4 Basic Tissues Epithelial Tissue covers exposed surfaces

4 Basic Tissues • Epithelial Tissue – covers exposed surfaces ( skin ) – lines hollow organs, internal passageways and ducts ( digestive tract, urinary tract, reproductive) – forms glands • Connective Tissue – material found between cells – supports and binds structures together – stores energy as fat – provides immunity to disease

4 Basic Tissues (contd. ) • Muscle Tissue – cells shorten in length producing movement Two types: Voluntary – skeletal Involuntary – Cardiac and smooth • Nerve Tissue – cells that conduct electrical signals – detects changes inside and outside the body

Epithelial Tissue -- General Features • Cellularity – composed almost entirely of cells • Special contacts – form continuous sheets held together by tight junctions and desmosomes • Polarity – apical and basal surfaces • Basement membrane– supported by connective tissue; reticular and basal laminae • Avascular – contains no blood vessels but supplied by nerve fibers • Regeneration – rapidly replaces lost cells by cell division

Functions • Physical protection – protects exposed and internal surfaces from abrasions, dehydration, and destruction from chemical agents. • Absorption – The lining of the gut and respiratory tract allow for nutrients to be absorbed from the gut and the exchange of gases between air in lungs and blood. • Excretion- The unique lining of the kidney tubules makes the excretion and concentration of excretory products in the urine possible. • Produces secretions – Glandular epithelial is adapted for secretory activity (hormones, mucus, digestive juices, and sweat). • Provides sensation – good nerve supply- sensory nerves of eyes, ears, nose, skin. • Specialized Epithelium – a) Microvilli – absorption/secretion – found in digestive and urinary tracts b) Cilia – Respiratory tracts, the synchronized beating moves mucous up from lungs to throat.

Types of Epithelium • Covering and lining epithelium – epidermis of skin – lining of blood vessels and ducts – lining respiratory, reproductive, urinary & GI tract • Glandular epithelium – secreting portion of glands – thyroid, adrenal, and sweat glands

Classification of Epithelium • Classified by arrangement of cells: – simple = one cell layer thick. – stratified = more than one layer thick. Located where protection from mechanical or chemical stresses are needed. ( skin , mouth ) *pseudostratified = single layer of cells where all cells don’t reach apical surface • nuclei at found at different levels so it looks multilayered • Classified by shape of surface cells – squamous =flat – cuboidal = cube-shaped – columnar = tall column **transitional = shape varies with tissue stretching

Location of Epithelium • Simple Squamous Epithelium: lining ventral body cavities; lining heart and blood vessels; alveoli of lungs; inner lining of cornea. • Simple Cuboidal Epithelium: Glands, ducts, portion of kidney tubules • Simple Columnar Epithelium: Lining of stomach, intestine, gall bladder, uterine tubes. • Stratified Squamous Epithelium: Surface of skin; lining of mouth, throat, esophagus, rectum, anus and vagina. • Stratified Cuboidal Epithelium: (rare) Linings of sweat gland ducts and male urethra. • Stratified Columnar Epithelium: small areas of pharynx, epiglottis, mammary glands, salivary glands ducts and urethra • Pseudostratified Ciliated Columnar Epithelium: Lining of nasal cavity, trachea (windpipe), bronchi, portion of the male reproductive tract. • Transitional Epithelium: Urinary bladder, ureters.

Examples of Simple Squamous • Surface view of lining of peritoneal cavity • Section of intestinal showing serosa

Example of Simple Cuboidal • Sectional view of kidney tubules

Nonciliated and ciliated Simple Columnar • Section from small intestine Section of uterine tube

Example of Stratified Squamous • Section of vagina

Stratified Cuboidal Epithelium Stratified Columnar Epithelium

Transitional Epithelium Pseudostratified Epithelium

Glandular Epithelium • Exocrine glands – cells that secrete--- sweat, tears, milk, ear wax, saliva, digestive enzymes onto free surface of epithelial layer – connected to the surface by tubes (ducts) • Endocrine glands – ductless glands (e. g. thyroid, pituitary, adrenal glands) – secrete hormones into the bloodstream

Exocrine glands, based on structure Two types: • 1) Unicellular Glands – Goblet cells • 2) Multicellular glands- consists clusters of cells Classification of multicellular glands by anatomic form: - according to the structure of the duct: a) Simple gland – have a single, unbranched duct. b) Compound glands – branched ducts. - according to the shape of the secretory portion: a) tubular – forms tubes b) Alveolar– forms blind pockets or sac c) Tubuloalveolar- both tubes and the sac

Structural Classification of Multicellular Exocrine Glands

Methods of Glandular Secretion • Merocrine -- Most glands – cells release their products by exocytosis---saliva, digestive enzymes & sweat • Apocrine – milk – upper part of cell possibly pinches off & dies – Holocrine -- oil gland – whole cells die & rupture to release their products

