Ch.3: Cells and Tissues Flashcards
1
Q
Cells
A
- Cells are the structural units of all living things
* The human body has 50 to 100 trillion cells
2
Q
The Cell Theory
A
- A cell is the basic structural and functional unit of living organisms
- The activity of an organism depends on the collective activities of its cells
- According to the principle of complementarity, the biochemical activities of cells are dictated by their structure (anatomy) which determines their function (physiology)
- Continuity of life has a cellular basis
3
Q
Most cells are composed of four elements:
A
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
4
Q
What percentage of a cell is water?
A
60%
5
Q
In general, a cell has three main regions or parts:
A
- Nucleus
- Cytoplasm
- Plasma membrane
6
Q
The nucleus
A
• Control center of the cell
7
Q
The nucleus contains genetic material known as:
A
- Deoxyribonucleic acid, or DNA
- DNA is needed for building proteins
- DNA is necessary for cell reproduction
8
Q
Three regions of the nucleus:
A
- Nuclear envelope (membrane)
- Nucleolus
- Chromatin
9
Q
Nuclear envelope (membrane)
A
- Consists of a double membrane that bounds the nucleus
- Contains nuclear pores that allow for exchange of material with the rest of the cell
- Encloses the jellylike fluid called the nucleoplasm
10
Q
Nucleolus
A
- Nucleus contains one or more dark-staining nucleoli
- Sites of ribosome assembly
- Ribosomes migrate into the cytoplasm through nuclear pores to serve as the site of protein synthesis
11
Q
Chromatin
A
- Composed of D N A wound around histones (proteins)
- Scattered throughout the nucleus and present when the cell is not dividing
- Condenses to form dense, rod-like bodies called chromosomes when the cell divides
12
Q
Plasma Membrane
A
- Transparent barrier for cell contents
- Contains cell contents
- Separates cell contents from surrounding environment
13
Q
Fluid mosaic model is constructed of:
A
- Two layers of phospholipids arranged “tail to tail”
- Cholesterol and proteins scattered among the phospholipids
- Sugar groups may be attached to the phospholipids, forming glycolipids
14
Q
Concept Link 1
A
Remember, phospholipids are polar molecules: The charged end interacts with water, and the fatty acid chains do not (see Chapter 2, p. 46). It is this property of polarity that makes phospholipids a good foundation for cell membranes.
15
Q
Phospholipid arrangement in the plasma membrane:
A
• Hydrophilic (“water loving”) polar “heads” are oriented on the inner and outer surfaces of the membrane
• Hydrophobic (“water fearing”) nonpolar “tails” form the center (interior) of the membrane
This interior makes the plasma membrane relatively impermeable to most water-soluble molecules
16
Q
Role of proteins:
A
Responsible for specialized membrane functions:
• Enzymes
• Receptors for hormones or other chemical messengers
• Transport as channels or carriers
17
Q
Role of sugars:
A
- Glycoproteins are branched sugars attached to proteins that abut the extracellular space
- Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell’s surface
18
Q
Cell membrane junctions
A
Cells are bound together in three ways:
- Glycoproteins in the glycocalyx act as an adhesive or cellular glue
- Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion
- Special cell membrane junctions are formed, which vary structurally depending on their roles
19
Q
Main types of cell junctions:
A
- Tight junctions
- Desmosomes
- Gap junctions (communicating junctions)
20
Q
Tight junctions
A
- Impermeable junctions
- Bind cells together into leakproof sheets
- Plasma membranes fuse like a zipper to prevent substances from passing through extracellular space between cells
21
Q
Desmosomes
A
- Anchoring junctions, like rivets, that prevent cells from being pulled apart as a result of mechanical stress
- Created by buttonlike thickenings of adjacent plasma membranes
22
Q
Gap junctions (communicating junctions)
A
- Allow communication between cells
- Hollow cylinders of proteins (connexons) span the width of the abutting membranes
- Molecules can travel directly from one cell to the next through these channels
23
Q
Cytoplasm
A
- The cellular material outside the nucleus and inside the plasma membrane
- Site of most cellular activities
- Includes cytosol, inclusions, and organelles
24
Q
Three major components of cytoplasm
A
- Cytosol: Fluid that suspends other elements and contains nutrients and electrolytes
- Inclusions: Chemical substances, such as stored nutrients or cell products, that float in the cytosol
- Organelles: Metabolic machinery of the cell that perform functions for the cell
• Many are membrane-bound, allowing for compartmentalization of their functions
25
Mitochondria
* “Powerhouses” of the cell
* Mitochondrial wall consists of a double membrane with cristae on the inner membrane
* Carry out reactions in which oxygen is used to break down food into ATP molecules
26
Ribosomes
* Made of protein and ribosomal R N A
| * Sites of protein synthesis in the cell
27
Ribosomes are found at two locations:
* Free in the cytoplasm
| * As part of the rough endoplasmic reticulum
28
