1 Histology

Vocabulary Words – List #2 1. histology – the study of tissues 2. tissue – layers or groups of similar cells with a common function 3. squamous – flat 4. stratified – layered 5. pseudo- - fake 6. cilium – slender, motile cellular process 7. microvillus – tiny, cylindrical extension of the cell membrane that increases surface area 8. mucus – thick fluid secretion that coats and protects 9. serous – serum-like; watery 10. secrete – to produce and release a substance

3 Histology - the study of tissues Tissue – layers or groups of similar cells with a common function There are four (4) primary or major tissue types: 1. Epithelial Tissue 2. Connective Tissue 3. Muscle Tissue 4. Nervous Tissue Introduction - Histology

4 Intercellular Junctions 1. Tight junctions – “stitching” Closes the space between cells Located among cells that form sheet-like layers that line surfaces Location: Blood brain barrier, lining of small intestine 2. Desmosomes – “spot welds” Form “spot welds” between cells to form reinforced structural unit Location: outer skin cells 3. Gap junctions - “tubes” Tubular channels between cells that allow passage of ions and nutrients between cells Location: cardiac muscle cells Tight junction Cell membrane Desmosome Gap junction

5 General characteristics: Covers the body surface and organs, lines body cavities and inside of hollow organs, ducts and vessels Apical surface – exposed to open space; Basal surface – attached to a Basement membrane – thin, non-living layer that anchors epithelium to underlying connective tissue Avascular (no blood vessels) – nutrients diffuse to epithelium from underlying connective tissue, which is very vascular. Cells readily divide, so injuries heal rapidly Cells tightly packed, to form protective barriers (outer layer of skin, lining of the mouth) Functions - protection, secretion, absorption, and excretion Classified according to cell shape and number of layers of cells Epithelial Tissue

6 Simple squamous: Single layer of flat cells Substances pass through easily by diffusion Line alveoli (air sacs in the lungs) Line blood vessels & lymphatic vessels ; line serous membranes Simple cuboidal: Single layer of cube-shaped cells Line kidney tubules (secretion & reabsorption) Line ducts of some glands (secrete glandular products) (b)(a) Free surface of tissue Simple squamous epithelium Basement Nucleus Connective tissue b,d: © Ed Reschke Nucleus Basement membrane Free surface of tissue Simple cuboidal epithelium Connective tissue Lumen (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

7 Simple columnar: Single layer of elongated cells Nuclei near the basement membrane at same level Some have cilia (movement of material across surface of cell) Some have microvilli (absorption) Often have goblet cells (secrete mucus) Line uterus, stomach, intestines Pseudostratified columnar: Single layer of elongated cells Nuclei at various levels, giving a stratified appearance Often have cilia Often have goblet cells Line respiratory passageways Nucleus Basement membrane Microvilli (free surface of tissue) Connective tissue Mucus Cytoplasm Goblet cell (a)(b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer. (a)(b) Cilia (free surface of tissue) Goblet cell Basement membrane Nucleus Connective tissue Cytoplasm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Epithelial Tissue

8 Stratified squamous: Many cell layers – provides protection Top cells are flat Outer layer of skin – accumulates keratin Also lines oral cavity, esophagus,vagina, and anal canal Stratified cuboidal: 2-3 layers of cube-shaped cells Protection Lines ducts of mammary glands, sweat glands, salivary glands, and the pancreas Basement membrane Layer of dividing cells Connective tissue Free surface of tissue Squamous cells (b)(a) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer (a)(b) Stratified cuboidal epithelium Free surface of tissue Lumen Basement membrane Connective tissue Nucleus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer. Epithelial Tissue

9 Stratified columnar: Top layer of elongated cells Cube-shaped cells in deeper layers Lines part of male urethra and part of pharynx Transitional: Many cell layers Cube-shaped and elongated cells Can stretch in response to increased tension, forming an expandable barrier Inner lining of urinary bladder, ureters, and urethra (b)(a) Lumen Stratified columnar epithelium Connective tissue Basement membrane Free surface of tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Al Telser, photographer Stretched transitional epithelium Basement membrane Underlying connective tissue Basement membrane Underlying connective tissue Unstretched transitional epithelium (b)(a) (d)(c) Free surface of tissue Free surface of tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b,d: © Ed Reschke Epithelial Tissue

10 Glandular Epithelium Composed of cells that are specialized to produce and secrete substances Adeno – “Gland” (Gk. – “acorn”) There are two (2) types of glands: Endocrine glands are ductless (key word: hormone) – secrete directly into blood Exocrine glands – secrete their products into ducts that open onto a surface (such as the skin or the lining of the digestive tract) Unicellular exocrine gland: Composed of one cell Example: Goblet cell Multicellular exocrine gland: Composed of many cells Sweat glands, salivary glands, etc. Simple and compound

11 Structural Types of Exocrine Glands Duct Secretory portion Tissue surface Simple tubular Simple branched tubular Simple branched alveolar Simple coiled tubular Compound tubular Compound alveolar Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

12 Types of Glandular Secretions Merocrine Glands Fluid product released by exocytosis Salivary glands Pancreas gland Sweat glands Apocrine Glands Portion of cell pinches off during secretion Mammary glands Ceruminous glands Holocrine Glands Whole cells filled with secretory product released Sebaceous glands (a) Merocrine gland(b) Apocrine gland(c) Holocrine gland Secretion Pinched off portion of cell (secretion) Intact cell Disintegrating cell and its contents (secretion) New cell forming by mitosis and cytokinesis

