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Chapter 38

BIOL 1107 Chapter Notes - Chapter 38: Tight Junction, Nervous Tissue, Muscle Tissue


Department
Biology
Course Code
BIOL 1107
Professor
Thomas Abbot
Chapter
38

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38.1 Organization of the Animal Body
βž”Aqueous solution that surrounds individual animal cells contains ions and molecules in particular
concentrations to maintain osmotic balance and maintenance needs
βž”Internal environment: fluid within organism that supplies all the needs of individual cells
β—†Allows multicellular organisms to live in various conditions
βž”Single-celled organisms exchange materials with fluid in external environment
βž”Multicellularity allows major life functions to be divided among specialized groups of cells
β—†Movement, food capture, digestion, reproduction
β—†Specialization increases efficiency
βž”Tissue: group of cells with similar structure and specialized function
β—†Epithelial, connective, muscle, nervous
βž”Organ: integrates 2+ different tissues into structure that performs a particular function
β—†Ex. eye, liver, stomach
βž”Organ system: collection of organs with related functions that interact to carry out a major body function
such as digestion
β—†Ex. nervous system is the main regulatory system of the body (brain + spinal cord + peripheral
nerves + sensory organs)
38.2 Animal Tissues
βž”Structure and integrity of tissue depend on
β—†Structure and organization of cytoskeleton within the cell
β—†Type and organization of the extracellular matrix surrounding the cell
β—†Junctions holding cells together
βž”Anchoring junctions- form button-like spots or belts that weld cells together
β—†Attach cells to each other or to ECM
β—†Most abundant in tissues subject to stretching (skin, heart muscle)
βž”Tight junctions- plasma membrane proteins of adjacent cells interact to fuse the 2 cells partly together
and create a barrier between the cells
β—†Prevent waste from leaking out of the bladder
β—†Form blood-brain barrier that blocks many potentially harmful substances in blood from reaching
the brain’s extracellular fluid
βž”Gap junctions- open direct channels between cells in the same tissue, allowing ions/molecules/electrical
signals to flow rapidly from one to another
β—†Help muscle tissue function as a unit
βž”Epithelial tissue: sheetlike layers of cells with little ECM material between them
β—†Protect internal environment and regulate the exchange of materials between internal and
external environments
β—†Some epithelia have tight junctions between cells to prevent substances from passing between
adjacent cells
●Ex. epithelial cells lining the intestine so digestion products must pass through cells to
enter the bloodstream
β—†Some epithelia have anchoring junctions to make the tissue leaky so molecules can cross
between adjacent cells

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●Ex. epithelial cells of capillaries to allow ions and small molecules, but not blood cells, to
pass out of the blood into the surrounding extracellular fluid
β—†Cover exposed body surfaces and surfaces of internal organs, line cavities and ducts within body
β—†Protect body surfaces from abrasion/ invasion by bacteria and viruses
β—†Some epithelial cells in epidermis of vertebrates contain a network of keratin- family of fibrous
proteins
●Keratin forms protective structures- nails, hair, claws, hooves, horns, feathers, scales
β—†Surface epithelium of arthropods secretes tough cuticle that forms barrier to environment and
serves as animal’s skeleton
β—†Apical surface: outer surface of epithelial cells, may be exposed to water, air, or fluids within
body
●Often covered with cilia in internal cavities, beat like oars to move fluids through cavity
β—†Basal surface: inner surface of epithelial cells, adheres to layer of ECM secreted by epithelial
cells called basal lamina- fixes the epithelium to underlying tissues, often connective tissues
β—†Lining of small intestine- free surface is crowded with microvilli, fingerlike extensions of plasma
membrane that increases the area available for secretion or absorption
β—†Types of epithelia
●Simple- formed by a single layer of cells
●Stratified- formed by multiple cell layers
β—†Shapes of epithelia
●Squamous- mosaic, flattened, spread out
●Cuboidal- shaped like dice, cubes
●Columnar- elongated, with long axis perpendicular to epithelial layer
β—†Epithelia may contain/give rise to cells that are specialized for secretion
β—†Glands: epithelial tissue-derived structures that are specialized for secreting
●Formed during embryonic development by pockets of epithelial tissue that dip inward
from surface and develop ability to secrete
●Exocrine glands: connecting cells between the secretory gland cells and the epithelial
surface cells remain to form a duct between gland and surface
β—‹Secrete substances to outside of the body into cavity that opens to the outside
β—‹Mucus, saliva, digestive enzymes, sweat, earwax, oils, milk, venom
●Endocrine glands: connective cells disappear during development, leaving secretory
gland ductless and isolated from surface
β—‹Release hormones directly into interstitial fluid to be picked up and distributed by
circulatory system
β—‹Pituitary, adrenal, thyroid gland
βž”Connective tissue: tissue having cells scattered through an ECM, forms layers in and around body
structures that support other body tissues, transmit mechanical and other forces, and in some cases act as
filters
β—†Many forms have more ECM material than cellular material
β—†Mechanical properties depend on type and quantity of its ECM
●Consistency of ECM ranges from fluid (blood) through soft gel (tendons) to hard (bone)
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β—†ECM mostly consists primarily of collagen (fibrous glycoprotein) embedded in network of
proteoglycans- glycoproteins that are very rich in carbohydrates
●Collagen is the most abundant family of proteins in animals and is found in all
eumetazoans
β—†In bone, glycoprotein network surrounding collagen is impregnated with mineral deposits that
produce a hard, but elastic, structure
β—†Fibronectin: family of glycoproteins, aids in attachment of cells to the ECM and helps hold cells
in position
β—†Elastin: rubbery protein, adds elasticity to ECM, able to return to original shape after being
stretched, bent, or compressed
●Help skin return to original shape, give lungs elasticity needed for alternating
inflation/deflation
β—†Resilin: protein found only in insects and some crustaceans, most elastic material known
●Basis for jumping of fleas, crickets, locusts
β—†Vertebrates have 6 major types of connective tissues
●Loose connective tissue: consists of sparsely distributed fibroblast cells (cells that secrete
most of the collagen and other proteins) surrounded by a network of collagen and other
glycoprotein
β—‹Support epithelia
β—‹Form corset-like band around blood vessels, nerves, and some internal organs
β—‹Reinforce deeper layers of skin
β—‹Form mesenteries- hold abdominal organs in place and provide lubricated, smooth
surfaces that prevent abrasion to adjacent structures as the body moves
●Dense connective tissue: fibroblasts are sparsely distributed among dense masses of
collagen and elastin fibers that are arranged to resist stretch and provide strength
β—‹Fibers are sometimes arranged irregularly to resist stretch in specific directions
(dermis of skin, covering of muscles, walls of digestive tract)
β—‹Fibers are sometimes lined up in highly ordered, parallel bundles to give tissue a
fibrous appearance under the microscope, produces maximum tensile strength and
elasticity (tendons- attach muscles to bones, ligaments- connect bones to each
other at a joint)
●Cartilage: consists of sparsely distributed chondrocytes (cartilage-producing cells)
surrounded by network of collagen fibers embedded in a tough but elastic matrix of the
glycoprotein chondroitin sulfate
β—‹Elasticity allows it to resist compression and stay resilient like rubber
β—‹Supports larynx, trachea, smaller air passages in the lungs
β—‹Disks cushioning vertebrae in spinal column
●Bone: densest form of connective tissue, forms the skeleton which supports the body,
protects softer body structures (brain) and contributes to body movements
β—‹Mature bone consists mostly of osteocytes- cells embedded in ECM containing
collagen fibers and glycoproteins impregnated with hydroxyapatite
(calcium-phosphate mineral)
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