Endoplasmic reticulum (ER)
* Fluid-filled tunnels (or canals) that carry substances within the cell
* Continuous with the nuclear membrane
29
The two types of endoplasmic reticulum (ER):
* Rough ER
| * Smooth ER
30
Rough endoplasmic reticulum (ER)
* Studded with ribosomes
* Synthesizes proteins
* Transport vesicles move proteins within cell
* Abundant in cells that make and export proteins
31
Smooth endoplasmic reticulum (ER)
* Lacks ribosomes
* Functions in lipid metabolism
* Detoxification of drugs and pesticides
32
Golgi apparatus
* Appears as a stack of flattened membranes associated with tiny vesicles
* Modifies and packages proteins arriving from the rough ER via transport vesicles
33
The Golgi apparatus produces different types of packages:
* Secretory vesicles (pathway 1)
* In-house proteins and lipids (pathway 2)
* Lysosomes (pathway 3)
34
Lysosomes
* Membranous “bags” that contain digestive enzymes
* Enzymes can digest worn-out or non-usable cell structures
* House phagocytes that dispose of bacteria and cell debris
35
Peroxisomes
Membranous sacs of oxidase enzymes
• Detoxify harmful substances such as alcohol and formaldehyde
• Break down free radicals (highly reactive chemicals)
• Free radicals are converted to hydrogen peroxide and then to water
36
Peroxisomes replicate by:
Pinching in half or budding from the ER
37
Cytoskeleton
* Network of protein structures that extend throughout the cytoplasm
* Provides the cell with an internal framework that determines cell shape, supports organelles, and provides the machinery for intracellular transport
38
Three different types of elements form the cytoskeleton:
1. Microfilaments (largest)
2. Intermediate filaments
3. Microtubules (smallest)
39
Centrioles
* Rod-shaped bodies made of nine triplets of microtubules
* Generate microtubules
* Direct the formation of mitotic spindle during cell division
40
Surface extensions found in some cells:
* Cilia
* Flagella
* Microvilli
41
Cilia
* Move materials across the cell surface
| * Located in the respiratory system to move mucus
42
Flagella
* Propel the cell
| * The only flagellated cell in the human body is sperm
43
Microvilli
* Tiny, fingerlike extensions of the plasma membrane
| * Increase surface area for absorption
44
The human body houses over:
200 different cell types
45
Cells vary in size, shape, and function
* Cells vary in length from 1/12,000 of an inch to over 1 yard (nerve cells)
* Cell shape reflects its specialized function
46
Cells that connect body parts:
* Fibroblast
| * Erythrocyte (red blood cell)
47
Fibroblast
Secretes cable-like fibers
48
Erythrocyte (red blood cell)
Carries oxygen in the bloodstream
49
Cells that cover and line body organs:
Epithelial cell
50
Epithelial cell
* Packs together in sheets
| * Intermediate fibers resist tearing during rubbing or pulling
51
Cells that move organs and body parts:
Skeletal muscle and smooth muscle cells
| • Contractile filaments allow cells to shorten forcefully
52
Cell that stores nutrients:
* Fat cells
| * Lipid droplets stored in cytoplasm
53
Cell that fights disease:
White blood cells, such as the macrophage (a phagocytic cell)
• Digests infectious microorganisms
54
Cell that gathers information and controls body functions:
```
Nerve cell (neuron)
• Receives and transmits messages to other body structures
```
55
Cells of reproduction:
* Oocyte (female)
| * Sperm (male)
56
Oocyte (female)
* Largest cell in the body
| * Divides to become an embryo upon fertilization
57
Sperm (male)
* Built for swimming to the egg for fertilization
| * Flagellum acts as a motile whip
58
Cells have the ability to:
* Metabolize
* Digest food
* Dispose of wastes
* Reproduce
* Grow
* Move
* Respond to a stimulus
59
Solution
Homogeneous mixture of two or more components
60
Solvent
Dissolving medium present in the larger quantity; the body’s main solvent is water
61
Solutes
Components in smaller quantities within a solution
62
Intracellular fluid
* Nucleoplasm and cytosol
| * Solution containing gases, nutrients, and salts dissolved in water
63
Extracellular fluid (interstitial fluid)
* Fluid on the exterior of the cell
| * Contains thousands of ingredients, such as nutrients, hormones, neurotransmitters, salts, waste products
64
The plasma membrane is a selectively permeable barrier
* Some materials can pass through, while others are excluded
| * For example, nutrients can enter the cell and undesirable substances are kept out
65
Two basic methods of transport:
Passive processes
| Active processes
66
Active processes
* The cell provides the metabolic energy (ATP) to drive the transport process
* ATP is used to move substances across a membrane
* Active transport and vesicular transport
67
Passive processes
* Substances are transported across the membrane without any input from the cell
* Diffusion and filtration
68
Diffusion
* Molecule movement is from high concentration to low concentration, down a concentration gradient
* Particles tend to distribute themselves evenly within a solution
* Kinetic energy (energy of motion) causes the molecules to move about randomly
