Connective Tissue Chapter 4. Tissues

Components of connective tissues; what is found in it?

1. Specialized cells

2. Extracellular protein fibers (outside for integrity)

3. Fluid called ground substance

Matrix

consists of extracellular components of connective tissue (cells & fibers); extracellular material that surrounds cells

– Majority of tissue volume

– Determines specialized function

Functions of connective tissues

– Establishing a structural framework for the body

– Transporting fluids & dissolved materials

– Protecting delicate organs

– Supporting, surrounding, & interconnecting other types of tissue

– Storing energy reserves; especially triglycerides (fat/3fatty acids + glycerol backbone)

– Defending the body against microorganisms

Categories of connective tissues

1. Connective tissue proper

• Connect and protect

2. Fluid connective tissues

• Transport

3. Supporting connective tissues

• Structural strength

What kinds of Connective tissue proper are there, and their subcategories?

Loose connective tissue:

• Areolar

• Adipose

• Reticular

Dense connective tissue:

• Regular

• Irregular

• Elastic

What kinds of Supportive connective tissue are there, and their subcategories?

Cartilage:

• Hyaline

• Fibrocartilage

• Elastic

Bone:

• Compact Bone

• Spongy Bone

What kinds of Fluid connective tissue are there?

Blood & Lymph

Loose connective tissue

Connective Tissue proper; not as strong/loose/giggly

• More ground substance, fewer fibers

• Example: fat (adipose tissue)

• “Packing materials” keeps stuff where it needs to stay

• Fill spaces between organs, cushion cells, and support epithelia

Dense connective tissue

Connective Tissue proper;called collagenous tissues (more collagen fibers than LCT); greater strength & resistance;

• More fibers, less ground substance

• Example: tendons

What are the Cells of connective tissue proper? Cells that make it up/mechanism?

 Fibroblasts

 Fibrocytes

 Adipocytes

 Mesenchymal cells

 Melanocytes

 Macrophages

 Mast cells

 Lymphocytes

 Microphages

Fibroblasts

cell of connective tissue proper; (blast=makes)

– most abundant cell type

– Found in all types of connective tissue proper

– Secrete proteins and hyaluronan (cellular cement)

—makes the fibers

Fibrocytes

cell of connective tissue proper; (fiber cell)

– Second most abundant cell type

– Maintain connective tissue fibers

— made from fiber blast

Adipocytes

cell of connective tissue proper;

– Fat cells

– Each cell stores a single, large fat droplet

Mesenchymal cells

cell of connective tissue proper;

– Stem cells that respond to injury or infection; REPLACE & REPAIR

– can develop into other connective tissue cells, like fibroblasts, or macrophages (mainly), etc

Melanocytes

cell of connective tissue proper;

– Produce & store the brown pigment melanin (what makes us darker)

Macrophages

cell of connective tissue proper;

– Large phagocytic cells of the immune system

– Engulf pathogens and damaged cells; eaters of the bad

– Fixed macrophages stay in tissue

– Free macrophages migrate

Mast cells

cell of connective tissue proper;

– Stimulate inflammation after injury or infection

• Release histamine (dilator/increase blood flow/contract smooth muscle) and heparin (anticoagulant/blood thinner)

– Basophils are leukocytes that also contain histamine & heparin

Lymphocytes

cell of connective tissue proper;

– Migrate throughout the body

– May develop into plasma cells, which produce antibodies (immune cells)

Microphages

cell of connective tissue proper;

– Phagocytic small white blood cells (neutrophils, eosinophils)

-engulf & destroy bacteria and other foreign particles

– Attracted to signals from macrophages and mast cells

Connective tissue fibers

1. Collagen fibers

2. Reticular fibers

3. Elastic fibers

Collagen fibers

Connective tissue fiber;

– Most common fibers in connective tissue proper

– Long, straight, & unbranched

– Strong/tough & flexible

– Resist force in one direction

– Abundant in tendons & ligaments

Reticular fibers

Connective tissue fiber;

– Form network(mesh-like) of interwoven fibers (stroma)

– Strong & flexible

– Resist forces in many directions

– Stabilize functional cells & structures; (parenchyma; functional parts of an organ)

– Example: sheaths around organs (supports)

stabalizer

Elastic fibers

Connective tissue fiber;

– Contain elastin

– Branched and wavy

– Return to original length (quickly) after stretching

– Example: elastic ligaments of vertebrae

as older, elastic gets weaker

Ground substance

– Is clear, colorless, and viscous (thick)

– Fills spaces between cells and slows pathogen movement

-slows everything down, not allowing things to go through

Embryonic connective tissues

(not so imp.)

