Download - Chapter 3 cells and tissues
CHAPTER 3CELLS AND TISSUES
Cells – Cell Theory In 1665, and English scientist named
Robert Hooke looked at empty cork cells and identified the first cells
he used the word cell to describe the empty spaces in the cork
Cells – Cell Theory Robert Brown was the first
person to discover the nucleus: the cell part that controls most of the cell’s activities
Two German biologists Mathias Schleiden and Theodor Schwann formed the theory that all plants and animals are made up of cells
Cells – Cell Theory All these ideas combined into the
modern Cell Theory: 1. All living things are made of one or
more cells 2. Cells are the basic units of structure
and function 3. All cells come from existing cells
Cells – The basics All cells are primarily made of four
elements: Carbon, Oxygen, Hydrogen, Nitrogen
Living cells are about 60% water
Cells – Interstitial Fluid In addition to large amounts of water,
the body cells are constantly covered in a dilute saltwater solution called interstitial fluid
This fluid is derived from blood
Two main types of cells
Prokaryotic Cells Eukaryotic Cells
“pro” means before More primitive Lack a nucleus DNA is free floating
“eu” means true More complex Have a nucleus that
contain DNA Have organelles (“tiny
organs”)
What type of cell is this?
What about this one?
Cells – The generalized cell No one cell type is exactly like another Most do have the same parts Let’s talk about a generalized cell: a
basic cell used to demonstrate most cell features
Cells – The generalized cell
Cells – The generalized cell
The cell – The nucleus Nucleus: controls all of the cell’s
activities Contains DNA The “boss” of the cell Determines how and when
proteins are made Controls cell reproduction The nucleus usually conforms to
the shape of the cell
The cell – the nucleus Is enclosed by a nuclear membrane (or
nuclear envelope) Nuclear membrane: structure that
surrounds the nucleus and separates it from the rest of the cell
Nuclear pores: openings in the nuclear membrane that allows molecules to pass
Nucleoplasm: the jelly-like fluid between the two layers of the nuclear membrane
The cell – the nucleus Nucleolus: the center of the nucleus Some cells contain multiple nucleoli Contains the DNA Helps makes ribosomes Contains chromatin
The cell – the nucleus
Chromatin: a loose network of DNA combined with protein scattered throughout the nucleus
When a cell is dividing, the Chromatin condenses and coils to form chromosomes
Chromosomes: threadlike structures with information that determines traits a living thing will have
The cell – the nucleus
The cell – the plasma membrane
The cell – the plasma membrane Plasma membrane: a fragile, transparent barrier
that contains the cell contents and separates them from the surrounding environment
It is semi-permeable or selectively permeable which means it allows some things to pass while blocking others
The cell – the plasma membrane The plasma
membrane is a phospholipid bilayer
This means it has two layers of fats that line up tail to tail
The cell – the plasma membrane The phospholipids each
have a hydrophilic and a hydrophobic end
This allows the membrane to reseal itself quickly when damage occurs
A substantial amount of cholesterol is also found in the plasma membrane
The cell – the plasma membrane The proteins scattered in the lipid bilayer
are responsible for most of the membrane’s specialized functions
Ex. enzymes, hormone receptors, binding sites, protein channels, etc
The cell – Specializations of the plasma membrane
Let’s talk about microvilli and membrane junctions
Microvilli: tiny fingerlike projections that greatly increase the cell’s surface area to increase the rate of absorption
The cell – specializations of the plasma membrane Membrane junctions: specialized
connections between plasma membranes
Three main types are: 1. Tight junctions 2. Desmosomes 3. Gap junctions
The cell – membrane junctions 1. Tight junctions: impermeable junctions
that bind cells together into leakproof sheets that prevent substances from passing through the extracellular space between cells
Plasma membranes fuse together like a zipper
Ex. in the small intestine, these junctions prevent digestive enzymes from seeping into the bloodstream
The cell – membrane junctions Tight Junction
The cell – membrane junctions 2. Desmosomes: anchoring junctions that
