Form and Function Exam 2

Osteology

The study of the skeletal system

Key components of the skeletal system

• Bones

• Cartilage

• Joint

• Ligaments

Tricalcium Phosphate (Ca3(PO4)2)

Strength and rigidity of bone

Ossein

Gelatin-like protein that gives bone flexibility and resiliency.

Medium for nourishment of tissue

Cartilage

• Composed of chondrocytes embedded in a mucoprotein matrix

• Gristly flexible tissue attached to, or associated with, joint surfaces.

Softer and more flexible than bone. Less capable of regeneration once damaged.

Bones

Living structures containing

• Blood vessels

• Lymphatic vessels

• Nerves

Subject to disease and can undergo repair throughout life.

Major functions of Bones

• Protect vital organs

• Muscles attach to bones

• Dynamic storage of minerals

• Blood formation

Compact Bone

Dense, solid-looking bone tissue that forms the strong outer wall of a bone.

It is organized into osteons and provides strength and resistance to bending.

Cancellous Bone

It consists of a porous network of trabeculae, making bone lighter while still resisting stress from multiple directions. Its spaces often contain red bone marrow.

• Also called spongy or trabecular bone

Medullary Bone

The hollow central cavity within the diaphysis of a long bone.

It contains bone marrow, primarily yellow marrow in healthy adult animals, and is lined by the endosteum.

Epiphysis

Either end of a long bone usually contains cancellous bone with a thin layer of compact bone

Diaphysis

Cylindrical shaft of a long bone- surrounds the medullary cavity

Metaphysis

• Flared area adjacent to the epiphysis

• Contains a growth plate in immature animals

Epiphyseal Cartilage

• Layer of hyaline cartilage between the epiphysis and diaphysis

• Allows bone to grow in length

• Becomes the epiphyseal line when skeletal growth is complete

Classification of Bones

• Long Bones

• Short Bones

• Flat Bones

• Sesamoid Bones

• Pneumatic Bones

• Irregular Bones

Long Bone

• Longer than they are wide

• Primary functions as levers for movement and support body weight

• Consists of a cylindrical diaphysis and two expanded epiphyses

Ex. Humerus, Tibia, Radius, Femur, and Ulna

Short Bones

• Equal in length, width, and thickness (cuboidal)

• Provide stability and support

• Allows limited movement while absorbing and distributing forces

• Composed of cancellous bone surrounded by a thin layer of compact bone

Ex. Carpal bones of the knee, Tarsal bones of the hock

Flat Bones

• Thin, Flattened, and often slightly curved

• Protects internal organs and provides broad areas for muscle attachment

• Two layers of compact bone surround an interior layer of cancellous bone

Ex. Ribs, Sternum, Scapula, and Bones of skull

Sesamoid Bones

• Small, rounded bones that develop WITHIN tendons

• Reduce friction and protect the tendon from compression; increase the muscle’s mechanical advantage (pulley)

• Located where a tendon crosses a joint

Ex. Patella, Navicular Bone

Pneumatic Bone

• Contains air-filled spaces rather than bone marrow

• Internal bony struts provide support without substantially increasing weight

• Pneumatic Foramen (Hole)

• Most extensively developed in birds

Irregular Bone

• Complex shapes that do not fit the other bone classifications

• Protects nervous tissue and internal structures, providing multiple surfaces for muscle and ligament attachment

• Composed of cancellous bone surrounded by a thin layer of compact bone

Hyaline Cartilage

• Most common

• Bluish-white substance found on joint surfaces of movable bones

Elastic & Fibrocartilage

Yellow elastic tissue or white fibrous tissue within cartilage, in addition to chondrocytes and matrix

Perichondrium

A thin membrane that covers all cartilage

Syndesmology

The study of articulations/joints between bones

Simple Joint

Two articulating bones

Complex Joint

Two or more articulating bones

Fibrous Joints

• Connected by dense connective tissue

• No joint space

• Little or no movement

Suture Joints -Connects bones of the skull

Cartilaginous Joints

• Bones connected by cartilage

• Permits limited movement

Synchondrosis joint- growth plate

Synovial Joint

• United by a joint capsule

• Freely movable

• Reinforced by ligaments

Bones are separated by a fluid-filled joint cavity

Joint Capsule

Encloses and stabilizes the joint (outer fibrous layer with inner synovial membrane)