* Size of the molecule and temperature affect the speed of diffusion
69
Molecules will move by diffusion if any of the following applies:
* The molecules are small enough to pass through the membrane’s pores (channels formed by membrane proteins)
* The molecules are lipid-soluble
* The molecules are assisted by a membrane carrier
70
Types of diffusion
* Simple diffusion
* Osmosis
* Facilitated diffusion
71
Simple diffusion
An unassisted process
| Solutes are lipid-soluble or small enough to pass through membrane pores
72
Osmosis
* Simple diffusion of water across a selectively permeable membrane
* Highly polar water molecules easily cross the plasma membrane through aquaporins
* Water moves down its concentration gradient
* Isotonic solutions have the same solute and water concentrations as cells and cause no visible changes in the cell
* Hypertonic solutions contain more solutes than the cells do; the cells will begin to shrink
* Hypotonic solutions contain fewer solutes (more water) than the cells do; cells will plump
73
Facilitated diffusion
* Transports lipid-insoluble and large substances
* Glucose is transported via facilitated diffusion
* Protein membrane channels or protein molecules that act as carriers are used
74
Filtration
* Water and solutes are forced through a membrane by fluid, or hydrostatic, pressure
* A pressure gradient must exist that pushes solute-containing fluid (filtrate) from a high-pressure area to a lower-pressure area
* Filtration is critical for the kidneys to work properly
75
Active processes are used when:
* Substances are too large to travel through membrane channels
* The membrane may lack special protein carriers for the transport of certain substances
* Substances may not be lipid-soluble
* Substances may have to move against a concentration gradient
76
Active transport
* Amino acids, some sugars, and ions are transported by protein carriers known as solute pumps
* ATP energizes solute pumps
* In most cases, substances are moved against concentration (or electrical) gradients
77
Active transport example: sodium-potassium pump
* Necessary for nerve impulses
* Sodium is transported out of the cell
* Potassium is transported into the cell
78
Vesicular transport:
Substances are moved across the membrane “in bulk” without actually crossing the plasma membrane
79
Types of vesicular transport:
* Exocytosis
| * Endocytosis (phagocytosis and pinocytosis)
80
Exocytosis
* Mechanism cells use to actively secrete hormones, mucus, and other products
* Material is carried in a membranous sac called a vesicle that migrates to and combines with the plasma membrane
* Contents of vesicle are emptied to the outside
* Exocytosis docking process
81
Exocytosis docking process
* Docking proteins on the vesicles recognize plasma membrane proteins and bind with them
* Membranes corkscrew and fuse together
82
Endocytosis
* Extracellular substances are enclosed (engulfed) in a membranous vesicle
* Vesicle detaches from the plasma membrane and moves into the cell
* Once in the cell, the vesicle typically fuses with a lysosome
* Contents are digested by lysosomal enzymes
* In some cases, the vesicle is released by exocytosis on the opposite side of the cell
83
Types of endocytosis
* Phagocytosis
* Pinocytosis
* Receptor-mediated endocytosis
84
Phagocytosis—“cell eating”
* Cell engulfs large particles such as bacteria or dead body cells
* Pseudopods are cytoplasmic extensions that separate substances (such as bacteria or dead body cells) from external environment
* Phagocytosis is a protective mechanism, not a means of getting nutrients
85
Pinocytosis—“cell drinking”
* Cell “gulps” droplets of extracellular fluid containing dissolved proteins or fats
* Plasma membrane forms a pit, and edges fuse around droplet of fluid
* Routine activity for most cells, such as those involved in absorption (small intestine)
86
Receptor-mediated endocytosis
* Method for taking up specific target molecules
* Receptor proteins on the membrane surface bind only certain substances
* Highly selective process of taking in substances such as enzymes, some hormones, cholesterol, and iron
87
Cell life cycle
A series of changes the cell experiences from the time it is formed until it divides
88
Cell life cycle has two major periods:
* Interphase (metabolic phase)
| * Cell division
89
Interphase (metabolic phase)
* Cell grows and carries on metabolic processes
| * Longer phase of the cell cycle
90
Cell division
• Cell reproduces itself
91
Preparations: DNA Replication
* Genetic material is duplicated and readies a cell for division into two cells
* Occurs toward the end of interphase
92
Concept Link 2
Recall that D N A is a very complex molecule (see Chapter 2, p. 53). It is composed of building blocks called nucleotides, each consisting of a deoxyribose sugar, a phosphate group, and a nitrogen-containing base. Essentially, D N A is a double helix, a ladderlike molecule that is coiled into a spiral staircase shape. The upright parts of the D N A “ladder,” or backbone, are alternating phosphate and sugar units, and the rungs of the ladder are made of pairs of nitrogen-containing bases.
