Chapter 5 Tissues

Introduction Cells are specialized for particular functions CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. Introduction Cells are specialized for particular functions Where have we heard this before?? Form Follows Function!! (See? What we learned before IS important!) Tissues – group of cells with similar structure and function Histology – study of tissue

Tissue Four major types Epithelial – protection/secretion/absorption Connective – support and structure Muscle – movement (internal and external) Nervous – communication and control

Epithelial Tissue General characteristics: Anchored to connective tissue underneath by a basement membrane Avascular – no blood vessels within it Nutrients and wastes are exchanged with the blood stream via diffusion Divide easily and often! Continually replacing damaged cells Tightly packed Creates barriers

Free Surface vs. Basement Membrane

Classification Combination of two things: Shape of cells Number of cell layers

Classification Shape Squamous - flattened Cuboidal - cube-shaped Columnar - column-like

Classification Number of cell layers Simple Stratified One layer Found in areas of transport Stratified More than one layer Found in areas of high abrasion

Simple Squamous Epithelium Made of a single layer of thin/flattened cells Nuclei are broad and thin Functions: diffusion, filtration, osmosis, and covering surfaces Locations: air sacs, capillary walls, blood vessels, body cavities Broad and thin nuclie Easily damaged

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Simple Cuboidal Epithelium Made of a single layer of cube-shaped cells Nuclei are spherical and found in the middle of the cell Functions: secretion (from glands) and absorption Locations: covering the ovaries, lining kidney tubules, lining of glands

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Simple Columnar Epithelium Made of a single layer of “tall” cells Nuclei are often at the bottom of the cell near the basement membrane Cell may be ciliated Functions: protects underlying tissues, secretes digestive fluids, and absorbs nutrients Locations: lines the uterus, stomach, and intestines

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Pseudostratified Columnar Epithelium Appear layered… but are not. (“Pseudo” = Fake/False) All cells touch the basement membrane Made of a single layer of “tall” cells Nuclei are found at different levels Functions: line and sweep debris from the respiratory tubes Locations: passageways of the respiratory system

Stratified Squamous Epithelium Made of layers of flattened cells Thick! Functions: protect tissue underneath Locations: outer layer of skin, lines the mouth, throat, vagina, and anal canal Cell division happens deep – more superficial cells are squished as more cells are created underneath “Squamous” label is based on surface cell appearance

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Stratified Cuboidal Epithelium Made of 2-3 layers of cuboidal cells Provides greater protections than just one layer Functions – protection, secretion, absorption Locations – lines larger ducts of the mammary glands, sweat glands, salivary glands, and pancreas

Stratified Columnar Epithelium Made of several layer of “tall” cells Functions: protection and secretion Locations: male urethra and parts of the pharynx

Connective Tissue General Characteristics Bind, support, protect, fill spaces, store fat, produce blood cells, protect against infection, and repair tissue damage Have an abundant extracellular matrix Have a good blood supply (except cartilage) Can be very rigid or very flexible

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Loose Connective Tissue Made of mainly fibroblasts, a gel matrix, collagenous, and elastic fibers Functions – attaches skin to deep organs, fills spaces between muscles, under most epithelial layers (blood vessels nourish epithelial cells) Location – beneath skin and epithelial tissue, between muscles and organs

Adipose Tissue Made of adipocytes Adipo – fat Cytes - cells Functions – store fat (energy), insulation, cushion joints and organs Locations – beneath the skin, around the kidney, surface of the heart, behind the eyeballs

Bone Made of mineral salt, collagen fibers, and osteocytes (bone cells) Function – internal support, protection, attachment site for muscles, location of blood cell formation Location – Entire skeletal system

Blood Made of red and white blood cells (RBCs and WBCs) in a liquid matrix called plasma Function – maintain a stable environment (homeostasis!), transport substances throughout the body Location – blood vessels and heart

Dense Connective Tissue Made of densely packed collagen fibers Very strong but not a good blood supply Can withstand pulling Slow to heal Function – binds organs (bone and muscle) Location – tendons and ligaments

Cartilage Rigid connective tissue that provides a supportive framework for various structures Lacks a blood supply Slow to heal

Hyaline Cartilage Most common Made of fine collagen fibers, white Function – support, protect, provide framework Location – nose, end of bones in joints Between ages 30-70, a nose may lengthen and widen by as much as half an inch, and the ears may lengthen by a quarter of a ince due to the fact that cartilage is one of the few tissues that continues to grow as we age.

Elastic Cartilage Made of dense network of elastic fibers More flexible Functions – supports, protects, provides flexible framework Location – framework for external ear, parts of the larynx

Fibrocartilage Made of many collagenous fibers Function – support, shock absorption Location – intervertebral disks, knees, pelvic girdle

Muscle Tissue General Characteristics Composed of elongated cells (fibers) that can contract

Skeletal Muscle Made of skeletal muscle cells (muscle fibers) that are long, cylindrical, have many nuclei, and have striations (alternating light and dark fibers) Functions – voluntary movement of skeletal parts Locations – Any muscle that is attached to a bone

Smooth Muscle Lacks striations, only has one nucleus, and contracts involuntarily Functions - Involuntary movements of internal organs Locations – walls of internal organs, digestive tract, blood vessels, and bladder

Cardiac Muscle Is striated, has one nucleus, cells are connected by intercalated disks Functions – Involuntary heart movements Location - heart

Nervous Tissue General Characteristics: sense certain types of changes in surroundings and respond by transmitting nerve impulses to other nerve cells, muscle, or glands

Nervous Tissue Made of neurons (nerve cells) and neuroglial cells (supporting cells) Function – sensory reception, conduction of nerve impulses Location – brain, spinal cord, nerves