Tissues: Living Communities

Learning Objectives List the four major tissue types Describe the functions of epithelial tissues –3 major types of cellular junctions found between epithelial cells –Describe the structure and purpose of basement membrane –Characteristics used to classify different epithelial tisse –Characteristics used to classify different glands List and describe the components of connective tissues –Differentiate between areolar, adipose, and reticular connective tissues –Dense regular, dense irregular, and elastic connective tissues –Differentiate between hyaline cartilage, elastic cartilage, and fibrocartilage –Bone –Blood List and describe the three types of muscle List the components of a neuron

Types of Tissues Tissues are classified into the following four primary types: 1. Epithelial tissue (covers and lines) 2. Connective tissue (provides support) 3. Muscle tissue (enables movement) 4. Nervous tissue (controls work)

1.Functions 2.Characteristics 3.Attachments 4.Basement Membrane 5.Surface features 6.Shapes 7.Layers Epithelial Tissues

Epithelial Tissues 1. Functions: coverSheets of cells that cover and line other tissues Protect underlying tissues and may act to filter biochemical substances May absorb, secrete, or excrete biochemical substances May play a role in the reception of sensory input

2. Characteristics of Epithelia  Each epithelial cell has an apical surface and a basal surface Apical surface faces the lumen or outside of the organ Basal surface faces the basal lamina and blood vessels  Lateral surfaces are connected to neighboring cells by junctional complexes.  Epithelial cells are avascular.  Most epithelial cells are innervated.

3. Cellular Attachments Three major types of cellular junctions 1. Tight junctions 2. Desmosomes 3. Gap junctions

Tight Junctions  Formed by the fusion of the outermost layers of the plasma membranes of adjoining cells  Found in tissues in which there can be no leaks (urinary bladder, digestive tract)

Desmosomes  Mechanical coupling formed by filaments that interlock with one another (kind of like velcro)  Tonofilaments extend from the plaque into the cytoplasm.  Found in tissues that undergo repeated episodes of tension and stretching (skin, heart, uterus)  Hemidesmosomes link epithelial cells to the basement membrane.

Gap Junctions  Tubular channel proteins (called connexons) that extend from the cytoplasm of one cell to the cytoplasm of another  Allow exchange and passage of ions and nutrients  Found in intestinal epithelial cells, the heart, and smooth muscle tissue

4. Basement Membrane  Meshwork of fibers that cements the epithelial cell to the underlying connective tissue  Also called basal lamina  Varies in thickness  Acts as a partial barrier between the epithelial cell and the underlying connective tissue

5. Surface Specialization Surfaces of epithelial cells vary depending on where they are located and what role they play in the function of the tissue –Smooth (Blood vessels) –Microvilli (called the brush border)-increases surface area for absorption –Cilia –Keratin (water proof).

Classification of Epithelial Tissue 6. Shapes and 7. Layers Shape of the cells: Squamous, cuboidal, and columnar Number of layers of cells: Simple or stratified

Simple Squamous Epithelium Fragile and thin Found lining surfaces involved in the passage of either gas or liquid Flat and smooth

Simple squamous epithelial cells are found in: –Walls of alveoli of lungs –Walls of blood vessels –Inner heart chamber (endothelium)

Squamous cells

Squamous Cells

Simple Cuboidal Epithelium Single layer of cube- shaped cells Round, dark-staining nuclei aligned in a single row Occurs in areas of the body where secretion and absorption take place

Simple cuboidal epithelial cells are found in: –Kidney Tubules –Salivary Glands

Simple cuboidal

Simple Cuboidal

Simple Columnar Epithelium Elongated and closely packed together Nuclei aligned in a row at the base of the cell near the basement membrane Found in many excretory ducts as well as in the digestive tract

Simple columnar epithelial cells are found in: –Inside small intestine (secretes protective mucous)

Simple Columnar

Stratified Squamous Epithelium Multilayered Occur in areas of the body subject to mechanical and chemical stresses Protect underlying tissues

Stratified squamous epithelial cells are found in: –Surface of the skin –Lines the mouth –Anywhere that provides protection

