Chapters 3 and 5Cells and Tissues

Objectives: You will be able to1. classify major types of cells, including

squamous, cuboidal, columnar, simple, and stratified (ACOS 3).

2. classify tissues as connective, muscular, nervous, or epithelial (ACOS 4).

Three Basic Cell PartsA. cell membrane: (also called plasma

membrane) fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment

B. nucleus: control center; contains genes

C. cytoplasm: cellular material outside the nucleus and inside the cell membrane; fills out the cell

Cell NucleusD. nuclear membrane (envelope): double

membrane barrier that binds the nucleusE. nucleoplasm: jellylike fluid enclosed in the

nuclear membrane; nucleoli and chromatin are suspended in the nuclear membrane

F. nucleoli: small, dark-staining, round bodies where ribosomes are assembled

G. chromatin: loose network of bumpy DNA threads and proteins (becomes individual chromosomes when dividing) that is scattered throughout the nucleus

OrganellesH. rough endoplasmic reticulum: system of fluid-

filled cisterns that coil and twist through the cytoplasm and is studded with ribosomes; cell’s “membrane factory”

I. smooth endoplasmic reticulum: continuation of rough variety but with no protein synthesis; functions in cholesterol synthesis and breakdown, fat metabolism and detoxification

J. ribosomes: tiny, round, dark bodies made of proteins and ribosomal RNA; actual site of protein synthesis; some float free, some are attached

Organelles-cont.K. Golgi apparatus: appears as a stack of

flattened membranous sacs, associated with swarms of tiny vesicles; principle “traffic directors” for cellular proteins; function is to modify and package proteins

L. mitochondria: sausage shaped organelles; enzymes carry out reactions in which oxygen is used to break down foods and release energy; metabolically “busy” cells (liver and muscle) have hundreds of them, while cells that are relatively inactive (unfertilized egg) have just a few

Organelles-cont.M. lysosomes: (breakdown bodies) membrane

bags containing powerful digestive enzymes; function as the cell’s demolition sites; especially abundant in white blood cells

N. peroxisomes: membranous sacs containing powerful oxidase enzymes that use molecular oxygen (O2) to detoxify a number of harmful substances

Organelles-cont.O. microfilaments and microtubules: two

types of thin, threadlike strands within the cytoplasm

P. centrosome: structure near the Golgi apparatus and nucleus; consists of two hollow cylinders called centrioles; distribute chromosomes to newly forming cells during mitosis

Organelles…cont.

Q. cilia and flagella: motile extensions from the surfaces of certain cells; flagella are significantly longer than cilia

R. vesicles: membranous sacs formed by part of the cell membrane folding inward and pinching off

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B

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Body Tissues

• tissues—groups of cells that are similar in structure and function

• Four primary tissue types1. epithelial tissue (covering)2. connective tissue (support)3. muscle tissue (movement)4. nervous tissue (control)

• In addition to cells, all tissues include a non-living portion called the extracellular matrix.

Table 5.1 page 92

Epithelial Tissue

• also called epithelium

• covers organs, forms the inner lining of body cavities and lines hollow organs

• nearly all substances given off or received by the body pass through epithelium

• functions include protection, absorption, filtration, and secretion

Special Characteristics of Epithelium

• cells fit closely together to form continuous sheets

• lack blood vessels• readily divide• Membranes always have one free surface or

edge (called apical surface). • The lower surface rests on a basement

membrane, a thin, non-living material secreted by the cells.

Classification of Epithelium• Epithelial tissues are classified according to shape

and number of layers of cells. Each epithelium is given two names—the 1st to indicate the relative number of cell layers it has and the 2nd to indicate the shape of the cells.