prevent cells subjected to mechanical stress from being pulled apart
Structurally these junctions are buttonlike thickenings of adjacent plasma membranes (plaques), connected by fine protein filaments
Thicker protein filaments extend from the plaques inside the cells to the plaques on the cells’ opposite side, forming an internal system of strong wires
Ex. skin cells
The cell – membrane junctions Desmosomes
The cell – membrane junctions 3. Gap junctions: common to heart cells and
embryonic cells, these junctions function mainly to allow communication
Chemical molecules (nutrients, ions, etc) pass directly from one cell to another through the gap
In gap junctions, the neighboring cells are connected by connexons: hollow cylinders composed of proteins that span the entire width of the adjoining membranes
The cell – membrane junctions Gap junctions
The cell – the cytoplasm Cytoplasm: the cellular material outside
the nucleus and inside the plasma membrane
It is where most chemical reactions occur inside the cell
Made of three major elements: 1. the cytosol 2. the organelles 3. inclusions
The cell – the cytoplasm The cytosol is the semitransparent fluid
that suspends the other elements The organelles or “tiny organs” are the
machinery of the cell Inclusions are chemical substances that
may or may not be present, depend on the cell typeInclude stored nutrient, lipids, glycogen,
mucus, various crystallized products, etc
The cell – the cytoplasm
Organelles - Mitochondria Mitochondria: energy-producing
organelle in animal cells Consists of two membranes The outer is smooth and featureless The inner contains shelflike protrusions
called cristae
Organelles – Mitochondria Break down food through the
process of cellular respiration to form ATP molecules
ATP molecules provide the energy for all cellular work
“Busy” cells such as liver and muscles cells have larger amounts of mitochondria
Organelles - Ribosomes Ribosomes: tiny, bilobed, dark bodies
made of proteins and RNA Site of protein synthesis in the cell Two types:
Free – free floating in the cellBound/Attached – attached to the
Endoplasmic Reticulum
Organelles - Ribosomes Ribosomes: tiny particles of RNA and
protein The sight of protein synthesis Two types:
1. Free – free-floating in the cytoplasm2. Bound/Attached – found on the rough
Endoplasmic Reticulum
Organelles – Endoplasmic Reticulum Endoplasmic Reticulum: a system of
fluid-filled sacs and membranes located near the nucleus that packages and exports protein, lipids and other small molecules.
Accounts for about half of a cell’s membrane
Organelles – Endoplasmic Reticulum Endoplasmic Reticulum: a system of
fluid-filled canals (cisterns) that coil and twist through the cytoplasm
Accounts for about half the cell’s membranes
Provides a network of channels for carrying substances
Organelles – Endoplasmic Reticulum Two forms of the ER: 1. Rough ER: studded with ribosomes
All of the building materials of cellular membranes are formed either in or on it:
Proteins are packaged and sent out in transport vesicles
Greater number in organs that require more proteins,○ Ex. pancreas
Organelles – Endoplasmic Reticulum 2. Smooth ER: plays no role in protein
synthesis Functions in lipid metabolism and
detoxification Therefore there are many smooth ER in
liver cells
Organelles – Endoplasmic Reticulum
Organelles – Golgi Apparatus Golgi Apparatus: flattened stack of
membranous sacs that modifies and packages proteins and lipids
Forms secretory vesicles including lysosomes
Organelles - Lysosomes Lysosomes: small, enzyme-filled
organelles Digest worn-out cell structures, foreign
substances, etc Many in phagocytes, cells that dispose
of bacteria and debris
Organelles - Peroxisomes Peroxisomes: mebranous sacs
containing powerful oxidase enzymes that use molecular oxygen to detoxify a number of harmful or poisonous substances
Most important function is to “disarm” free radicals
Organelles - Peroxisomes Free radicals: highly reactive chemicals
with unpaired electrons that can scramble the structure of proteins and nucleic acids
Free radicals are usually produced by cellular respiration but if they accumulate they have devastating effects on the cell
Organelles - Peroxisomes Peroxisomes convert free radicals to
hydrogen peroxide Are created by budding from the Golgi
apparatus
Organelles - Cytoskeleton Cytoskeleton: an elaborate network of
