Breakfast at seven...

Skeletal System: Functions, Structure, and Key Concepts

  • Functions of the skeletal system

    • Support and structure for the body
    • Movement (works with muscles to move joints)
    • Protection of vital organs (e.g., brain, spinal cord, thoracic organs)
    • Mineral storage (calcium, other minerals) – bones can release or store minerals as needed
    • Red blood cell production (bone marrow in long bones)
    • Note: The lecture mentions positive feedback loops in relation to homeostasis and reproduction/death, but for skeletal homeostasis the focus is on negative feedback loops to maintain balance; no-grading contexts may require follow-up for exact phrasing.

  • Homeostasis and feedback loops

    • Negative feedback loop keeps most body systems in balance
    • Positive feedback loops (mentioned in lecture) include processes like reproduction and certain growth patterns; these are separate topics and not the primary mechanism for skeletal homeostasis in routine conditions.

  • Planes and directional terms (review emphasized)

    • Sagittal plane: divides body into left and right; flexion/extension primarily occur here
    • Frontal (coronal) plane: divides body into anterior and posterior; abduction/adduction occur here
    • Transverse (horizontal) plane: divides body into superior and inferior; rotation occurs here
    • Terms of orientation: anterior (ventral), posterior (dorsal), superior (cranial), inferior (caudal), medial, lateral, proximal, distal

  • Basic bone terminology and tissue types

    • Bone tissue types
    • Compact bone: dense outer layer; forms the structural unit of cortical bone
    • Spongy (trabecular) bone: porous inner network; lighter and often found at the ends of long bones
    • Medullary (marrow) cavity: hollow center in long bones
    • Bone cells and matrix
    • Osteocytes: mature bone cells housed in lacunae; maintain bone tissue
    • Osteoblasts (bone-forming): build bone; derived from osteogenic cells
    • Osteoclasts (bone-resorbing): break down bone; release minerals (e.g., calcium)
    • Osteogenic cells: precursor cells that differentiate into osteoblasts
    • Osteons: functional structural units of compact bone
    • Trabeculae: lattice-like rods in spongy bone; contributes to strength with lightness
    • Lacunae: small chambers in bone that house osteocytes
    • Bone matrix: organic and inorganic components that give bone its strength

  • Cartilage in bones

    • Hyaline cartilage (articular cartilage): smooth surface at ends of bones in joints; reduces friction and cushions movement
    • Fibrocartilage: tougher cartilage in some joints/discs (e.g., intervertebral discs, menisci)
    • Calcified/elastic cartilage examples discussed in the lecture (e.g., ears have flexible cartilage)

  • Cartilage and epiphyseal growth

    • Epiphyseal plate (growth plate): line of growth in children; this plate elongates bone during development and forms the epiphyseal line after maturity; in lecture referred to as a growth line (note: some terms in the transcript are nonstandard or misspelled)

  • Bone classifications (major types)

    • Long bones (e.g., femur, humerus)
    • Short bones (e.g., carpals, tarsals)
    • Irregular bones (e.g., vertebrae, some facial bones)
    • Flat bones (e.g., skull bones, sternum)

  • Specific bone features and regions to know

    • Long bone anatomy terms
    • Shaft (diaphysis), ends (epiphyses), metaphysis, and medullary cavity
    • Epiphysis contains spongy bone with red marrow
    • Shaft terminology and growth plate proximity (epiphyseal region)
    • Features on surfaces
    • Condyle: rounded projection for articulation
    • Head: rounded end of a bone (often a proximal end)
    • Process: any projection that sticks out
    • Fossa, sulcus: depressions and grooves for muscle/tendon attachment or passageways
    • Foramen, meatus, canal, sinus: holes/passages in bones
    • Notable bone identifiers mentioned in the lecture
    • External auditory meatus: ear canal opening in the skull
    • Foramen magnum: large opening in the base of the skull where the spinal cord passes
    • Obturator foramen: large opening in the pelvis bone (ischium/pubis region)
    • Lacunae and osteocytes in compact bone
    • Skeleton arrangement terms
    • Trabeculae: the lattice-like network in spongy bone
    • Osteons: the circular structural units of compact bone; each osteon contains concentric lamellae and a central canal

  • Axial vs. appendicular skeleton

    • Axial skeleton: skull, vertebral column, ribs, sternum, sacrum, coccyx
    • Appendicular skeleton: everything else that attaches to the axial skeleton (limbs and girdles)
    • Pelvis: os coxae with three bones that fuse (ilium, ischium, pubis); acetabulum is the socket for the femoral head
    • Important note from lecture: pelvis (os coxae) is part of the appendicular skeleton; axial components are central (skull, spine, ribs, sternum, sacrum, coccyx)

  • The skull: bones and landmarks

    • Total bones in skull: 22 (cranial + facial bones)
    • Parietal bones: left and right; sutures connect cranial bones
    • Frontal bone, occipital bone, temporal bone (mentioned for reference to brain lobes associated with the skull)
    • Sutures: joints between skull bones
    • Facial bones mentioned: maxilla (upper jaw), palatine (hard palate)
    • Zygomatic and other facial bones were not exhaustively listed in the transcript

  • The vertebral column and its curvatures

    • Curvatures to know (from the lecture):
    • Cervical and lumbar regions: lordosis (anteriorly curved;