93
Process of DNA replication:
* DNA uncoils into two nucleotide chains, and each side serves as a template
* Nucleotides are complementary (adenine (A) always bonds with thymine (T); guanine (G) always bonds with cytosine (C)
* For example, TACTGC bonds with new nucleotides in the order ATGACG
94
Events of cell division:
* Mitosis
| * Cytokinesis
95
Cytokinesis
* Division of the cytoplasm
* Begins when mitosis is near completion, during late anaphase and completes during telophase
* A cleavage furrow (contractile ring of microfilaments) forms to pinch the cells into two parts
* Results in the formation of two daughter cells
96
Mitosis
* Division of the nucleus
| * Results in the formation of two daughter nuclei
97
Events of mitosis: prophase
* Chromatin coils into chromosomes; identical strands called chromatids are held together by a centromere
* Centrioles direct the assembly of a mitotic spindle
* Nuclear envelope and nucleoli have broken down
98
Events of mitosis: metaphase
* Chromosomes are aligned in the center of the cell on the metaphase plate (center of the spindle midway between the centrioles)
* Straight line of chromosomes is now seen
99
Events of mitosis: anaphase
* Centromere splits
* Chromatids move slowly apart and toward the opposite ends of the cell
* Anaphase is over when the chromosomes stop moving
100
Events of mitosis: telophase
* Reverse of prophase
* Chromosomes uncoil to become chromatin
* Spindles break down and disappear
* Nuclear envelope re-forms around chromatin
* Nucleoli appear in each of the daughter nuclei
101
In most cases, mitosis and cytokinesis occur together. In some cases:
* The cytoplasm is not divided
* Binucleate or multinucleate cells result
* Common in the liver and skeletal muscle
102
DNA serves as a blueprint for:
Making proteins
103
Proteins have many functions:
* Fibrous (structural) proteins are the building materials for cells
* Globular (functional) proteins can act as enzymes (biological catalysts)
104
Gene
DNA segment that carries a blueprint for building one protein or polypeptide chain
105
DNA information is coded into a sequence of:
Bases
106
A sequence of three bases (triplet) codes for:
An amino acid
107
The role of DNA
* Most ribosomes, the manufacturing sites of proteins, are located in the cytoplasm
* DNA never leaves the nucleus in interphase cells
* DNA requires a decoder and a messenger to carry instructions to build proteins to ribosomes
* Both the decoder and messenger functions are carried out by RNA (ribonucleic acid)
108
How does RNA differ from DNA?
