Epithelium Glands Types of Tissue Muscular Tissue Nervous

Epithelium & Glands

Types of Tissue Muscular Tissue Nervous Tissue Epithelial Tissue Connective Tissue

GI Tract (x-section) Covered by epithelium LUMEN Lined by epithelium

What Is Epithelium? Cells are in close apposition to each other Ø Demonstrate polarity Ø l Have a basement membrane Rapid cell turnover Ø No blood vessels Ø Variety of functions Ø l Absorption, secretion, protection, sensory perception, transportation

Types of Epithelium Note that epithelia become more complex and add layers (stratified)

Things are often found on top of cells as well Ø Microvilli Ø Cilia l Usually on pseudostratified Ø Stereocilia l Pseudostratified or columnar Ø Keratin l Stratified squamous

To start: Simple Squamous Epithelium § Transport (nutrient/gas exchange, molecules) § Lubrication of organ surfaces • Mesothelium – lines external surfaces (serosal surface) • Endothelium – lines internal surfaces (endothelium or mucosal surface)

Just this thin, one cell thick layer is the mesothelium Blood vessels such as capillaries and venules are made of simple squamous

Simple Cuboidal Epithelium This type of epithelium often forms ducts, tubules, & secretory cells as above in kidney

Simple Columnar Epithelium § Absorption (nutrients) § Secretion of mucus, enzymes, etc. § Protection

The different epithelia often add layers and become stratified such as here - Squamous Epithelium. This example from vagina does not have Keratin, so is Nonkeratinized (Use these descriptors!!!)

While this Stratified Squamous Epithelium is Keratinized –thick skin

Stratified Cuboidal Epithelium This type of epithelium Lines middle sized to large ducts and is therefore Often involved in Secretion/absorption (See, functional aspect)

Stratified Columnar Epithelium More often than not, it is found lining large ducts

Pseudostratified Columnar Epithelium § Often has cilia or stereocilia on surface § Protection, absorption, secretion § Not all cells reach the lumen, BUT §All cells touch the BM

Transitional Epithelium TRANSITIONAL BECAUSE THEY CHANGE THEIR SHAPE IN THE BLADDER

Glandular Epithelium Imagine an orange. The peel is the CT stroma, juicy segments are functioning cells (parenchyma) Stroma Parenchyma • Epithelial cells containing secretory granules Duct

Basic diagram to show disappearance of duct and thus formation of endocrine gland

Classification of Exocrine Glands Exocrine means ducts are involved. Not so in endocrine glands Based on: q Cell Number q Type of Secretion q Mode of Secretion

Unicellular Glands GOBLET CELLS § Nucleus in basal portion § Secretory droplets in apical portion

Multicellular Glands LINING OF THE STOMACH § Majority have ducts § Stomach is exception § Also classified by shape of secretory unit THIS LINING FORMS A NON-DUCTED, MULTICELLULAR EXOCRINE GLAND (STOMACH PROTECTION) These are NOT goblet cells

LOOK CLOSELY AND YOU CAN SEE THAT EACH LINING CELL CONTAINS MULTIPLE DROPLETS. THE GOBLET CELL CONTAINS ONE

The Acinus (Functional cell group) - FRUIT ANALOGY AGAIN. IMAGINE A BUNCH OF GRAPES. THE STALKS ARE THE DUCTS AND CT, THE CLUSTERS OF GRAPES FORM AN ACINUS. THE GRAPES THEMSELVES MAKE STUFF, THE PARENCHYMA

Types of Secreted Product Mucous Glands - clear Serous Glands (Peptides/proteins) -granular Seromucous Glands MIXED

Modes of Secretion Holocrine – Whole cell is secreted (sebaceous gla Merocrine – Just the Synthesized Product is released Apocrine – The product+ The top portion Of the plasma membrane is released

Endocrine Glands - steroids Cord Arrangement Follicular Arrangement

Endocrine Glands ENDOCRINE GLANDS DO NOT HAVE DUCTS, AS THE PRODUCT (HORMONES) IS RELEASED THROUGH THE BASE OF THE CELL INTO THE BLOOD SUPPLY, NOT ONTO A SURFACE LIKE EXOCRINE ENDOCRINE TISSUE WILL THEREFORE HAVE LOTS OF BLOOD VESSELS IN IT, WHILE THE EXOCRINE TISSUE WILL HAVE DUCTS AND CT. ENDOCRINE CELLS ARE ARRANGED IN CORDS OR CLUMPS ALONG AND AROUND VESSELS