protein the cell’s “bones and muscles” Determine:
Cell shapeSupports the organellesProvides the machinery needed for
intracellular transport and various types of cellular movement
Organelles - Cytoskeleton 3 types of cytoskeleton: 1. Microfilaments
Involved in cell motility and changes in cell shape
2. MicrotubulesDetermine the overall shape of a cell and
the distribution of organelles 3. Intermediate Filaments
Help form desmosomes, resist pulling forces on the cell
Organelles - Cytoskeleton
Organelles - Cytoskeleton Centrioles: rod-shaped bodies that lie at
right angles to each other Made up of fine microtubules Best known for their role in cell division (direct the formation of the mitotic
spindle)
Organelles - Cytoskeleton Some cells have projections known as
cilia and flagella Cilia: whiplike cellular extensions that
move substances along the cell surfaceEx. ciliated respiratory cells moving mucus
Flagella: substantialy longer projections formed by the centriolesonly flagellated human cell is a sperm cell
Organelles - Cytoskeleton
Cell Diversity
Cell Diversity 1. Cells that connect body parts 2. Cell that covers and lines body organs 3. Cells that move organs and body parts 4. Cells that stores nutrients 5. Cells that fight disease 6. Cells that gather information and controls
body functions 7. Cells of reproduction
1. Cells that connect body parts Fibroblast: most common connective
cells in animals Elongated shape Secretes cable-like fibers Produce large amounts of collagen Abundant rough ER and large Golgi
Apparatus (make and secrete necessary proteins
Important in wound healing
1. Cells that connect body parts Erthrocyte: red blood cell Carries oxygen in the bloodstream Concave disk shape
Extra surface area So much oxygen-carrying pigment
(hemoglobin) is packed in that other organelles have been excluded to make room
2. Cells that cover and line body organs
Epithelial cell Hexagonal shape Allows cells to pack
together Many intermediate
filaments that resist tearing
3. Cells that move organs and body parts Skeletal muscle and smooth muscle
cells Elongated Filled with many contractile filaments
Can shorten with great force○ Moves bone○ Change size of internal organs
4. Cells that store nutrients Fat cell (adipose cell) Large and spherical Produced by large lipid droplets in the
cytoplasm
5. Cells that fight disease Macrophage (phagocytic cell) Long, extendable pseudopods (“false
feet”) Crawl through tissue to reach infection
sites Lysosomes within the cell digest the
infectious microorganisms
6. Cells that gather information and control body functions Nerve cell (neuron) Has long processes for receiving and
transmitting messages Processes are covered with an
extensive plasma membrane Large rough ER to synthesize
membrane components
7. Cells of reproduction Oocyte (female): egg cell Largest cell in the body Contains several copies of all organelles
7. Cells of reproduction Sperm (male) Long and streamlined (built for
swimming) Flagellum acts as a motile whip to
propel the sperm
CELL PHYSIOLOGY
Membrane Transport The fluid environment on both sides of
the plasma membrane is an example of a solution.
Solution: a homogeneous mixture of two or more components
Membrane Transport - solutions Every solution is made of two major
components – a solvent and solutes Solvent: the substance present in the
largest amount that does the dissolvingUsually a fluid (liquid or gas)
Solute(s): the substance(s) present in smaller amount that get dissolved
Membrane Transport
Intracellular Fluid: a solution containing small amounts of gases, nutrients, and salts dissolved in water
Interstitial Fluid: the fluid that continuously bathes the exterior of our cellsA rich, nutritious “soup”Contains amino acids, sugars, fatty acids, vitamins, etc
Membrane Transport Quick reminder! Plasma membranes are selectively or
semi-permeable This means they let some things pass
while blocking others
Membrane Transport Movement of substances through the
plasma membrane happens two ways1. Passive Transport2. Active Transport
Passive Transport Passive Transport: movement in which
substances are transported across the membrane without energy input from the cell
Passive Transport Diffusion: the
movement of particles from an area of high concentration to an area of low concentration
High to Low, Go with the Flow!