Exocrine glands, based on type of secretions Three types: • 1) Serous Glands – Secretes a watery solution that contains enzymes. Parotid gland. • 2) Mucous glands –secrete mucins that hydrate to form mucous. Salivary glands, submucosal glands of the small intestine. • 3) Mixed glands- submandibular

Connective Tissues • • Cells rarely touch due to extracellular matrix Matrix (fibers & ground substance secreted by cells Consistency varies from liquid, gel to solid Good nerve & blood supply except cartilage & ligaments)

Classification of Connective Tissue

Connective Tissue • Situated throughout the body but never exposed to outside environment. • Many CT are highly vascular except ligaments and cartilage. • • • FUNCTIONS 1) structural framework – bones, muscles, tendons, ligaments 2) transports fluids and dissolved materials – blood 3) protects delicate organs 4) stores energy reserves especially in the form of lipids – adipose 5) defends body from invading microorganisms – WBC’s • 3 components 1) specialized cells, 2) extracellular proteins 3) ground substance ( 2+3) = MATRIX

Connective tissue proper • Contains fibers, a viscous ground substance, and a varied cell population – Fibroblasts- abundant, hyaluronan – Mesenchymal cells-stem cells – Adipocytes-fat cells – Melanocytes-melanin – Macrophage-amoeboid cells – Mast cells-histamine – Lymphocytes-defence

Types of Connective Tissue Fibers • Collagen – tough; provides high tensile strength • Elastic – long, thin fibers that allow for stretch • Reticular – branched collagenous fibers that form delicate networks

Connective Tissue Proper: Loose • Areolar connective tissue – Gel-like matrix (loose) – – with all three connective tissue fibers Fibroblasts, macrophages, mast cells, and some white blood cells Wraps and cushions organs. Distorts easily and regains shape readily Widely distributed throughout the body It is vascular

Areolar Connective Tissue Adipose Connective Tissue

Connective Tissue Proper: Loose • Adipose connective tissue – Matrix similar to areolar connective tissue with closely packed adipocytes – The matrix is scanty and cells are closely packed – Adipose tissue is highly vascularized – Found under skin, around kidneys, within abdomen, and in breasts • White Adipose Tissue • Brown Adipose Tissue

Connective Tissue Proper: Loose • Reticular connective tissue – Loose ground substance with reticular fibers – Reticular cells lie in a fiber network – Forms a soft internal skeleton, or stroma, that supports other cell types – Found in lymph nodes, bone marrow, and the spleen

Dense Connective Tissues

Fluid Connective Tissues • Distinctive collections of cells in a fluid matrix • Blood – Formed elements and plasma • Red blood cells, white blood cells and platelets – Arteries carry blood away, veins carry to the heart – Capillaries allow diffusion into the interstitial fluid • Lymph – Interstitial fluid entering the lymphatic vessels

Blood • Connective tissue with a liquid matrix = the plasma • Cell types = red blood cells (erythrocytes), white blood cells (leukocytes) and cell fragments called platelets

Formed Elements of the Blood

Compact Bone • Osteon = lamellae (rings) of mineralized matrix – calcium & phosphate---give it its hardness – interwoven collagen fibers provide strength • Osteocytes in spaces (lacunae) in between lamellae • Canaliculi (tiny canals) connect cell to cell. They are the branching network for the exchange of materials between blood vessels and osteocytes.

Cartilage • Network of fibers in rubbery ground substance. Firm gel from polysacharide derivative called chondroitin sulfate. • Resilient and can endure more stress than loose or dense connective tissue • It’s avascular. Chondrocytes produce chemicals that discourage their growth called anti-angiogenesis factor • So all exchange of nutrients and wastes products must occur by diffusion. • Types of cartilage – hyaline cartilage – fibrocartilage – elastic cartilage

Muscle • Cells that shorten, lengthen and remain same length • Provide us with motion, posture and heat • Types of muscle – skeletal muscle-voluntary - striated – cardiac muscle-involuntary -striated – smooth muscle- involuntary

Skeletal Muscle • Cells are long cylinders with many peripheral nuclei • Visible light and dark banding (looks striated) • Voluntary or conscious control

Cardiac Muscle • Cells are branched cylinders with one central nuclei • Involuntary and striated • Attached to and communicate with each other by intercalated discs

Smooth Muscle • Spindle shaped cells with a single central nuclei • Walls of hollow organs (blood vessels, GI tract, bladder) • Involuntary and nonstriated

Nerve Tissue • • Cell types -- neurons and neuroglial (supporting) cells Nerve cell structure – nucleus & long cell processes conduct nerve signals • dendrite --- signal travels towards the cell body • axon ---- signal travels away from cell body

Membranes • Epithelial layer sitting on a thin layer of connective tissue (lamina propria) • Types of membranes – mucous membrane – serous membrane – synovial membrane – cutaneous membrane (skin)