1

Lecture 3

Histology

Study of Tissues

Introduction

  • A tissues is a mass of similar cells and cell products that forms a discrete ______of an organ and performs a specific function
  • A matrix is material that surrounds the cells, and is composed of fibrous proteins and ground substance
  • Tissue differences:
  • Types and ______of the cells
  • Characteristic of the matrix (extracellular material) that surrounds the cells
  • Relative amount of space occupied by cells versus ______

Primary Tissue Classes

  • Epithelial Tissue
  • Epithelium is a type of tissue composed of one or more layers of closely adhering cells, either covering an organ surface or forming the secretory tissue and ducts of a ______
  • It’s found in the linings of organs, the lining of body cavities, and forms the ______of the skin
  • The extracellular material is so thin that there is no room for blood vessels, so they rely on blood vessels in loose connective tissue for nourishment
  • Anchoring the epithelium to the connective tissue below is a layer of tissue called the ______membrane
  • Surfaces of epithelium that face the basement membrane are basal surfaces
  • Surfaces that face away from the basement membrane are ______surfaces
  • Types of Epithelium:
  • Simple – having only a ______layer of cells
  • Simple squamous – single layer of flat, scale-like cells
  • Found in air sacs of lungs, glomerular capsules of kidneys
  • Allows rapid ______or transport through membranes
  • Simple cuboidal – single layer of cube-shaped (though perhaps rounded) cells
  • Found in the liver, thyroid, many glands
  • For absorption and ______
  • Simple columnar – single layer of cells that are taller than they are wide – greater volume allows more absorption & secretion
  • Found in lining of stomach, intestines, uterus
  • Absorption, secretion of ______
  • Simple ______columnar epithelium has cilia to move the egg through the uterine tubes
  • Pseudostratified columnar – Epithelium that has the appearance of having multiple layers (stratified), but which actually has a single layer of cells that are not all the same height
  • Found in ______tract
  • Secretes and propels mucus
  • This tissue has cilia to move mucus and dust
  • Stratified – having ______or more layers of cells, with some cells resting on others, rather than being in direct contact with the basement membrane
  • Stratified squamous – multiple layers of flat, scale-like cells
  • Actually, not all of the cells in this tissue will necessarily appear flattened. The tissue type is named for the flattened cells that appear at the ______
  • There are two kinds of stratified squamous epithelium, one containing the protein keratin, and the other without
  • Keratinized stratified squamous epithelium is found on the skin surface and resists water loss and provides resistance to ______penetration
  • Found in the epidermis
  • Resists abrasion, penetration, water loss
  • Nonkeratinized stratified squamous epithelium provides a surface that is abrasion resistant, but also moist and slippery
  • Found in the ______, esophagus, vagina
  • Resists abrasion and penetration by pathogens
  • Stratified cuboidal – multiple layers of cube-shaped cells
  • Found in sweat gland ducts, in ovaries and testes
  • Contributes to sweat, secretes hormones, produces sperm
  • Stratified columnar – multiple layers of cells that are taller than they are wide
  • Rare, found only in parts of the pharynx, anal canal, ______
  • Transitional epithelium – multiple layers of cells that were once thought to represent a transitional stage between squamous and columnar
  • Found in the urinary bladder and part of the urethra
  • Stretches to allow ______of urinary tract
  • Connective Tissue
  • Functions:
  • ______of organs – tendons bind muscle to bone, ligaments bind bone to bone, fat holds the kidneys in place, etc.
  • Also support, protection, movement, storage, heat production, transport
  • Components:
  • Cells
  • Fibroblasts – Large flat cells that appear tapered at the ends and produce the fibers and ground substance that form the ______of the tissue
  • Macrophages – Large phagocytic cells that engulf and destroy bacteria, foreign matter, or dead and dying cells
  • ______– White blood cells that react against bacteria, toxins, and other foreign agents
  • Mast cells – Cells found along blood vessels that secrete heparin or histamine to inhibit blood clotting or increase blood flow
  • Adipocytes – Fat cells
  • Fibers
  • Collagenous fibers – Tough, flexible fibers, made of collagen
  • Reticular fibers – Thin collagen fibers coated with glycoprotein, forming a spongelike network
  • Elastic fibers – Fibers composed of a protein called ______, which has a coiled structure that allows it to stretch and recoil like a rubber band
  • Ground substance – Three classes of large molecules that form a gel in connective tissue that slowes down the spread of bacteria and other pathogens. They also bind tissue components together.
  • Fibrous connective tissue
  • Loose connective tissue – Much space is occupied by ground substance
  • Areolar tissue – has fibers that run in random directions and has highly variable appearance
  • It ______blood vessels and nerves, allowing passage through other tissues
  • Provides space for immune defense, and provides nutrients and waste removal for overlying epithelia
  • Reticular tissue – has a mesh-like appearance and forms the structural framework of the lymph nodes, spleen, thymus, and bone marrow
