Vertebrates 6 - Skeletal system Flashcards
Cartilage
Rigid, flexibility, tensile strength.
Structure of cartilage
Living chondrocytes secrete ECM (high in collagens and glycoproteins). Chondrocytes are in lacunae. Chondroblasts are precursors
Hyaline cartilage
in ends of bones/ribs, larynx, trachea. Pretty rigid
Elastic cartilage
Less rigid. Has more elastin. Pinna of ear, epiglottis.
Fibrocartilage
Pretty rigid. Intervertebral disks (shock absorber)
Cellular cartilage
Agnathan internal skeleton. Less matrix, more cells.
Calcified cartilage
Internal skeleton of Chondrichthyes. Rigid, almost as rigid as bone.
Bone
More vascular; mineralized, dense, hard.
Cells in bones
Osteoblasts: precursors; Osteocytes: secretory; osteoclasts: bone reuptake
Bone structure
Osteocytes secrete matrix and collagen, organized. Mineral deposit there, esp. Ca2PO4.
Membrane/Dermal Bone
Skull. Near body surface/beneath dermis
Endochondral
Long bones; form from cartilage; spongy and/or compact; have bone marrow
Functions of bone
support and shape of body. Locomotion. Ion reservoir. Marrow (RBC)
Fibrous joints
aka sutures. Immovable. example: in skulls.
Cartilaginous joints
aka symphyses. Some flexibilty. Eg. in b/w pubic bones (becomes more loose with prostaglandins at birth), mandibular (two halves - no flexibility in humans)
Snake jaws
No mandibular symphysis, rather an elastic ligament. Helps swallow large prey. Also have double joint at quadrate bone.
Synovial joints
Mobility. Knees, etc. Contain synovial membranes b/w joints to seal it and secrete synovial fluid. Cartilage (hyalin) protects ends of bone.
Synovial fluid
Contains glycoproteins, lipids. Acts as lubricant in a synovial joint
Reading: Cortical and cancellous bone
aka compact and spongy bone, respectively. Both are important in strength of bone.
Reading: Birds bones vs mammal bones
Less compact bone to spongy bone. Less weight, but a bit less strong.
Reading: Bone turnover
Rate of bone reuptake and formation. Constantly in flux
Reading: what is osteoporosis? What are risk factors?
Decrease in bone density. Postmenopausal women or post ovariectomy, women have generally lower density (less weight and muscle), lifestyle, nutrition
Reading: Four experiments with rat osteoporosis
- OVX or sham - measure bone loss. 2. OVX, then 2 weeks in space or earth. 3. OVX or sham, treadmill. 4. OVX or sham, cut sciatic nerve + estrogen replacement.
Reading: What part of femur had most bone loss?
Metaphysis spongy bone, middle is nearly hollow. Epiphysis had little change.
Reading: What happened to the rats on the space shuttle?
Decrease in metaphysis and epiphysis because no strain from gravity.
Reading: OVX and treadmill rats
More stress prevented loss of bone compared to non-exercise
Reading: what happened to the rats with sciatic nerve cut?
Loss bone in epiphysis and more in metaphysis. Less loss if leg was stressed (can’t move on own), and less loss with estrogen replacement.
Reading: how does estrogen work?
Estrogen stimulates apoptosis in osteoclasts so less reuptake, and stimulates a bit of bone formation.
Reading: what conclusions does this study of osteoporosis have?
Exercise is important to maintain bone density; nutrition is important; some drugs (bisphosphonates) slow osteoclasts