Stratified Squamous

Stratified Cuboidal Epithelium Usually two layers of cuboidal cells Found primarily along large excretory ducts Protects underlying tissues

Stratified cuboidal epithelial cells are found in: –Sweat glands –Mammary glands –(lines the ducts)

Stratified Columnar Epithelium Found only in select parts of the respiratory, digestive, reproductive systems and along some excretory ducts Function in secretion and protection

Stratified columnar epithelial cells are found in –Lower epiglottis –Pharynx –Rare

Pseudostratified Columnar Epithelium Cell nuclei are found at different levels across the length of the tissue Some cells do not reach the luminal surface Found in respiratory tract and in portions of the male reproductive tract

Pseudo columnar epithelial cells are found in: –Respiratory Tract (w/ cilia on apical surface) –Lining the trachea –Lining the nasal cavity

Transitional Epithelium Stratified epithelium with a basal layer of cuboidal or columnar cells and a superficial layer of cuboidal or squamous cells Found in areas of the body required to expand and contract as part of their normal function Urinary bladder

Transitional epithelium- bladder

Vocabulary list due Wednesday Reading Assignment Questions from Textbook Friday: Vocab Quiz Quiz on Epithelium Identification (what does it look like) Begin Glandular epithelium…

Quiz on Epithelium and glands on Thursday (identification) Worksheet from Textbook due Thursday Vocab quiz on Friday Wed, Aug 13…

Definition: both words describe movement of “substances” –Excretions - removes substances from the body Tears, feces, sweat, urine, CO2 “waste” products –Secretions - move “substances” within the body, from one point to another Enzymes, hormones, saliva Secretions and Excretions

Glandular Epithelium Groups of cells that manufacture and discharge a secretion Classification of glands 1.Presence or absence of ducts 2.Number of cells that compose them 3.Shape of the secreting ducts 4.Complexity of the glandular structure 5.Type of secretion they produce 6.Manner in which the secretion is stored and discharged

Endocrine Glands Glands that do not have ducts or tubules / secretions are distributed throughout the body Produce and secrete hormones into the bloodstream or the lymphatic system Part of a complex, biochemical network known as the endocrine system which includes pituitary gland, adrenal gland, parathyroid gland, pancreas, thyroid gland, testes, ovaries,

Pituitary gland The endocrine glands are made up of simple epithelial cells…

Exocrine Glands Discharge secretions via ducts directly into local areas (except for goblet cell-no duct and endocrine glands which have no ducts) Unicellular (goblet cell) or multicellular

Goblet Cell Single cell exocrine gland Ductless and composed of modified columnar epithelial cell Found among columnar cells of the respiratory and digestive tracts and the conjunctiva of the eye Secretes mucin Provides lubrication and “entrapment”

Multicellular Exocrine Glands Composed of a secretory unit and a duct Secretory unit is usually surrounded by connective tissue rich in blood vessels and nerve fibers

Classification of Exocrine Glands Ducts: –Simple: main duct is unbranched –Compound: main duct is branched Shape of secretory portions –Tubular: secretory cells form a long channel of even width –Alveolar or acinar: secretory unit forms a rounded sac –Tubuloalveolar, or tubuloacinar: secretory units possess both tubular and alveolar qualities

Simple coiled tubular (not pictured)

SimpleTubular Stomach, intestine Simple branched tubular Stomach, mouth, tongue, esophagus Branched alveolar or acinar Sebaceous glands Compound alveolar Mammary glands, kidney tubules, mucous glands- mouth Mammary glands Compound tubular Simple Coiled Sweat glands Simple alveolar Sebaceous glands

Classification of Exocrine Glands Merocrine glands package their secretions and release them via exocytosis as they are manufactured. Apocrine glands store their secretions and then release the top part of the cell into the duct system Holocrine glands store their secretions and then release the entire contents of the cell

Classification of Exocrine Glands Type of secretion produced Serous secretions –Watery –Contain a high concentration of enzymes Mucous secretions –Thick, viscous –Composed of glycoproteins. –Protects apical layer (intestines), traps microorganism so cilia can move them out (respiratory) Mixed exocrine glands contain both mucous and serous components (digestive and respiratory.