  • Adipose tissue – tissue in which adipocytes are the dominant cell type
  • It stores energy and provides cushioning
  • Dense connective tissue – ______take up more space than cells or ground substance
  • Dense regular connective tissue
  • Has fibers that are closely packed and the fibers run ______to the direction of force (such as in ligaments and tendons)
  • Binds muscle to bone and bone to bone
  • Dense irregular connective tissue
  • Has thick bundles of collagen which run in ______directions
  • It binds skin to muscle and withstands stress in unpredictable directions
  • Cartilage – supportive connective tissue with a flexible rubbery matrix
  • Hyaline Cartilage – Found in the trachea and over the ends of ______at movable joints
  • It holds the airway open and eases joint movement
  • Elastic Cartilage – Fount in the external ear and nose
  • It provides flexible, elastic support
  • Fibrocartilage – Fount in the pubic symphysis and between the bones of the ______column
  • It withstands compression and absorbs shock
  • Bone
  • Spongy bone is bone tissue that fills the heads of the long bones.
  • It is made up of many long delicate slivers that give it a ______appearance
  • Compact bone is bone tissue that forms the surface of skeleton.
  • It is more dense calcified tissue, with no spaces visible to the naked eye
  • Blood
  • Plasma is the ground substance part of the blood (the liquid part)
  • Formed elements are cells and cell fragments that carry oxygen, fight infection, or help to form ______if an injury occurs
  • Nervous and Muscular Tissue
  • Nervous Tissue is tissue specialized for rapid communication by means of electrical and chemical signals
  • Neurons are specialized cells that detect stimuli and transmit information ______to other cells
  • Soma – cell body that houses the nucleus and other organelles
  • Dendrites – processes extending from the cell body that ______signals from other cells
  • Axons – processes (1 for each neuron) that send outgoing signals from the soma
  • Glial cells – cells that support and assist the neurons
  • Muscular Tissue is tissue that is specialized to contract when stimulated (thus exerting physical force on other tissues)
  • Skeletal muscle –
  • Long cylindrical cells, with visible ______and multiple nuclei per cell
  • Muscles attached to bones, but also muscles controlling voluntary sphincters
  • Used for body movements, breathing, speech, and other voluntary control
  • Cardiac muscle
  • Short branched cells connected by ______discs and having only one nucleus per cell
  • Found in the heart
  • Used for pumping blood (involuntary)
  • Smooth muscle
  • Short fusiform (spindle-shaped) cells, each with one nucleus and no striations
  • Found as sheets of tissue in the walls of internal organs, or as part of sphincters of the urethra and anus
  • Used for movement of ______through the GI tract or urine through the urinary system, etc. that are involuntarily controlled
  • Glands and Membranes
  • Glands are organs or cells that secrete substances for use in the body or for elimination from the body
  • Cells vs organs
  • Single-celled glands – ______cells are shaped somewhat like a wineglass, and are found in the epithelia of many mucous membranes
  • Multicellular glands – include all other glands in which multiple cells work together to produce secretions
  • Exocrine glands are glands that convey their secretions through ______to the surface of the body or to the lumen (cavity) of another organ
  • Endocrine glands secrete their products directly into the bloodstream for transport to ______cells
  • Types of secretions
  • Serous glands produce relatively thin, watery fluids, such as perspiration, milk, or tears
  • Mucous glands produce a glycoprotein called ______, which absorbs water to form mucus (note the different spelling)
  • Mixed glands contain both serous and mucous cells and produce a mixture of the two types of secretions
  • Cytogenic glands release whole cells (sperm or egg cells)
  • Methods of secretion
  • Merocrine glands release their secretions by exocytosis (only the secretion is released from the gland)
  • ______glands accumulate products within the cell and then the entire cell disintegrates, so that the substance released is a mixture of product and cell fragments
  • Apocrine glands were named when it was believed that bits of apical cytoplasm broke away from the cell surface. Technically this isn’t true, but there are differences between these glands and merocrine glands.
  • Membranes
  • Cutaneous membranes – ______
  • Stratified squamous epithelium resting on a layer of connective tissue
  • Mucous membranes – membranes that line passageways leading to the exterior
  • Digestive, respiratory, and reproductive tracts
  • Serous membranes – membranes that produce watery serous fluid
  • Line the insides of some body cavities and form a smooth surface on the outer surface of some viscera
  • Endothelium – Simple squamous epithelium that lines the lumens of the blood vessels, heart, and lymphatic vessels
  • Synovial membranes – Membranes made of connective tissue that span the gap from bone to bone and secrete slippery ______fluid into the joint
  • Tissue Growth and Repair
  • Growth
  • Hyperplasia – growth through cell multiplication
  • ______- enlargement of existing cells
  • Repair
  • Regeneration - Replacement of cells by the same type of cells
  • Fibrosis – Replacement of damaged tissue with ______tissue, composed mainly of collagen