Unit 7 - Histology (Tissues)

What is histology?

• The study of tissues

What is a tissue?

• A group of cells with similar structure + function

What is interstitial fluid? (1.1)

• An extracellular fluid made of mostly water and ions

  • surrounds cells of most tissues

What are the 4 major tissue types?

• Epithelial Tissue

• Connective Tissue

• Muscle Tissue

• Nervous Tissue

What are cell junctions? (1.1)

• Points of contact between adjacent cells

  • Seen in epithelial tissue, some nervous and muscle cells

What are cell junctions formed by?

• Cell membrane proteins

What are examples of cell junctions? (3)

• Gap junctions

• Anchoring junctions (Desmosomes)

• Tight junctions

What are tight junctions? (1.1)

• Partial fusions of specific proteins on the lateral surface of the cell membrane

  • From a ring-like tight seal

What are the functions of tight junctions? (2)

• Prevents material from passing between cells

• Stops integral proteins from moving between apical and basolateral surfaces of the cell

What is the apical?

• Lumen exposed surface

What does basolateral mean?

• Attached

What are anchoring junctions (desmosomes)?

• Proteins that fasten cells together or to extracellular material

What are gap junctions? (1.1)

• Open channels (formed by proteins) through the adjacent cell membranes interconnecting the cytosols of the cells

  • = tissues can then work as a unit

What are the functions of gap junctions?

• Allows ions/small molecules to pass from one cell to another

Where are gap junctions important? (2)

• Cardiac + smooth muscle tissue (allows synchronization of contractions)

• Epithelial tissue

What is epithelial tissue?

• Lining tissue

What is connective tissue?

• Connecting tissue

What is muscle tissue?

• Contractile tissue

What is nervous tissue?

• Sensation and signalling tissue 

What is the function of epithelial tissue? (2)

• Covers body surface (skin)

• Lines body/organ cavities

What is lumen?

• Organ cavity

What are the characteristics of epithelial tissue?

• Has one free surface

• Little extracellular space between cells

• Avascular 

• Has a basement membrane

What does avascular mean?

• No blood vessels

What is the basement membrane? (2.1)

• Extracellular layer 

• Attaches epithelium to underlying connective layer 

  • form by both tissues + acts likes velcro

How is epithelial tissue classified? (1.2 + 1.3)

• # of cell layers sitting on basement membrane

  • simple - one layer

  • stratified - more than one layer

• Shape of the cells in apical layer

  • squamous - flattened

  • cuboidal - cube/round

  • columar - rectangular

What is the simple epithelia + function? (1.3)

• One layer

  • Allows exchange of molecules

  • Absorption

  • Secretion

What are the subtypes of simple epithelia? (3)

• Simple squamous

• Simple cuboidal

• Simple columnar

What is simple squamous epithelial tissue? (1.1)

• One layer of flat cells 

  • lungs

What is simple cuboidal epithelial tissue? (1.1)

• One layer of cube shaped cells

  • kidneys

What is simple columnar epithelial tissue? (1.1)

• One layer of column shaped cells

  • stomach, small intestine

What is the function of stratified epithelia?

• Protective (areas of abrasion)

What is stratified squamous epithelia?

• Apical cells squished

  • epidermis of skin

What is pseudostratified epithelia? (1.1)

• Columnar cells that appear stratified but all cells sit on the basement level → simple

  • some cells are shorter + nuclei appear at different levels

Where is pseudostratified epithelia found? (1.1)

• Lines most of respiratory tract where cells are also ciliated

  • = ciliated pseudostratified epithelium 

What is transitional epithelia? (1.2)

• Epithelia where cell shape + layering varies w/ stretching

  • Only in inner lining of urinary system

  • Cuboidal → squamous when stretched

What is the function of glandular epithelium?

• Secretion

What is glandular epithelium?

• Epithelial cells when they form a gland

What are subtypes of glandular epithelium? (2)

• Exocrine glands

• Endocrine glands

What are exocrine glands? (2.2)

• Secretes products → body surface or body cavity

• Can be:

  • Unicellular

  • Multicellular

What are unicellular exocrine glands? (1.1)

• Individual cells specialized for secretion scattered among other cells

• ex. goblet cells

What are multicellular exocrine glands? (1.1 +1)

• Consists of secretory and duct cells

  • ducts connect secretions to surface or cavity

• ex. sudoriferous (sweat), sebaceous (oil)

What are endocrine glands?