Carcinoma Read about carcinomas (pg. 150). What percentage of all human cancers are carcinomas? From which type of tissue do carcinomas originate? What does this observation suggest about the more common carcinogens (cancer-causing agents)? 13

NAME THE EPITHELIUM (8 slides)

1. 1. Stratified Cuboidal

2. Simple Squamous

3. Simple Cuboidal

4. Stratified Columnar

5. Stratified Squamous

6. Simple Columnar

Note the difference between a villus and microvillus (plural = microvilli). Villus

7. Transitional Epithelium

8. Pseudostratified Columnar Epithelium

Which type of cellular junction is a tubular junction that allows the passage of ions and nutrients between adjacent cells? Gap junction In what type of tissue are gap junctions found? Cardiac muscle

Which type of cellular junction looks like stitching, closes the space between adjacent cells, and is found in epithelium that form lining? Tight junction Which type of cellular junction forms “spot welds” between cells and helps to form a reinforced structural unit? Desmosome

What are some characteristics that all epithelial tissue have in common? Have a free surface, a basement membrane, tightly packed, avascular, divide often. Where are they found? Lining body cavities and the inside of hollow organs, ducts and vessels, cover surface of organs

What are the 4 main functions of epithelial tissue? Protection, absorption, secretion and excretion How are epithelial tissues classified? According to cell shape and the number of cell layers

Which type of epithelium is a single layer of flat cells? Simple squamous Where can it be found? Lines the alveoli (air sacs) in the lungs, lines blood vessels and lymphatic vessels What is an important function of simple squamous epithelium? Diffusion of gases and other materials (substances can quickly pass through)

Which type of epithelium lines the kidney tubules and the ducts of some glands? Simple cuboidal What is its function in the kidneys? Secretion and reabsorption What is its function in the ducts of glands? Secretion of glandular product

Which epithelium lines the uterus, stomach and intestines? Simple columnar What do the cells lining the small intestine have on their exposed surface? Microvilli What is the function of microvilli? Increase surface area of the cell for absorption of nutrients

What is a villus (plural = villi)? A tiny, finger-like projection of the inner lining of the small intestine What is its function? To greatly increase the surface area of the small intestine for absorption of nutrients What is a microvillus (plural = microvilli)? A hair-like extension on the exposed surface of a cell What is its function? Increases the surface area of the cell for absorption

Note the difference between a villus and microvillus (plural = microvilli). Villus

What are goblet cells? Unicellular (one cell) exocrine glands In what type of epithelia are they often found? Simple columnar and pseudostratified columnar What do they secrete? Mucus What is the function of mucus? Protection

What type of epithelium lines the airways (trachea, bronchi & bronchioli)? Pseudostratified columnar What do these cells have on their exposed surface? Cilia What is their function? To move the mucus that coats the surface away from the lungs and to the mouth. What is the purpose of the mucus? Cleans the inhaled air by trapping dust and other particles

What type of epithelium forms the outermost layer of skin and lines the oral cavity, esophagus, vagina and anal canal? Stratified squamous What is its function? Protection

What is keratin? A tough, waterproof protein In which type of epithelium is it found? Stratified squamous epithelium that forms the superficial layer of skin

Where in stratified squamous epithelium is keratin found? The outermost layers of flattened, dead cells What is its function? To provide a tough, waterproof barrier that protects underlying tissue from the external environment and to help prevent fluid loss

Which type of epithlium lines the larger ducts of salivary glands, sweat glands, mammary glands and also lines ovarian follicles and the seminiferous tubules in the testes? Stratified cuboidal What is the function? Protection (layering provides more protection) and secretion

Which type of epithelium lines the male urethra and part of the pharynx? Stratified columnar What is its function? Protection and secretion

Which type of epithelium has many layers of cube-shaped and elongated cells, and can change in response to increased tension? Transitional epithelium Where is it located? Inner lining of the urinary bladder, ureters and urethra

Which type of epithelium is composed of cells that are specialized to produce and release, (secrete), substances? Glandular epithelium What are the 2 main types of glands? Endocrine glands & exocrine glands

What are endocrine glands? Glands that secrete their product directly into the blood or tissue fluid. They are ductless. What are exocrine glands? Glands that secrete their products into ducts that open onto a surface (such as the skin, or the lining of the digestive tract)

What are the two types of exocrine glands? Unicellular (one cell) glands and Multicellular glands What is an example of a unicellular exocrine gland? Goblet cell What are some examples of multicellular exocrine glands? Salivary g., mammary g., sweat g., sebaceous g.

What type of secretion is thin and watery? Serous secretion Serous fluid is secreted by the serous membranes that line organs and body cavities (pleura, peritoneum, and pericardium). What is its function? Lubricates and moisturizes

What type of secretion is thick and viscous, (pronounced ‘viskus’)? Mucus What is the function of mucus? Protection

Which type of exocrine gland releases a fluid product by exocytosis? Merocrine gland What are some examples? Salivary g., sweat g., pancreas

Which type of gland pinches off a portion of the cell during secretion? Apocrine gland What are some examples? Mammary g. (milk), ceruminous g. (ear wax in external ear canal)

Which type of exocrine gland releases whole cells filled with the secretory product? Holocrine gland What is an example? Sebaceous gland (in skin – associated with the hair follicle)

Identify each type of gland 52 AM A. Merocrine gland B. Apocrine glandC. Holocrine gland