Passive Transport The particles are said to
move down their concentration gradient: the gradual change in the concentration of solutes in a solution
Speed of diffusion is affected by the size of the molecules (smaller = faster) and temperature (warmer = faster)
Passive Transport The hydrophobic core of the plasma
membrane makes it a physical barrier to diffusion
Particles will still diffuse if:1. they are small enough to pass through
the membrane pores2. they can dissolve in the fatty portion of
the membrane 3. they are assisted by a membrane carrier
Passive Transport Simple diffusion:
unassisted diffusion of solutes through the plasma membrane
Facilitated diffusion: provides passage for certain needed substances that are both lipid-insoluble and too large to pass through the pores
Passive Transport Although facilitated diffusion follows the
laws of diffusion, a protein membrane channel is used
This acts as a transport vehicle
Passive Transport Substances that
pass into and out of cells by diffusion save energy
Includes the movement of key molecules like water, glucose, oxygen and carbon dioxide
Passive Transport Osmosis: the diffusion of water
across a selectively permeable membrane
Remember water is highly polar and is repelled by the non-polar core of the membrane, so it must pass through aquaporins
aquaporins: special pores created by membrane proteins that allow osmosis to occur
Passive Transport Filtration: the process by which water
and solutes are forced through a membrane by fluid, or hydrostatic pressure
In the body, this is usually seen in blood
Passive Transport This is a passive process The gradient however, is the pressure
gradient that pushes solute-containing fluid (the filtrate) from high-pressure areas to low pressure areas
Important to kidneys
Active Transport Whenever a cell uses some of its ATP
supply to move substances across the membrane, the process is considered active
Active Transport: also called solute pumping, requires ATP –energized protein carriers to transport substances across the membrane
Active Transport The ATP-energized protein carriers used
in active transport are called solute pumps Amino acids, some sugars, and most ions
are transported across the membrane in this way
And in most cases, they travel against the concentration gradient
This is opposite to the direction in which substances would normally flow
Active Transport Movement against the concentration
gradient requires energy (ATP) Ex. Sodium-Potassium Pump Simultaneously carries Sodium (Na+)
ions out of the cell and Potassium (K+) ions into the cell
The Na-K Pump is essential for normal nerve cell transmissions
Active Transport
Vesicular Transport Vesicular transport: moves substances
in or out of cells without their actually crossing the plasma membrane
Requires ATP
Vesicular Transport Two main types:
1. Endocytosis2. Exocytosis
Vesicular Transport
Endocytosis Exocytosis
Endocytosis take up, or engulf, extracellular substances by enclosing them in a small membrane vesicle
Once the vesicle, or sac, is formed, it detaches from the plasma membrane and moves into the cytoplasm, where it fuses with a lysosome and its contents are digested
Exocytosis moves substances out of cells
Is how cells actively secrete hormones, mucus and other products
Products are packed in small vesicles or sac
The sac migrates to the plasma membrane and fuses
The contents are then spilled outwards
Vesicular Transport Three types of endocytosis: 1. phagocytosis: “cell eating”
Ingestion of solid substances 2. pinocytosis: “cell drinking”
Ingestion of liquid substances 3. Receptor-mediated endocytosis: main
cellular mechanism for taking up specific target moleculesBoth receptor and the target molecule are taken
into the vesicle
Vesicular Transport
CELL DIVISIONMITOSIS
Cell Division The cell life cycle is the series of
changes a cell goes through from the time it is formed until it divides
The cycle has two major periods: 1. Interphase, in which the cell grows
and carries on it usual metabolic activities
2. Cell Division, time when the cell reproduces itself
Cell Division – Cell Cycle
Cell Division - Interphase Interphase has three major stages 1. G1 – Growth 1