• Glands with no ducts

What is the function of endocrine glands? (2)

• Secretes hormones → ECF surrounding glandular cells

• Enters the blood plasma to transport to target cells/tissues

What are the functions of epithelia?

• Protection

• Secretion

• Allows selective passage of materials

What is the function of connective tissue?

• Mainly supports and connects tissues

What are the characteristics of connective tissue? (2)

• Cells far apart, separated by extracellular matrix (bulk of tissue)

• Variable vascularity

What are the connective tissue cell types?

• -blast

• -cyte

• -clast

What does the suffix -blast mean?

• Creates matrix

What does the suffix -cyte mean?

• Maintains matrix

What does the suffix -clast mean?

• Breaks down matrix

What is the connective tissue matrix composition? (2)

• Fibers (proteins)

• Ground substance

What are the fibres in connective tissue + their functions? (3)

• Collagen - strength

• Elastic - allow stretch and recoil

• Reticular - form networks

What is ground substance composed of + its function? (2)

• Surrounds cells + fibres

• Made of water (ISF, large organic molecules, proteins, carbohydrates)

What is connective tissue proper?

• Cells with fibroblasts/fibrocytes, EXCEPT adipose tissue

What are the types of connective tissue proper? (2)

• Loose connective tissue

• Dense connective tissue

What is areolar connective tissue? (1.2)

• Loose connective tissue 

  • Loosely arranged collagen + elastin fibres

  • Highly vascular

What is adipose connective tissue? (1.3)

• Loose connective tissue 

  • Very little matrix

  • Cells are large (adipocytes), store triglycerides

  • Highly vascular

What are the characteristics of dense connective tissue? (3)

• Many fibres 

• Little ground substance

• Poorly vascular

What are the types of dense connective tissue? (2)

• Dense regular connective tissue

• Dense irregular connective tissue

What are the characteristics of dense regular CT? (1.2)

• Collagen fibres running in the same direction

  • tendons + aponeuroses - muscle → bone

  • ligaments - bone → bone

What are the characteristics of dense irregular CT? (1.1)

• Collagen fibres arranged irregularly 

  • dermis of skin

What are the characteristics of cartilage? (1.2 + 1.2 + 1)

• Cells are:

  • chondrocytes (mature cartilage cells); located lacunae

  • chondroblasts (immature cartilage cells)

• Large amount of matrix:

  • fibres → collagen + elastin proteins

  • ground substance is mostly water; firm due to types of organic molecules present

• Avascular - heals slowly

What are lacunae?

• Cavities in the matrix

What are the types of cartilage? (3)

• Hyaline cartilage

• Elastic cartilage

• Fibrocartilage

What is hyaline cartilage? (1.1)

• Most abundant

  • ex. trachea, ribs, ends of bones

What is elastic cartilage? (1.1)

• Has many elastic fibres

  • epiglottis, ear pinna

What is fibrocartilage? (1.2)

• High in collagen fibres

  • “shock absorbers”

  • eg, intervertebral discs, pubic symphysis

What are the characteristics of bones? (1 + 1.2.3 + 1)

• Cells → osteocytes, osteoblasts, osteoclasts

• Matrix:

  • fibres - abundant in collagen

  • ground substance -

    • inorganic calcium (phosphate salts),

    • organic components (proteins and carbohydrates) that make it rigid,

    • little water

• Very vascular

What is blood?

• Fluid connective tissue

What is blood composed of? (1.3 + 1)

• Cells:

  • Red blood cells

  • White blood cells

  • Platelets

• Plasma - the ECM

What is plasma? (1.2)

• The extracellular matrix in blood:

  • Contains soluble fibres

  • ground substance: mostly water w/ ions, proteins

What are the muscle tissue subtypes? (3)

• Skeletal (striated)

• Cardiac (striated)

• Smooth (non-striated)

What are the cell types of nervous tissue? (2)

• Neurons

• Gilal 

What is the function of neurons?

• Conduct electrical impulses

What is the function of glial cells? 

• Support + protect neurons