Tissues Organized groups of cells that are similar in structure and function.
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Transcript of Tissues Organized groups of cells that are similar in structure and function.
Tissues
Organized groups of cells that are similar in structure and function
Tissues
• Tissues are organized into organs.• Organs can contain more than one type• Four main types:– Epithelial Tissue– Connective Tissue– Muscle Tissue– Nervous Tissue
Epithelial Tissue• Also called epithelium
(epithe = covering)• Lining, covering, and
glandular tissue of body• Functions include
protection, absorption, filtration, and secretion
• Special Properties:– Avascular– Reproduce rapidly – Packed together tightly
Epithelial Tissues
• Each epithelium has two names:– One signifies the number of cell layers : • simple epithelium (one layer of cells) • stratified epithelium (more than one layer)
– The second name describes the shape of its cells• Squamous cells (flattened like fish scales) • Cuboidal cells (cube-shaped like dice)• Columnar cells (shaped like columns)
Simple squamous epithelium
• Single layer• Thin squamous
cells resting on basement membrane
• Forms serous membranes that line the body cavity
• In air sacs of lungs
Simple cuboidal epithelium
• Single layer• Cuboidal cells
resting on basement membrane
• Common in glands and ducts
• Forms walls of kidney tubules
Simple columnar epithelium
• Single layer• Columnar cells• Goblet cells that
secrete mucus are in this layer
• Lines digestive tract
• Mucous membranes that line body cavities
Pseudostratified Columnar Epithelium
• Vary in height so false impression that stratified
• Functions in secretion and absorption
• Lines respiratory tract
Stratified squamous epithelium
• Most common stratified epithelium
• Found in areas that receive friction, like esophagus, mouth, and skin
Transitional Epithelium• Highly modified
stratified squamous epithelium
• Forms lining of urinary bladder, ureter, and urethra
• Basal layer = columnar / cuboidal
• When organ is distended (stretched) with urine, the cells flatten and become squamous-like
• Allows ureter wall to stretch with greater volumes of urine
Glandular Epithelium• Gland – one or more cells that make and
secrete a product• Secretion – product of gland that contains
proteins in aqueous solution• Endocrine gland – ductless, diffuse secretion
(hormones) directly into the blood (ex: thyroid, adrenal, pituitary glands)
• Exocrine gland – retain ducts, secretions empty through ducts to epithelial surface (ex: sweat glands, liver, pancreas)
Connective Tissue
• Connects body parts• Most abundant and widely distributed tissue• Functions include protecting, supporting, and
binding together other tissues• Well vascularized (exceptions tendons,
ligaments; cartilage is avascular)• Connective tissues includes cells plus
extracellular matrix – nonliving substance outside cells
Extracellular Matrix• Produced by connective tissue and
secreted to exterior• Ground substance composed largely
of water and proteins• Cell adhesion proteins allow
connective tissue cells to attach to matrix fibers
• The following types of connective tissue are discussed in order of most rigid to softest
Bone
• Bone – osseus tissue, composed of bone cells in cavities called lacunae, surrounded by hard matrix of calcium salts and collagen fibers
• Protects and supports body organs
Cartilage
• Less hard and more flexible than bone• Chondrocyte – mature cartilage cell• Hyaline cartilage – most widespread– Abundant collagen fibers in a matrix with glassy
appearance (hyalin = glass)– Forms larynx, connects ribs to sternum, covers
bones to form joints– Fetus skeleton made of hyaline cartilage
Hyaline Cartilage
Fibrocartilage
• Highly compressible
• Forms disks between vertebrae
Elastic Cartilage
• Found in a structure with elasticity
• Supports external ear
Dense Connective Tissue
• Also called dense fibrous tissue• Collagen fibers as main matrix element• Fibroblasts – fiber forming cells between
collagen fibers• Two types:– Tendons – connect skeletal muscles to bones– Ligaments – connect bones to bones at joints
• Ligaments more stretchy (more elastic fibers) than tendons
Dense Fibrous Tissue
Loose Connective Tissue
• Softer, fewer fibers and more cells than other connective tissues except blood
• Areolar tissue – most widely distributed connective tissue– Soft, pliable, “cobweb”-like tissue– Cushions and protects body organs it wraps– Provides reservoir of water and salts for
surrounding tissue– site where nutrients are obtained and wastes
released
Areolar Tissue
Loose Connective Tissue• Adipose Tissue – commonly called fat– Areolar tissue in which fat cells predominate– Insulates body and protects it from extreme T– Stored in body and cushions some organs
Adipose Tissue
• Oil occupies most of a fat cell’s volume and compresses the nucleus, displacing it to one side
Blood
• Blood – vascular tissue; consists of blood cells surrounded by a matrix called blood plasma
• Atypical connective tissue• Transport vehicle for cardiovascular system
Muscle Tissue
• Muscle tissues are highly specialized to contract or shorten to produce movement
Skeletal Muscle
• Skeletal muscle tissue – skeletal muscle organs connected to the skeleton.
• Controlled voluntarily• Form flesh of the body – muscular system• Contraction leads to pulling on bone or skin• Result is movement or changes in expression• Cells are long, cylindrical, multinucleate, and
have obvious striations
Skeletal Muscle
• Long• Cylindrical• Multinucleate• Striations• Called “muscle
fibers”
Cardiac Muscle
• Found only in the heart• Contractions lead to propelling of blood
through the blood vessels• Cardiac muscle cells are uninucleate, short,
branching with striations and fit tightly together at intercalated disks– Gap junctions with ion flow
• Involuntarily controlled
Cardiac Muscle
• Cells short• Striated• Branching• Uninucleate• Intercalated
Discs
Smooth Muscle
• Smooth muscle (Visceral Muscle) – found in walls of hollow organs (stomach, uterus, blood vessels, etc.)
• Contractions lead to the organ constricting or dilating so substances are propelled
• No striations, uninucleate, spindle-shaped
Smooth Muscle
• No striations• Uninucleate• Pointed ends
(spindle shaped)
Nervous Tissue
• Nervous Tissue – made of cells called neurons• Neurons receive and conduct electrochemical
impulses from one part of body to another• Neurons and supporting cells (insulate and
protect neurons) make up the nervous system: the brain, spinal chord, and nerves
• Cytoplasm drawn out in extensions allows neurons to conduct impulses long distances
Neuron
• Neurons in human hippocampus