Cell increases in size 2. S – Synthesis
DNA and organelles are replicated 3. G2 – Growth 2
Continued cell growth before division
Cell Division - Interphase
Cell Division Mitosis: division of the nucleus Cytokinesis: division of the cytoplasm
Cell Division Mitosis is divided into
four major phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase And results in two
identical daughter cells
1. Prophase As cell division begins, the chromatin
threads condense to form barlike bodies called chromosomes (“colored bodies”)
1. Prophase The centrioles separate from each other
and begin to move to opposite sides (“poles”) of the cell
The direct the assembly of the mitotic spindle
The mitotic spindle provides the structure for attachment and movement of the chromosomes for the duration of mitosis
1. Prophase The nuclear envelope and nucleoli break
down and disappear Chromosome attach randomly to spindle
fibers at the centromere
2. Metaphase The chromosome cluster and align
along the metaphase plate (center of the spindle midway)
Creates a straight line of chromosomes
3. Anaphase The centromeres split The sister chromatids split (now called
chromosomes again) Chromatids move to opposite poles of the
cell When chromosome movement ends
4. Telophase Essentially prophase in reverse Chromosomes uncoil and become
chromatin again Spindle fibers break down and
disappear Nuclear envelopes reform and nucleoli
reappear around each group of chromatin
4. Telophase
Cytokinesis Cytokinesis usually begins during late
anaphase and finishes in telophase A contractile ring of microfilaments forms
a cleavage furrow over the midline of the spindle
This squeezes the original cytoplasmic mass into two parts
Each daughter cell is smaller, but genetically identical
Cytokinesis
Mitosis and Cytokinesis Mitosis and Cytokinesis usually go
together, but sometimes the cytoplasm does not divide
This creates binucleated or multinucleated cells
This is common in liver cells
PROTEIN SYNTHESISTranscription and Translation
Protein Synthesis DNA is the blueprint for protein
synthesis A gene is defined as the DNA segment
that carries the information for building one protein of a poly peptide chain
Protein Synthesis - RNA DNA requires a messenger and a
decoder to complete the building of proteins
These jobs are carried our by RNA There are three varieties of RNA
involved in protein synthesis:1. transfer RNA (tRNA)2. ribosomal RNA (rRNA)3. messenger RNA (mRNA)
Protein Synthesis Protein Synthesis occurs in two major
phases:1. Transcription – when complementary
mRNA is made at the DNA gene2. Translation – when the information carried
in the mRNA molecules is “decoded” and used to assemble proteins
Protein Synthesis - Transcription Transcription involves the
transfer of information from DNA’s base sequence into the complementary base sequence of mRNA
Occurs in the nucleus Only DNA and mRNA are
involved in transcription Each DNA triplet (three-base
sequence) complements a mRNA codon
Protein Synthesis - Transcription So if the DNA sequence is: ATG – TCT – GAA (triplets) The transcribed mRNA sequence is: UAC – AGA – CUU (codons)
Protein Synthesis - Translation In translation the language
of nucleic acids (the base sequence) is “translated” into the language of proteins (amino acids)
Occurs in the cytoplasm Involves three major
varieties of RNA
Protein Synthesis - Translation Once the mRNA attaches to the
ribosome, tRNA comes into the picture Each tRNA carries or “transfers” an
amino acid to the ribosome They match a three-base anticodon
with the codon of the mRNA as it reads through the ribsome
Protein Synthesis - Translation
Protein Synthesis - Translation Once the first tRNA has moved itself into the
correct position, the ribosome moves the mRNA strand along, bringing the next codon into position to be read by the tRNA
As each amino acid is brought in, they are joined together by enzymes
As the amino acids join, each tRNA is released
When the last codon, or “stop” codon is read, the protein is released
Protein Synthesis
BODY TISSUES
Body Tissues Tissues: groups of cells that are similar
in structure and function Four primary tissue types: 1. Epithelial (covering) 2. Connective (support) 3. Muscular (movement) 4. Nervous (control)