Ligaments

Connects bone to bone limits excessive movement

Embryonic Development

Starts with hyaline cartilage blueprint

Ossification

Begins in areas of mesenchymal cell condensation/recruitment

Intramembranous Ossification

• Bone develops directly from mesenchymal/connective tissue

• No cartilage model

• Primarily forms flat bones, many bones of skull

Endochondral Ossification

• Bone develops by replacing a pre-existing hyaline cartilage model

• Forms most bones of the skeleton, esp. long bones

Periosteal Bud

• Vascular tissue that invades bone after chondrocytes die

• Carries Osteoprogenitor cells, Hematopoietic cells, Osteoclast/chondroclast precursors

Periosteal collar

• Perichondrium surrounding cartilage becomes vascularized

• Osteoprogenitor cells migrate to tissue

• Osteoblasts secrete osteoid

Creates the periosteum:

• Leads to the death of chondrocytes

• structural support

• Compact bone

Trabecular Matrix Formation

• Osteoblasts deposit osteoid onto remnants of calcified cartilage

• Calcified cartilage acts as a scaffold for early bone spicules

• Spicules enlarge and connect → trabeculae

• Trapped osteoblasts → osteocytes

• Trabeculae are remodeled into mature cancellous bone

Osteocytes

• Mature bone cells that maintain and monitor bone

• Develop from osteoblasts that become trapped in mineralized bone matrix

• Live in small spaces called lacunae

Zones of Bone growth

• Reserve Zone

• Proliferative Zone

• Hypertrophic Zone

• Calcification Zone

• Ossification Zone

Reserve Zone

• Secures the epiphyseal plate to osseous tissue of the epiphysis

• Region closest to the epiphyseal end of the plate

Proliferative Zone

• Produce new cartilage- that pushes epiphysis away from the diaphysis

• Chondrocytes divide rapidly

Hypertrophic Zone

• Older chondrocytes enlarge

• Chondrocytes mature

• Matrix between cells becomes thinner

Calcification Zone

• Cartilage matrix calcifies; nutrient diffusion decreases

• Chondrocytes die

• Calcified cartilage matrix remains as a scaffold

Ossification Zone

• Blood vessels invade

• Osteoprogenitor cells > Osteoblasts

• Osteoblasts deposit osteoid on calcified cartilage

• New bone forms

Flexion

Decreases the angle between two bones

Extension

Increases the angle between two bones

Abduction

Moves a body part away from the median plane

Adduction

Moves a body part toward the median plane

Rotation

Turns a bone around its longitudinal axis

Circumduction

Moves the limb in a circular pattern by combining flexion, extension, abduction, and adduction

Agonist

Primary muscle producing the movement

Antagonist

Produces the opposite movement

Synergist

Assists the agonist

Fixator

Stabilizes a bone or joint

Muscle tissue contains what contractile proteins?

• Actin

• Myosin

Parallel Fibers

Run parallel to the long axis of the muscle, generally in the same direction of the tendon

Fusiform

Thick rounded bells with tapered ends

Unipennate

Attach at angle to one side of tendon

Bipennate

Attach at an angle to both sides of central tendon

Multipennate

Attach at multiple angles to multiple tendon branches

Circular Smooth Muscle

Aids in constriction and narrowing of lumen

Longitudinal Smooth Muscle

Contracts to shorten the organ

Smooth muscle cells contract when it receives a signal from?

Autonomic Nervous system

Smooth Muscle Cells communicate via?

Gap Junctions

Sarcolemma

Plasma membrane that depolarizes during contraction

Sarcoplasmic reticulum

Membrane that surrounds myofibrils to store and release calcium

T-Tubules

Inward folds of sarcolemma that carry electrical signals deep into the cell

Excitation

An electrical signal travels to and through the muscle fiber from the nervous system

Contraction

Calcium allows myosin to bind actin > actin slides past myosin > sarcomere shortens

Relaxation

Calcium returns to the sarcoplasmic reticulum, and ATP allows myosin to release actin

Action potential

Will travel along the cell membrane (sarcolemma), down T tubules, and trigger calcium release from the sarcoplasmic reticulum

Acetylcholine

Neurotransmitter that triggers an action potential along the sarcolemma