– Not found in adults

– Mesenchyme (embryonic connective tissue)

• First connective tissue in embryos

– Mucous connective tissue

• Loose embryonic connective tissue

Mesenchyme

embryonic connective tissue; First connective tissue in embryos; can develop into different types of connective tissue.

Types of loose connective tissues in adults

1. Areolar tissue

2. Adipose tissue

3. Reticular tissue

Areolar tissue

loose connective tissue;

– Least specialized

– Open framework; loose web like; Elastic fibers

– Viscous ground substance (absorbs shocks)

– Holds capillary beds

• Example: under skin (subcutaneous layer)

Adipose tissue

loose connective tissue; fat

– Contains many adipocytes (fat cells);in adults do not divide

– Expand to store fat

– Shrink as fats are released

• Mesenchymal cells divide and differentiate (stem cells that duplicate)

– May be removed (temporarily) via liposuction

WHITE FAT & BROWN FAT

Reticular tissue

loose connective tissue;

– Provides support

– Reticular fibers form a complex, 3-D mesh-like stroma (around organs)

– Support functional cells of organs

– Found in liver, kidney, spleen, lymph nodes, and bone marrow (soft)

What do Mesenchymal cells do in adipose tissue?

cells divide and differentiate;

– To produce more fat cells

– When more storage is needed

—eating more stims stem cells

White Fat

adipose tissue;

– Most common

– Stores fat and absorbs shocks

– Slows heat loss (insulation)

Brown Fat

adipose tissue;

– Found in babies and young children

– More vascularized

– Adipocytes have many mitochondria

– Breakdown of lipids releases energy and warms body

shiver=metabolize more fat

Dense Connective Tissue types

• Dense regular

• Dense irregular

• Elastic

Dense regular connective tissue

dense connective tissue;

– Tightly packed, parallel (strongest in 1 direction) collagen fibers

• Tendons = muscle to bone

• Ligaments= bone to bone & stabilize organs

• Aponeuroses are tendinous sheets that attach a broad, flat muscle to another structure (thin layers of fibrous tissue/like tendon but flat)

Dense irregular connective tissue

dense connective tissue;

– Interwoven network of collagen fibers; many directions

• Provides strength to dermis

• Forms sheath around cartilages (perichondrium) and bones (periosteum) IMPORTANT

• Forms capsules around some organs (e.g., liver, kidneys, and spleen);darker appearance

Elastic tissue

dense connective tissue;

– Made of elastic fibers

– allows to flex & return back to shape

• Example: elastic ligaments of spinal vertebrae

What do Connective tissues do?

1. Provide strength & stability

2. Maintain positions of internal organs

3. Provide routes for blood vessels, lymphatic vessels, & nerves

Fasciae

– Connective tissue layers & wrappings that support & surround organs

1. Superficial fascia

• Separates skin from underlying tissues

2. Deep fascia

• Sheets of dense regular connective tissue (& muslce)

3. Subserous fascia

• Lies between deep fascia & serous membranes that line body cavities

Blood

Fluid connective tissue;

– Has plasma; a watery matrix

– Has cells & cell fragments, known as formed elements:

• Red blood cells (erythrocytes); biocave/transport O2 & Co2

• White blood cells (leukocytes); immune response/by bad cells

• Platelets; fragments; helps w/ blood clotting

Lymph

Fluid connective tissue;

– Forms as interstitial fluid (found in) that enters lymphatic vessels; then gets returns to blood stream

– Monitored by immune system (part of)