Epithelial Tissues Epithelial Tissue (epithelium): the lining,
covering and glandular tissue of the body
Helps form boundaries and separate Nearly all substances the body gives off
or receives must pass through the epithelium
Epithelial Tissues Functions of the epithelium: Protection Absorption Filtration Secretion
Epithelial Tissues - Characteristics 1. Fit closely together (except glandular cells)
Bound together by many desmosomes and tight junctions
2. One free edge or surfaceApical surface
3. Lower surface rests on a basement membrane
4. No blood supply of their ownAvascularDepend on diffusion from the capillaries
5. Regenerate themselves, if well nourished
Epithelial Tissues - Classification Each epithelium is given two names The first indicates the relative number of
cell layers
Epithelial Tissues - Classification The classifications by cell arrangement are: Simple epithelium – one layer Stratified epithelium – more than one layer
Epithelial Tissues - Classification The second indicates the shape of the
cell. There are: Squamous – flattened like scales Cuboidal – Cube-shaped Columnar – Column-shaped (stratified epithelia are named for the
cells at the free surface not those on the basement membrane)
Epithelial Tissues - Classification
Epithelial Function Simple Epithelia are concerned mainly
with absorption, secretion and filtration
Stratified epithelia function primarily to protect
Glandular Epithelium A gland consists of one or more cells
that make and secrete a particular product
This product is called a secretion Usually consists of protein molecules in
an aqueous solution fluid
Glandular Epithelium Two major types of glands develop from
epithelial sheets: 1. Endocrine glands 2. Exocrine glands
Endocrine Glands Endocrine glands: glands
that lose their connection to the surface or duct (also called ductless glands)
Secretions diffuse directly into the blood vessels that weave through the gland
Ex. thyroid, adrenals, pituitary
Exocrine Glands Exocrine glands:
gland that retain their ducts
Secretions empty through the ducts to the epithelial surface
Ex. sweat and oil glands, liver, pancreas
Glandular Epithelium The term secretion
also indicates an active process in which the glandular cells obtain needed materials from the blood and use them to make their secretion, which they then discharge
CONNECTIVE TISSUE
Connective Tissue Connective Tissue: connects body parts Found everywhere in the body Most abundant and widely distributed of
the tissue types
Connective Tissue The characteristics of connective tissue
include: 1. Variations in blood supply
Most connective tissue is well vascularizedExceptions – Ligaments, Tendons, Cartilages
○ As a result these heal very slowly 2. Extracellular Matrix
Varying amounts of a nonliving substance outside the cells
Connective Tissue The extracellular matrix distinguishes
connective tissue from other cell types Has two main elements – a structureless
ground substance and fibers
Connective Tissue The ground substance of the matrix is
composed largely of water plus some adhesion proteins and large, charged polysaccharides
The adhesion proteins are the “glue” that allows the connective tissues to attach themselves to matrix fibers embedded in the ground substance
The charged polysaccharides trap water as they intertwine
Connective Tissue Various types and amounts of fibers are
in the matrix and form parts of the matrix itself
Including collagen (white) fibers, elastic (yellow) fibers and reticular (fine collagen) fibers
Connective Tissues Because of the extracellular matrix,
connective tissue can form soft packing tissue around organs, bear weight, and withstand stretching and other abuses
Connective Tissue There is great variation in connective
tissue The major classes are: Bone Cartilage Dense Connective Loose Connective Blood
Connective Tissue - Bone Bone (osseous tissue) Composed on bone cells sitting in
cavities called lacunae (pits) and surrounded by layers of a very hard matrix that contains calcium salts and large numbers of collagen fibers
Important in protecting and supporting other body organs
Connective Tissue - Bone
