Connective Tissue

unlike the other tissues that are defined by their cells, how is collagen defined?

by its environment

what is the most abundant type of tissue by weight

connective tissue

what is the major protein found in connective tissue and in the body in general

collagen

what are the functions of connective tissue

• binds structures- holds epithelial tissue, anchors basement membrane, holds skin onto rest of body

• provides support and protection

• serves as framework: skeleton, which attaches to other muscles and bones

• fills spaces

• stores fat

• produces blood cells

• protects against infection (white blood cells)

• helps repair damaged tissue (with blood supply)

are the cells in connective tissue as close as they are in epithelial tissue?

no, more spaced apart

what is in the extracellular matrix between cells in connective tissue?

protein fibers, ground substance (attracts water), and fluid (water)

can ALL connective tissues divide

mostly

how does the blood supply vary in connective tissue?

• some are vascular, bone for example has a very good blood supply so if it’s damaged, it can heal quickly

• other places like ligaments and tendons are avascular, so because they have no blood supply it takes very long to heal

can cartilage repair itself?

no, since it’s avascular

what are types of fibers

collagen, elastin, and reticular

what is ground substance

it’s mostly water, proteins, and sugar molecules that fill the spaces around cells and fibers. it binds, supports, and provides a way that substances can transfer between blood and cells

what is the consistency of the extracellular matrix like?

carries from fluid (blood), semi-solid (areolar), to solid (bone)

what are fixed cells?

cells that dont move

what is the most common fixed cell?

fibroblast

what is the shape of fibroblasts and what does it do?

star shaped. produces protein fibers (collagen and elastin)

what are mast cells?

• usually located near blood vessels

• release heparin (blood thinner) and histamine (allergic response)

what major cell type are macrophages?

wandering cells

describe macrophages function

(originate as white blood cells)

-specialize in phagocytosis: wander for stuff to eat such as an embolus. when u get a cut, a signal gets macrophages to come over.

Collagenous fiber

• thicks threads of proteins (collagen) that run in parallel bundles.

• major structural protein of body that is flexible (NOT stretchy) that is found in skin, bone, and cartilage. Is white

Elastic fibers

• thin proteins-elastin.

• stretchy and easily retain shape

• yellow

• in vocal cords. the amount of elastin changes your tone (hence why smokers have a croaky voice and wrinkles bc of their elastin decrease)

reticular fibers

• THIN collagen fibers (so like a type of collagen)

• delicate

• branched framework

• supporting mesh in soft tissues like spleen, bone marrow, and the tissues and organs of the lymphatic system

what are the 3 major categories of connective tissue?

1. connective tissue proper

2. dense connective tissue

3. specialized connective tissue

what are the 3 types of connective tissue proper?

areolar, adipose, and reticular

areolar

• cobweb like and delicate

• most widely distributed

• contains mainly fibroblasts that r separated by a gel-like matrix (which includes gel-like ground substances, collagen, and elastin)

• beneath layers of epithelium and binds skin to organs

• many nourishing blood vessels

Adipose tissue or fat

• develops when adipocytes form fat droplets/oil droplets in their cytoplasm, like take up most of each cell

• insulation, kidneys, heart, eyeballs

• cushions joints and organs

• in adipose tissue, there are clusters of adipocytes. in the background is spots of ground substance

white fat

stores nutrients to be used for energy

brown fat

break down nutrients to produce heat

Reticular connective tissue

• thin reticular fibers, providing mesh

• provide framework for organs like livers and spleen (don’t need to know structure)

what are the 3 types of dense connective tissue

dense regular, dense irregular, and elastic connective

where is dense regular found?

tendons and ligaments

where’s dense irregular found?

dermis of skin

what does dense irregular allow for?

tissue to sustain tension exerted from many directions

elastic connective

• consists of mostly elastin fibers

• attaches things like bone

dense regular connective tissue

• few cells, mostly fibroblasts

• packed collagenous fibers with fine network of elastic fibers to withstand pulling forces

• poor blood supply

• image looks like a bunch of collagen fibers, with cells smushed between them

cartilage

• lacks direct blood supply

• support, framework, and attachment

• cartilage cells are chondrocytes, and each chondrocyte is within a lacunae

what are the 3 types of cartilage?

1. hyaline cartilage

2. elastic cartilage

3. fibrocartilage

Hyaline cartilage

• most common type

• FINE collagenous fibers (why the lab just looks like a green background, bc they’re too small to see individually)

• white and glassy

• ends of bone, soft part of nose, front of ribcage, fetal skeleton

• in the tissue, there are kind of clumps or chondrocytes, WITH lacunae (with spots of ground substance in the back as well)

Elastic cartilage

• dense network of elastic fibers, the chondrocytes are like within that

• like hyaline cartilage, random placement of chondrocytes and their lacunae, sometimes in groups

• background is ground substance

• external part of ear

Fibrocartilage

• many collagen fibers-tough

• shock absorber for structures with pressure like spine and knee

• kinda looks similar to dense connective tissue, except they’re not squished, (and obvi the lacunae exsist)

why is bone so hard? why does it HAVE to be hard

mineral salts and collagen. has to support body structures and protect organs, as well as being an attachment point for muscles. note that collagen makes it not completely brittle

what are bone CELLS called?

osteocytes

how are osteocytes a bit similar to chondrocytes

both are in lacunae

structure of bone cell

• each unit is an osteon

• in the middle of an osteon is the osteonic canal, where the blood supply is

• because the osteocytes are stuck in the lacunae and can’t move, gap junctions called canaliculli branch out towards the osteonic canal

blood

• transports substances

• homeostasis maintaining

• tissue is composed of formed elements (which is within a fluid matrix)- red blood cells, white blood cells, and platelets

• blood fluid matrix is plasma

• NO fibers