– 1st name determination: number of cell layers

• simple: one layer of cells

• stratified: more than one layer

of cells

Classification of Epithelium—cont.– 2nd name determination: shape of cells

• squamous: flattened like fish scales

• cuboidal: cube-shaped like dice

• columnar: tall, elongated cells

Simple Squamous Epithelium• single layer of thin, flattened cells resting

on a basement membrane

• substances pass rather easily so it is common in membranes where filtration or exchange of substances by rapid diffusion occurs

Simple Squamous Epithelium…cont

• found in the air sacs of the lungs, walls of the capillaries, and forms the serous membranes– serous membranes (serosae)—slick

membranes that line the anterior body cavity and cover the organs in that cavity

• easily damaged

• broad and thin nuclei

Simple Squamous Epithelium

Simple Cuboidal Epithelium• one layer of cube-shaped cells

resting on a basement membrane

• centrally located, spherical nuclei

• common in glands and the ducts

Simple Cuboidal Epithelium…cont• forms the walls of the kidney tubules and

covers the surface of the ovaries

• in kidneys, functions in secretion and absorption; in glands, secretes glandular products

Simple Cuboidal Epithelium

Simple Columnar Epithelium• made up of a single layer of tall cells that

fit closely together

• protects underlying tissue because it is thick

• nuclei are usually located at about the same level, near the basement membrane

Simple Columnar Epithelium…cont• can be ciliated or nonciliated

• ciliated simple columnar line the female reproductive tubes

• nonciliated simple columnar lines the uterus and the entire length of the digestive tract

Simple Columnar Epithelium—cont.• often have many minute, cylindrical processes

extending from the surface call microvilli• goblet cells—specialized flask-shaped glandular

cells that produce a lubricating mucus, often seen among simple columnar

• mucous membranes (mucosae)—epithelial membranes that line the body cavities open to the body exterior

Simple Columnar Epithelium

Pseudostratified Columnar Epithelium

• appear stratified or layered, but are not

• rests on a basement membrane with some cells being shorter than others and nuclei appearing at different heights above the basement membrane

Pseudostratified Columnar Epithelium…cont

• commonly have cilia and goblet cells

• line the passages of the respiratory system

Pseudostratified Columnar Epithelium

Stratified Epithelium

• consist of two or more cell layers

• considerably more durable than simple epithelium

• function is primarily to protect

• includes stratified squamous, stratified cuboidal, stratified columnar, transitional and glandular

• named for the cells at the free surface

Stratified Squamous Epithelium

• most common stratified epithelium in the body

• cells at the free edge are squamous cells, those close to the basement membrane are cuboidal or columnar

Stratified Squamous Epithelium…cont

• found in sites that receive a lot of friction or abuse, such as the esophagus, mouth and outer portion of the skin (epidermis)

Stratified Cuboidal Epithelium

•usually has just two cell layers

•fairly rare in the body

• found mainly in the ducts of large glands

Stratified Columnar Epithelium

• surface cells are columnar

• fairly rare in the body

• found mainly in the ducts of large glands

Transitional Epithelium• forms the lining of only a few organs—the

urinary bladder, the ureters, and part of the urethra

• specialized to change in response to increased tension

• also forms a barrier that helps prevent the contents of the urinary tract from diffusing back into the internal environment

Transitional Epithelium

Glandular Epithelium• composed of cells that are specialized to

produce and secrete substances into ducts or into body fluids

• gland—consists of one or more cells that make and secrete a particular product

• secretion—product of a gland that typically contains protein molecules in an aqueous fluid

• Two major types of glands develop from epithelial sheets: endocrine and exocrine.

1. Endocrine Glands

• glands that secrete their products into tissue fluid or blood

• often called ductless glands because they lose their connection to the surface (duct)

• secretions (all hormones) diffuse directly into the blood vessels that weave through the glands

• examples: thyroid, adrenals, pituitary

Endocrine Glands

2. Exocrine Glands

• glands that secrete their products into ducts that open onto surfaces

• retain their ducts

• include sweat and oil glands, liver and pancreas

• Types of Exocrine Glandular Secretions Table 5.2 on page 98

A. Merocrine Gland

• Glands that release watery, protein-rich fluids by exocytosis

• Salivary glands,

pancreatic glands,

sweat glands

B. Apocrine Glands

• Glands that lose small portions of their glandular cell bodies during secretion

• Mammary glands

C. Holocrine Gland

• Glands in which the entire cell lyses during secretions

• Sebaceous glands of

the skin

Types of Exocrine Glands