Connective Tissue - Cartilage Less hard and more flexible than bone Found a few places in the body Most widespread is hyaline cartilage:
abundant collagen fibers hidden by a rubbery matrix with a glassy blue-white appearance
Connective Tissue - Cartilage Forms supporting structures in the
larynx, attaches ribs to the breastbone, covers ends of bones at joints
Connective Tissue There are other types of cartilage: Fibrocartilage: highly compressible that
forms the cushionlike disks between the vertebrae of the spinal column
Elastic cartilage: is found where a structure where elasticity is desired
Ex. external ear
Connective Tissue Dense Connective Tissue:
collagen fibers as its main matrix element
Crowded between the collagen fibers are rows of fibroblasts that manufacture the building blocks of the fibers
Forms tendons and ligaments
Connective Tissue Tendons: attach skeletal muscles to
bones Ligaments: connect bones to bones at
joints Ligaments are more stretchy and elastic
than tendons
Connective Tissue Loose Connective Tissue: softer, have
more cells and fewer fibers Areolar Tissue: most widely distributed
connective tissue variety in the body Cushions and protects body organs
Connective Tissue When a body region is inflamed, the
areolar tissue in the area soaks up the excess fluid like a sponge, and the area swells and becomes puffy
This is called an edema
Connective Tissue Adipose Tissue:
commonly called fat, areolar tissue in which fat cells predominate
Forms subcutaneous tissue
Connective Tissue Reticular connective tissue: a delicate
network of interwoven reticular fibers associated with reticular cells, which resemble fibroblasts
Forms stroma, the internal framework which can support many free blood cells and in lymphoid organs
Connective Tissue Blood: (vascular tissue) is
considered connective tissue because it consists of blood cells surrounded by nonliving, fluid matrix called blood plasma
The “fibers” of blood are soluble protein molecules that become visible only during blood clotting
Muscle Tissue Muscle tissue: highly specialized to
contract, or shorten, to produce movement
Muscle Tissue Three main types: 1. skeletal muscle 2. cardiac muscle 3. smooth muscle
Muscle Tissue Skeletal Muscle attached to the skeleton can be controlled voluntarily when contracted they pull on
bones or skin the cells of skeletal muscle
are long, cylindrical, multinucleate and have obvious striations
Muscle Tissue Cardiac Muscle Found only in the heart As it contracts, the heart acts as a pump and
propels blood through the blood vessels Has striations Uninucleate, relatively short, branching, and
fit tightly together through intercalated disks Under involuntary control
Muscle Tissue
Muscle Tissue Smooth Muscle (visceral muscle) No visible striations Single nucleus, spindle-shaped Found in the walls of hollow organs As it contracts, the cavity of an organ
contracts or enlarges Contracts more slowly than the other two
types Ex. peristalsis
Nervous Tissue Think neurons All neurons receive and conduct
electrochemical impulses from one part of the body to another
Irritability and conductivity are their two major functional characteristics
Nervous Tissue Drawn out cytoplasm, allow for long
signal transmission With supporting cells, neurons make up
the structures of the nervous system
TISSUE REPAIR
Tissue Repair Tissue repair occurs in two major ways: Regeneration – replacement of
destroyed tissue by the same kind of cells
Fibrosis – involves repair by dense connective tissue by the formation of scar tissueDepends on the type of tissue damaged and
the severity of the injury
Tissue Repair Tissue injury sets the following steps in
motion: 1. capillaries become permeable
Fluid rich in clotting proteins seep into the injured areas
2. granulation tissue formsDelicate pink tissue composed largely of new
capillaries 3. surface epithelium regenerates
Makes its way across the granulation tissue
Tissue Repair
Three other important terms: Neoplasm: an abnormal mass of
proliferating cells Benign or malignant
Hyperplasia: when certain body tissues may enlarge because there is some local irritant or condition that stimulates the cells
Atrophy: a decrease in size in an organ or body area that loses its normal stimulation