EQ: What are the basic Bones of the Body?

The Basic Structure and Function of the Skeletal System:

• Bone Tissues:

  • Bones are actively modeling and remodeling organs.

  • Bones are made of cells within a hard extracellular matrix.

  • Lots of solid extracellular matrix containing

    • Inorganic salts (calcium and phosphorus) for hardness

    • Collagenous fibers for reinforcement and flexibility

  • Cells are dispersed in the matrix to maintain homeostasis of the tissue

    • Osteoclast: Breakdown/absorb bone tissue for remodeling

      • Found on bone surfaces

    • Osteoblast: Secrete the matrix of bone tissue

      • Found on bone surfaces

      • Become osteocytes when enclosed by matrix

    • Osteocytes: Principle bone cells

      • Maintain condition of bone

      • Found within spaces (lacunae) within the bone

      • Small tunnels (canaliculi) connect them to each other and to blood vessels

• Functions of the Skeletal System:

  • Framework and Support: Adds shape and structure to the body.

  • Body Movement: Skeletal muscles attach and the bones work as levers.

  • Protections: (example) skull protects brain, and rib cage protects heart and lungs.

  • Formation of Blood Cells (hematopoiesis): Red marrow within spongy bone produces blood cells.

  • Mineral Salt Storage: Bones absorb and release inorganic salts as needed by the body.

Skeletal Organization:

• Bones are found within the axial or appendicular skeleton.

  • AXIAL Skeleton - Skull, hyoid, vertebral column, rib cage.

  • APPENDICULAR Skeleton - Shoulder girdle, upper appendages, pelvic girdle, lower appendages.

Terms used to describe skeletal structures:

• Fovea - pit or depression

• Fossa - pit or depression

• Foramen - hole

• Meatus - tube like passageway

• Sinus - cavity within a bone

• Suture - interlocking between bones

• Process - projection

• Head - projection

• Condyle - projection

• Epicondyle - projection

• Trochanter - projection

• Tubercle - projection

• Tuberosity - projection

• Crest - projection

• Spine - projection

Bone Structure:

• Classification:

  • Long Bones - long axis with expanded ends (arms, legs, hands/fingers)

  • Short Bones - cube-like (carpals/tarsals)

  • Flat Bones - plate-like (ribs, cranium, sternum)

  • Irregular Bones - variety of shapes (vertebrae, facial bones)

  • Sesamoid (round) Bones - round and embedded in tendons adjacent to joints (kneecap)

• Macroscopic Anatomy of the Longbone -

  • Spongy (trabecular) bone:

    • Location - Interior of bones

    • Structure - Branching structures called trabecular

    • Function - Reduce weight of bone

  • Compact (cortical) bone:

    • Location - Exterior of bones

    • Structure - Tightly packed

    • Function - Strength

  • Diaphysis: long, hollow, central shaft, largely compact.

    • Medullary Cavity: Hollow chamber of diaphysis.

      • Contains yellow bone marrow (adipose tissue)

  • Epiphysis: Widened ends of bone, largely spongy tissue.

    • Contains red marrow: produces blood cells

  • Periosteum: Dense, connective tissue membrane enclosing bone.

    • Contains osteoblast and osteoclast for growth, development, and repair.

  • Articular Cartilage: Cartilage over each epiphysis

    • Smooth motion at the joint

• Microscopic Anatomy of the Compact Bone -

  • Background:

    • When formed, all bones is spongy.

    • Outer surface must be converted to compact.

  • The Process of Building Compact Bone:

    • In porous area of spongy bone. osteoblast lay down concentric layers of matrix (lamellae) - one inside the other.

    • This forms a ring structure called an osteon or haversian system around very small canal (central or haversian canal) for blood vessels

    • Osteoblast get trapped in spaces called lacunae.

      • Become Osteocytes and they have branches of Canaliculi.

• Bone Formation and Homeostasis -

  • Skeletal System Development:

    • In the fetus, the skeleton begins as either membranes of connective tissue or cartilage.

    • These tissues are replaced by bone tissue during the prenatal development (pregnancy).

    • Growth (epiphyseal) plates are just regions that have not fully “ossified”.

  • Homeostasis of Bone Tissue:

    • Once the bones have formed, they are constantly modeled and remodeled.

