Connective and Musculoskeletal Tissue and Macromolecules and Cell Types

Primary functions of the musculoskeletal system

• supporting the body

• allowing motion

• protecting vital organs

3 types of muscle

• skeletal

• cardiac

• smooth

skeletal muscle

muscle responsible for body movement

cardiac muscle

heart muscles (non-musculoskeletal)

smooth muscle

controls flow of substance in the body

5 kinds of bone

• long

• short

• flat

• irregular

• seamoid

musculoskeletal tissue types

• fascia

• tendons

• ligaments

• joints

fasciae

connect muscle to muscle

tendons

connect muscle to bones

ligaments

connect bones to bone

joints

connect individual bones; created by ligaments

connective tissue

group of tissues that maintains the form of the body and its organs and provides cohesion and internal support

what connects the muscular and skeletal system?

connective tissue

connective tissue cells

• fibroblast

• chondroblast

• osteoblast

fibroblast

produces protein collagen and elastin from amino acid pool

chondroblast

produces cartilage

osteoblast

produces bone, activated by vitamin D

2 main components of the ECM

extracellular fibers and ground substance

4 macromolecule families the ECM consists of

• proteins

• proteoglycans

• glycoproteins

• mineral crystals

What is the function of the extracellular matrix?

stabilize fibers and cells

fixed cells

• melanocyte

• fixed macrophage

• mast cells

• fibroblasts

• adipocytes

melanocyte

fixed pigment cell that synthesizes melanin, a brownish-yellow pigment

fixed macrophage

stationary phagocytic cell that engulfs cell debris and pathogens

mast cells

fixed cells that stimulate stimulate local inflammation and mobilize tissue defenses

fibroblasts

fixed cells that synthesize the extracellular fibers of the connective tissue

Fibers

• reticular fibers

• collagen fibers

• elastic fibers

reticular fibers

very thin type of collagen, forms mesh network around cells and supports small structures (ex capillaries, nerve fibers)

collagen fibers

thick, straight, or wavy, and often form bundles; very strong and resistant stretching (ex tendons, ligaments)

elastic fibers

made up of elastin, slender, unbranching, and very stretchy; recoil to their original length after stretching or distortion

wandering cells

• plasma cell

• free macrophages

• mesenchymal cells

• neutrophils and eosinophils

• lymphocytes

plasma cell

an active, mobile immune cell that produces antibodies

free macrophages

wandering phagocytic cells that patrol the tissue, engulfing debris or pathogens

mesenchymal cells

mobile stem cells that participate in the repair of damaged cells

neutrophils and eosinophils

small, mobile, phagocytic blood cells that enter tissues during infection or injury

lymphocytes

mobile cells of the immune system

ground substance

fills the space between cells and surrounds connective tissue fibers in all forms of connective tissue; serves as a filter and is clear, colorless, and viscous due to presence of proteoglycans and glycoproteins

Proteins (ECM)

primarily structural aid but also provide communication mechanism to cells; chains of individual amino acids

elastin

composed primarily of glycine, proline, valine, and alanine

collagen

composed primarily of glycine and proline but requires vitamin C to be synthesized

proteoglycans (ECM)

functions with proteins as structural ad; serves as barrier to bacteria and filter of microorganisms

glycoproteins (ECM)

connect proteins and proteoglycans; aid in stabilitym

mineral crystals

stabilize bones by solidifying ground substance; mostly calcium and phosphorous crystals

extracellular fiber types (ECM)

• collagen fiber

• elastic fiber

• reticular fiber

elastic fiber

made up of elastin, stretches and returns to original shape after stretching

5 Connective Tissue Types

• loose connective tissue

• dense connective tissue

• cartilage

• bone

• blood

adipose tissue

located deep in the skin, provides padding, cushions shocks, insulates, and stores energy reserves

reticular tissue

located in the kidney, liver, spleen, lymph nodes, and bone marrow, provides supporting framework

dense connective tissue

form, strong, and flexible; mainly made of collagen fibers with few cells (ex ligaments and tendons)

irregular dense connective tissue

makes up membranes that cover organs

regular dense connective tissue

serves to maintain posture, stability, and structure of the body (tendons/ligaments)

elastic connective tissue

serves to support with extra flexibility, more elastic in the body than irregular or regular CT; found in vocal cords and blood vessel walls

cartilage

maintains structures and provides some flexibility, absorbs shock and reduces friction; specialized matrix traps water to crate a gelhy

hyaline cartilage

tough and translucent; covers end of long bones

fibrocartilage

firm and rigid; between vertebrae and in knee joint

elastic cartilage

stretchable, easily returns to form; outer cartilage

bone

contains osteoblasts and osteocytes, extracellular matrix is solid/hard, contains collagen fibers

what controls the formation of mineral crystals in bone?

vitamin D

why is the bone ECM solid and hard?

due to mineral crystals of calcium and phosphorus

blood

transports substances to various parts of the body, provides immune system function (supports inflammatory response to injury)

is the blood ECM solid or liquid?

liquid; allows for easy flow between cells, composed entirely of plasma, lacks both fibers and ground substances

3 substages of phase 1

• inflammatory phase

• repair/proliferation phase

• remodeling phase

inflammatory phase

beginning of healing, separates area for repair; starts from the onset of injury and lasts a few days

repair phase

cell proliferation, beginning of tissue regeneration; starts 2nd or 3rd day and lasts 2-4 weeks

remodel phase

cell/tissue replacement, completion of regeneration; starts 2nd or 3rd week and lasts 6-18 months

bone repair

• osteoblast formation begins soon after initial injury

• cartilaginous callus is formed which will provide initial stabilization, though soft and weak initially

• chondrocytes grow, proteases degrade collagen of the callus and mineralization is initiated

• angiogenesis starts to form new vasculature which infiltrates new bone

• bone remodeling

cascade of events following injury

• cells release prostaglandins upon injury

• prostaglandins direct cell response

• cells clear debris

• active cells produce and secrete cytokines

• cytokines maintain or suppress cell response

• prostaglandins initiate cell and vessel proliferation

• growth factors and hormones direct and maintain tissue regeneration

Length of the inflammatory phase

3-5 days

cells involved in the inflammatory phase

• platelets

• mast cells

• neutrophils

• monocytes

• macrophages

platelets (inflammatory phase)

form a clot to wall-off injured tissue and allow fluid and cell accumulation

mast cells (inflammatory stage)

promote vasodilation and vessel permeability

neutrophils and macrophages (inflammatory phase)

migrate to the site to engulf and destroy damaged cells

length of repair phase

2-4 weeks

cells in the repair phase

• phagocytes

• fibroblasts

• osteoblasts

• osteoclasts

• chondrocytes

what happens to phagocytic activity during the repair phase?

slows down to near nothing

what do fibroblasts do during the repair phase?

release growth factors and induce angiogenesis

how long does the remodeling phase last?

6-18 months

major cells in the remodeling phase

• fibroblasts

• osteoblasts

• osteoclasts

• chondrocytes

• epithelial cells