Unit 7 - Histology

a group of cells with similar structure and fcn

1. Nervous tissue (brain, spinal cord, nerves)

2. Muscle tissue (skeletal, cardiac, smooth)

3. Epithelial tissue (Lines Gi tract & other hollow organs, skin surface)

4. Connective tissue (Bones, tendons, fat & other soft padding)

An extracellular fluid called interstitial fluid -- which is mostly water and ions

Tight junction

- Points of contact between adjacent cells in seen epithelial tissue, some nervous and muscle cells

- formed by cell membrane proteins

Tight, anchoring (i.e. desmosomes), and gap junctions

Gap junction

Desmosomes/anchoring junction

- partial fusion of specific proteins on the lateral surface of the cell membrane that forms a ring like tight seal

The tight junction

Anchoring junction

- Proteins that fasten cells to each other and/or extracellular material

Anchoring junction/desmosomes

- has open channels formed by proteins through adjacent cell membranes (connecting their cytosols)

- allows ions/small molecules to pass between the cells

this allows cells to work as a unit (important for synchro of contractions in cardian and smooth muscles)

- stop integral proteins from moving between the apical and basolateral surfaces of the cell

Gap junction

- has one free surface

- little extracellular space between cells

- avascular (no blood vessels)

- basement membrane (attaches epithelium to underlying connective tissue layer)

First name (based on layers):

- if one layer (simple), if more (stratified)

Last name (based on shape, look at top layer to categorize):

- flattened (squamous), round/cubed (cuboidal), rectangular (columnar)

doesn't apply if the cells form a secretion gland

- only one layer of cells

- allows exchange of molecules (gasses, nutrients, ions)

- simple squamous (lungs), simple cuboidal (kidneys), simple columnar (stomach, small intestine)

The outer most layer of skin on your body

- more than one layer of cells

- protective of areas of abrasion (main fcn)

- predominant subtype is stratified squamous, which is apical cells squished (epidermis of skin)

- protection (our skin is protection, stratified squamous)

- secretion (glandular epithelium)

- Allows selective passage of materials (nutrients, waste, water, ions) across membranes (typically this is simple epithelia)

Stratified squamous, here's surface view

- 1 layer of columnar cells that appear stratified, bc some cells are shorted/nuclei appear at different levels. But all cells sit on basement membrane so its simple

- lines most of respiratory tract

- cell shape and layers vary because of stretching

- Only exists in inner lining of urinary system

- cuboidal to squamous when stretched

- used for secretion (so no longer in naming convention)

- the epithelial cells form a gland

subtypes: exocrine (substance) and endocrine (hormones) glands

- secret products onto body surfance or into cavity

can be:

- Unicellular, (secrete mucus into cavity, in digestive, reproductive, and respiratory tracts) e.g. goblet cells

- Multicellular, secretory and duct cells (ducts connect secretions to surface or cavity) e.g. sudoriferous (sweat glands), sebaceous (oil)

Unicellular exocrine gland, of glandular epithelium tissue

Multicellular exocrine gland, of glandular epithelium tissue

Endocrine (ductless)

- mainly supports and connects tissues

- the cells are far apart and separated by extracellular matrix (which usually forms the bulk of the tissue

the extracellular matrix gives connective tissue (CT) subtypes their identifying characteristics

- variable vascularity

CT cell types ending in:

-blast (create the matrix, e.g. osteoblast)

-cyte (maintain the matrix, e.g. osteocytes)

-clast (break down the matrix, e.g. osteoclast)

1. Fibres (proteins)

- collagen fibres for strength, elastic fibres for containing elastin (allow stretch and recoil), reticular fibres to form networks (e.g. the connective tissue part of basement membrane)

2. ground substance

- water (ISF) and large organic molecules (proteins & carbohydrates) surrounding cells and fibres,

Connective tissue proper (loose and dense ct), cartilage, bone, blood

cells: fibroblasts/fibrocytes (except adipose tissue, then adipocytes)

1. loose connective tissue

2. Dense connective tissue

1. areolar connective tissue

- loosely arranged collagen and elastin fibres, highly vascular

2. Adipose connective tissue

- very little matrix, large cells (adipocytes) store triglycerides, highly vascular and looks like chicken wire

- many fibres (so known as fibrous ct), little ground substance, poorly vascular

1. dense regular connective tissue

-collagen fibres running in same direction (e.g. ligaments which connects bone to bone

2. dense irregular connective tissue

- collagen fibres arranged irregularly (e.g. dermis of skin)

- large amounts of matrix

- made of fibres (collagen & elastin) and a ground substance of water

- Avascular

- 3 types: hyaline cartilage, elastic cartilage, fibrocartilage

Chondrocytes (located in cavities in the matrix called lacunae) and chondroblasts

1. hyaline cartilage (most abundant, at ends of long bones (like ribs) to reduce friction)

2. elastic cartilage (can recoil and maintain shape, e.g. ear pinna)

3. fibrocartilage (high in collagen fibres, work as shock absorbers)

osteocytes (in lacunae), osteoblasts, osteaclasts

- large amounts of matrix

- fibres have abundant collagen

- ground substance of inorganic calcium (Ca++), phosphate salts, and organic components (proteins & carbohydrates) make it rigid

- very vascular

- fluid connective tissue

- cells: red blood cells, white blood cells, platelets

- extracellular matrix is called plasma which contains soluble fibres (e.g. fibrinogen for blood clotting) and ground substance is mostly water with ions and proteins

- Contractile tissue

- subtypes: skeletal, cardiac, smooth

1. skeletal (striated, and a voluntary muscle)

2. cardiac (striated, and involuntary muscle)

3. smooth (non-striated, cant contract, its around arteries and organs)

- neurons (which conduct electrical impulses)

- glial cells (support and protect neurons)

- some CT: Cartilage,

- epithelia

- nervous tissue

- skeletal &smooth muscle tissue

- some CT: loose connective tissue (dense is very poorly vascular), bone, blood