    • Osteocytes constantly maintain the condition of the bone from within.

    • Osteoclast and osteoblast constantly “ remodel” the bone by resorbing old or damaged tissue and replacing it with new tissue.

    • In adults, about 10% of the skeleton is remodeled annually.

    • If extra stress is added to the bones (heavy exercise), osteoblast will outwork osteoclast.

    • If bone experiences less stress than normal, osteoclast will outwork osteoblast.

  • Healing Bone Fractures:

    • In adults, about 10% of the skeleton is remodeled annually.

    • If bones experiences less stress than normal, osteoclast will outwork osteoblast.

    • Blood escapes from ruptured blood vessels and spreads throughout the damaged area and forms a blood clot (hematoma).

    • Inflammation begins, blood vessels, phagocytes, fibroblast and osteoblast invade clot.

    • Fibroblast create “soft callus” of fibrocartilage to bond the broken edges. Osteoblast from spongy bone within. Phagocytes remove the clot.

    • Osteoblast replace the cartilage with bone to form a bony callus.

    • Osteoclast and osteoblast remodel the bony callus to be very similar to the original bone.

Arthrology: The study of joints and their motions.

• Three Classes of Joints -

  • Fibrous Joints: Generally immovable.

    • Bones connected by dense connective tissue.

    • Ie. Suture in skull and distal tibiofibular joint.

  • Cartilaginous: Slight movement.

    • Bones connected by hyaline or fibrocartilage.

    • Ie. Intervertebral discs between 2 vertebrae.

  • Synovial: Freely movable.

    • Bones ends are covered with articular cartilage and surrounded by a dense connective tissue capsule.

    • Inner capsule is lined by synovial membrane.

      • Secretes synovial fluid to lubricate the joint.

    • May also contain menisci (fibrocartilage pads) or bursae (fluid filled synovial sacs that help tendons guide smoothly over bones)

• Six Types of Synovial Joints:

  • Ball and Socket: A ball is cupped by another bone.

    • Movement in three planes (sagittal, frontal, and transverse)

    • Ie. only hip and shoulder joints

  • Condylar (ellipsoidal): Oval condyle in an elliptical cavity (convex in a concave)

    • Movement in two planes (sagittal and frontal)

    • Ie. Radius and carpals at wrist and metacarpals on phalanges

  • Gliding (Plane): Flat surfaces sliding over each other.

    • Some sliding and twisting in a planes

    • Ie. carpal on carpal

  • Hinge: Acts like a door hinge.

    • Movements in one plane (Sagittal)

    • Ie. Joints between phalanges and between the ulna and humerus.

  • Pivot: One bone rotates in a cusp of another.

    • Rotation motion in one plane (transverse)

    • Ie. Radius and ulna joint and atlas on axis at base of skull.

  • Saddle: Like legs straddling a saddle.

    • Motion in two planes (sagittal and frontal)

    • Ie. Only the thumb carpal on metacarpal

• Joint Articulations:

  • Flexion - Bending or decreasing the angle between parts. (Saggital Plane)

  • Extension - Stretching out, opposite of flexion. (Saggital Plane

  • Rotation - Turning on axis. (Medial and Lateral + Transverse Plane)

  • Abduction - Drawing away from the body’s midline. (Frontal Plane)

  • Adduction - Moving toward the body’s midline, opposite of abduction. (Frontal Plane)

  • Hyperextension - Extension beyond the anatomical position. (Saggital Plane)

  • Dorsiflexion - Flexion of the ankle resulting in the toes moving upward. (Saggital Plane)

  • Plantar Flexion - Bending at the ankle resulting in the toes moving downward (pointing). - Saggital

  • Circumduction - Moving a part so that its end follows a circular path. Frontal + Saggital

  • Eversion - Turning the plantar surface of the foot outward so that its lateral border is elevated. (Frontal)

  • Inversion - Turning the plantar surface of the foot inward so that its medial border is elevated. (Frontal)

  • Pronation - Rotation of the forearm resulting in the palm moving posteriorly/down. (Removing Soup)

  • Supination - Rotation of the forearm resulting in the palm moving anteriorly/up. (Collecting Soup)

  • Protraction - Moving a part forward.

  • Retraction - Moving a part backward.