– Returned to veins near the heart

Cartilage function & contents

Supporting connective tissues; undeveloped bone

• Function: Shock absorption + protection & keeps from rubbing bone to bone

• Matrix: Firm gel containing chondroitin sulfates

• Cells in matrix: Chondrocytes (found in lacunae (small chambers))

Cartilage structure

Avascular = no blood vessels; Chondrocytes release antiangiogenesis that prevent blood vessel growth

Perichondrium = covering around cartilage that supports it

(avascularity makes cartilage heal slowly)

Perichondrium

covering around cartilage; dense irregular tissue

Outer layer: support + protection

Inner layer: growth + maintenance

Types of cartilage

1. Hyaline cartilage

2. Elastic cartilage

3. Fibrocartilage

Hyaline cartilage

type of cartilage; smooth

– Most common type ***

– Tough/strong & somewhat flexible

– Reduces friction between bones (bone to bone)

– Found in synovial joints, rib tips, sternum, and trachea

Elastic cartilage

type of cartilage; flexible

– Supportive but bends easily (elastic fibers)

– Found in external ear and epiglottis

Fibrocartilage

type of cartilage;

– Very durable & tough

– Limits movement

– Prevents bone-to-bone contact

– Found around joints, between pubic bones, & between spinal vertebrae

Cartilage growth

– Interstitial growth

• Enlarges cartilage from within

– Appositional growth

• Growth at outer surface of cartilage

Bone

(osseous tissue);

• Supports body weight

• Calcified; Calcium salts make bone hard/rigid

• flexible Collagen fibers prevent shattering

• have osteocytes

• Periosteum covers bone

What is the periosteum?

covering around the outside of bone;

• Fibrous (outer) and cellular (inner) layers (support & protect)

A tough layer of Dense irregular connective tissue that covers the outside of bones

Osteocytes

in bone;

• bone cells that lie in lacunae (small spaces/chambers)

• Arranged around central canal (center of osteon) within matrix

Canaliculi

in bone;

• tiny channels in the bone matrix

• Allow exchange of materials between osteocytes and blood

Tissue membranes

– Physical barriers; outside covering made of tissues

– Line or cover body surfaces

– Consist of epithelium + connective tissue

Four types of tissue membranes

1. Mucous membranes

2. Serous membranes

3. Cutaneous membrane

4. Synovial membranes

Mucous membranes (mucosae)

tissue membranes;

– Line passageways that connect to the outside

– In digestive, respiratory, urinary, & reproductive tracts (passing of things)

– Epithelial surfaces must be moist; to reduce friction & to facilitate absorption/secretion

– Lamina propria is areolar tissue in mucous membranes

Serous membranes

tissue membranes;

– Line cavities that don’t open to the outside

– Thin but strong

– Parietal portion lines inner surface of cavity

– Visceral portion (serosa) covers the organs

– Serous fluid reduces friction

Cutaneous membrane

tissue membranes;

– Skin that covers the body

– Thick, relatively waterproof, & usually dry

— hardened materials

Synovial membranes

tissue membranes;

– Line synovial joint cavities

– Movement stimulates production of synovial fluid for lubrication

– Lacks a true epithelium

Lamina propria

layer of areolar connective tissue underneath the epithelium in mucous memebranes

Types of Serous membranes

1. Peritoneum

• Lines peritoneal cavity

• Covers abdominal organs

2. Pleura

• Lines pleural cavities

• Covers lungs

3. Pericardium

• Lines pericardial cavity

• Covers heart

What does areolar connective tissue always have over it?

Mesothelium in serous membranes; epithelial simple squamous

Compact Bone

• solid

• dense

• strong

• has osteons (structural units around central canal)

Spongy Bone

• cancellous bone

• sponge-like

• has spaces between trabeculae

• lighter than compact bone

• inside bones & ends of long bones

Connective tissue found in tendons?

Dense Regular connective tissue

Cartilage cells are?

Chondrocytes

What are the spaces containing cartilage cells called?

Lacunae

Which cartilage is found in intervertebral disc?

Fibrocartilage

What is the structural unit of compact bone?

Osteon