Anatomy Unit 2: Skeletal System and Muscle Tissue

Osteons

Repeating structural units in compact bone, consist of lamellae, central canal, lacunae, and canaliculi

Bone remodeling

Replacement of old bone with new bone, bone resorption by osteoclasts and bone deposition by osteoblasts

Periosteal arteries

Small arteries that enter the bone through the periosteum, supply periosteum and outer part of compact bone

Lacunae

Spaces between lamellae in compact bone, contain osteocytes

ECM of bone

15% water, 30% collagen, 55% crystallized mineral salts

Electrical excitability

Ability of muscle and nerve cells to respond to certain stimuli by producing action potentials

Contractility

Ability of muscle to contract forcefully when stimulated

Elasticity

Ability of muscle to return to its original length and shape

Extensibility

Ability of muscle to stretch without being damaged

Epiphyseal arteries

Arteries that enter the epiphysis, supply red marrow and tissue of epiphysis

Metaphyseal arteries

Arteries that enter the metaphysis, supply red marrow and tissue of metaphysis

Medullary cavity

Cavity within the diaphysis, contains yellow marrow and blood vessels

Canaliculi

Channels filled with extracellular fluid in compact bone, connect osteocytes with one another

Lamellae

Concentric circles of mineralized ECM in compact bone

Attachment for tendons

Connective tissue that connects skeletal muscles to bones

Endomysium

Connective tissue that penetrates the interior of each fascicle and separates individual muscle fibers

Periosteum

Connective tissue that surrounds bone, helps with fracture repair, nourishes bone tissue, and serves as attachment for ligaments and tendons

Perimysium

Connective tissue that surrounds groups of muscle fibers and separates them into bundles called fasicles

Yellow marrow

Consists of mainly adipose cells, stores triglycerides

Central canal

Contains blood vessels, nerves, and lymphatics in compact bone

Fascia

Dense sheet or band of connective tissue that surrounds and supports muscles and organs

Structure of long bones

Diaphysis, epiphysis, metaphysis, articular cartilage, periosteum, medullary cavity, endosteum

Spongy bone

Does not have osteons, consists of trabeculae, filled with red marrow

Assistance in movement

Enables movement of body parts

Hypercalcemia

Excess calcium in the blood, can be caused by over-active parathyroid or certain cancers

Stress fractures

Fractures caused by repetitive forces on the bone

Skeletal system

Framework for the body, support, protection, movement

Appositional growth

Growth in bone thickness, periosteal cells differentiate into osteoblasts and secrete collagen fibers to form ECM

Parathyroid hormone (PTH)

Hormone that increases calcium in the blood, stimulates osteoclasts and decreases calcium loss through urine

Calcitonin

Hormone that inhibits osteoclasts and speeds up calcium uptake by the bone

Osteoclasts

Huge cells derived from fusion of monocytes, release enzymes and acids that digest ECM, called resorption

Nutrient artery

Large artery that enters the diaphysis through the nutrient foramen, supplies inner part of compact bone, spongy bone tissue, and marrow

Diaphysis

Long, main portion of the bone

Hypocalcemia

Low calcium in the blood, can be caused by hypoparathyroidism or kidney disease

Mineral homeostasis

Maintains balance of calcium and phosphate in the body

Calcium homeostasis

Maintenance of calcium balance in the body, bone is major calcium reservoir

Osteocytes

Mature bone cells, maintain daily metabolism

Skeletal muscle

Muscle attached to bones, striated, voluntary

Smooth muscle

Muscle in walls of internal structures, non-striated, involuntary

Cardiac muscle

Muscle that forms the heart, striated, involuntary, has its own pacemaker

Nerve and blood supply

Muscles are well supplied with blood and nerves, somatic motor neurons stimulate contraction, proprioceptors provide information about force generated at tendons

Nerve supply

Nerves accompany blood vessels, provide sensory and motor innervation to the bone

Epimysium

Outermost layer of connective tissue that encircles the muscle

Nociceptors

Pain receptors

Hematopoiesis

Process of blood cell production

Calcification

Process of depositing mineral salts in bone tissue, initiated by osteoblasts

Red marrow

Produces red blood cells, white blood cells, and platelets

Protection

Protects internal organs

Epiphysis

Proximal and distal ends of the bone

Blood cell production

Red marrow in bones produces red blood cells, white blood cells, and platelets

Metaphysis

Region between the epiphysis and diaphysis, contains the epiphyseal line

Bone resorption

Removal of minerals and collagen fibers from bone by osteoclasts

Perforating fibers

Thick bundles of collagen that extend from periosteum to the bone

Trabeculae

Thin columns of lamellae in spongy bone, filled with red marrow

Articular cartilage

Thin layer of cartilage covering the epiphysis where bone forms joints

Endosteum

Thin membrane that lines the medullary cavity, contains bone forming cells and connective tissue

Muscle tissue

Tissue responsible for producing body movements, stabilizing body positions, generating heat, and storing/moving substances

Connective tissue

Tissue that surrounds and protects muscle tissue, includes fascia, epimysium, perimysium, and endomysium

Epiphyseal veins

Veins that accompany the epiphyseal arteries, exit through the epiphysis

Nutrient veins

Veins that accompany the nutrient artery, exit through the diaphysis

Periosteal veins

Veins that accompany the periosteal artery, exit through the periosteum

Osteogenic cells

Bone stem cells, undergo cell division and become osteoblasts

Osteoblasts

Bone-building cells, secrete collagen fibers and other components to make the ECM, initiate calcification

Store calcium and phosphate

Skeletal system stores calcium and phosphate for use in the body

Bone fracture

Break in a bone, can be closed, open, or greenstick

Bone deposition

Addition of minerals and collagen fibers to bone by osteoblasts

Proprioceptors

Sensory receptors that provide information about force generated at tendons

Compact bone

Strongest form of bone tissue, made up of osteons

Support

Structural framework for the body

Structural framework

Support for the body

Functions of the skeletal system

Support, protection, movement, mineral homeostasis, blood cell production, triglyceride storage