Study of Tissues

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