Storage of minerals and growth factors – reservoir for minerals, most importantly calcium and phosphate
Hemopoiesis (blood cell production) – red marrow cavities of certain bones
What are the four basic components of the skeletal system?
Bones
Cartilages
Ligaments
Articulations
Describe the general characteristics of cartilage, paying attention to the location of perichondrium, blood vessels & nerves, and chondrocytes as well as to the general composition of the extracellular matrix.
Contains no nerves or blood vessels, is surrounded by a layer of dense irregular connective tissue
Perichondrium acts like a girdle to resist outward expansion when the cartilage is compressed, contains blood vessels from which nutrients diffuse through the matrix to reach cartilage cells internally
Flexible matrix that can accommodate mitosis
Ideal tissue to use to rapidly lay down embryonic skeleton and provide for new skeletal growth
Mesoderm → mesenchyme → embryonic skeleton (composed of cartilage and fibrous membranes)
Compare and contrast the three types of skeletal cartilage. Thinking about where each type of cartilage is located in the body, describe how the structure of each type supports its function.
Hyaline cartilage - provides support with flexibility and resilience, most abundant in ends of bones at movable joints and costal cartilage, spherical chondrocytes, fiber type collagen
Elastic cartilage - contains more stretchy elastic fibers and able to stand up to repeated bending, found in external ear and epiglottis(flap covering larynx when we swallow)
Fibrocartilage - highly compressible with great tensile strength, roughly parallel rows of chondrocytes alternating with thick collagen fibers, found in sites subjected to pressure and stretch like menisci and discs between vertebrae
Identify and describe the two mechanisms of cartilage growth.
Appositional growth - cartilage forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue
Interstitial growth - lacunae bound chondrocytes divide and secrete new matrix, expanding cartilage from within and typically ends during adolescence
What bones make up the axial skeleton? How many bones are included in the axial skeleton?
Axial skeleton – long axis of body and they protect, support, carry other body parts; skull, vertebral column and rib cage
What bones make up the appendicular skeleton? How many bones are included in the appendicular skeleton?
Appendicular skeleton – bones of upper and lower limbs and girdles that attach limbs to axial skeleton
Name, describe, and give an example of each of the four categories of bone, classified by shape.
Long bones – longer than they are wide, shaft plus two ends, all limb bones except patella, wrist and ankle bones are long bones
Short bones – cube shaped, like bones of wrists and ankles.
Flat bones – thin, flattened, a bit curved like sternum, scapulae, ribs and most skull bones
Irregular bones – vertebrae and hip bones are examples that fit none of preceding classes
What is resorption?
breaking down of bone
What is an osteogenic cell?
Osteogenic cell – osteoprogenitor cells, mitotically active stem cells found in membranous periosteum and endosteum. Differentiate into osteoblasts or bone lining cells. Are flattened or squamous cells in growing bones.
Four types of cells that form and maintain bone tissue?
osteogenic cells, osteoblasts, osteocytes, osteoclasts
What is an osteoblast?
Osteoblasts – bone-forming cells that secrete bone matrix and close relatives of fibroblasts and chondroblasts. All are actively mitotic. They secrete bone matrix that includes collagen and calcium-binding proteins that make up initial unmineralized bone (osteoid) and play a role in matrix calcification
What is an osteocyte?
Osteocytes – spidery, mature bone cells that occupy spaces (lacunae) that conform to their shape. Osteocytes monitor and maintain bone matrix. If they die, surround matrix is resorbed. Stress or strain “sensors” and respond to mechanical stimuli and communicate this to cells responsible for bone remodeling (osteoblasts and osteoclasts) so that bone matrix can be made of degraded as necessary to preserve calcium homeostasis.
What is an osteoclast?
Osteoclasts – giant multinucleate cells located at sites of bone resorption derived from same hematopoietic stem cells that differentiate into macrophages. When actively resorbing bone, osteoclasts rest in resorption bay (ruffled border) that directly contacts the bone. Plasma membrane infoldings of that ruffled border tremendously increase surface area for enzymatically degrading the bones and seal off that area from surrounding matrix.