* RNA is single-stranded
* RNA contains ribose sugar instead of deoxyribose
* RNA contains uracil (U) base instead of thymine (T)
109
Three varieties of RNA:
* Transfer RNA (tRNA)
* Ribosomal RNA (rRNA)
* Messenger RNA (mRNA)
110
Messenger RNA (mRNA)
Carries the instructions for building a protein from the nucleus to the ribosome
111
Ribosomal RNA (rRNA)
Helps form the ribosomes where proteins are built
112
Transfer RNA (tRNA)
Transfers appropriate amino acids to the ribosome for building the protein
113
Protein synthesis involves two major phases:
* Transcription
| * Translation
114
Transcription
* Transfer of information from DNA’s base sequence to the complementary base sequence of mRNA
* DNA is the template for transcription; mRNA is the product
* Each DNA triplet corresponds to an mRNA codon
* If D N A sequence is AAT-CGT-TCG, then the mRNA corresponding codons are UUA-GCA-AGC
115
Translation
* Base sequence of nucleic acid is translated to an amino acid sequence; amino acids are the building blocks of proteins
* Occurs in the cytoplasm and involves three major varieties of RNA
116
Steps of translation
* Step 1: transcription
* Step 2: mRNA leaves nucleus and attaches to ribosome, and translation begins
* Step 3: incoming tRNA recognizes a complementary mRNA codon calling for its amino acid by temporarily binding its anticodon to the codon
* Step 4: as the ribosome moves along the m R N A, a new amino acid is added to the growing protein chain
* Step 5: released t R N A reenters the cytoplasmic pool, ready to be recharged with a new amino acid
117
Concept Link 3
Recall that the joining of amino acids by the ribosome into peptide bonds is the result of dehydration synthesis reactions (Chapter 2, p. 42). To make room for the new peptide bond, water (H2O) must be removed. A hydrogen atom is removed from one amino acid, and a hydroxyl group (OH) is removed from the other.
118
Tissues
Groups of cells with similar structure and function
119
Four primary types of tissues:
* Epithelial tissue (epithelium)
* Connective tissue
* Muscle tissue
* Nervous tissue
120
Epithelial tissue locations:
* Body coverings
* Body linings
* Glandular tissue
121
Epithelial tissue functions:
* Protection
* Absorption
* Filtration
* Secretion
122
Hallmarks of epithelial tissues:
* Cover and line body surfaces
* Often form sheets with one free surface, the apical surface, and an anchored surface, the basement membrane
* Avascular (no blood supply)
* Regenerate easily if well nourished
123
Classification of epithelia
```
Number of cell layers
• Simple—one layer
• Stratified—more than one layer
Shape of cells
• Squamous—flattened, like fish scales
• Cuboidal—cube-shaped, like dice
• Columnar—shaped like columns
```
124
Simple epithelia
* Functions in absorption, secretion, and filtration
| * Very thin (so not suited for protection)
125
Simple squamous epithelium
• Single layer of flat cells
• Locations—usually forms membranes
*Lines air sacs of the lungs
*Forms walls of capillaries
*Forms serous membranes (serosae) that line and cover organs in ventral cavity
• Functions in diffusion, filtration, or secretion in membranes
126
Simple cuboidal epithelium
```
• Single layer of cube-like cells
• Locations
*Common in glands and their ducts
*Forms walls of kidney tubules
*Covers the surface of ovaries
• Functions in secretion and absorption; ciliated types propel mucus or reproductive cells
```
127
Simple columnar epithelium
• Single layer of tall cells
*Goblet cells secrete mucus
• Locations
*Lining of the digestive tract from stomach to anus
*Mucous membranes (mucosae) line body cavities opening to the exterior
• Functions in secretion and absorption; ciliated types propel mucus or reproductive cells
128
Pseudostratified columnar epithelium
* All cells rest on a basement membrane
* Single layer, but some cells are shorter than others giving a false (pseudo) impression of stratification
* Location: respiratory tract, where it is ciliated and known as pseudostratified ciliated columnar epithelium
* Functions in absorption or secretion
129
Stratified epithelia
* Consist of two or more cell layers
| * Function primarily in protection
130
Stratified squamous epithelium
• Most common stratified epithelium
• Named for cells present at the free (apical) surface, which are squamous
• Functions as a protective covering where friction is common
• Locations—lining of the:
*Skin (outer portion)
*Mouth
*Esophagus
131
Stratified cuboidal epithelium
* Two layers of cuboidal cells
| * Functions in protection
132
Stratified columnar epithelium
* Surface cells are columnar, and cells underneath vary in size and shape
* Functions in protection
133
Stratified cuboidal and columnar epithelia
* Rare in human body
| * Found mainly in ducts of large glands
134
Transitional epithelium
* Composed of modified stratified squamous epithelium
* Shape of cells depends upon the amount of stretching
* Functions in stretching and the ability to return to normal shape
* Location: lining of urinary system organs
135
Glandular epithelia
* One or more cells responsible for secreting a particular product
* Secretions contain protein molecules in an aqueous (water-based) fluid
* Secretion is an active process
136
Two major gland types develop from epithelial sheets:
* Endocrine glands
| * Exocrine glands
137
Exocrine glands
* Secretions empty through ducts to the epithelial surface
| * Include sweat and oil glands, liver, and pancreas (both internal and external)
138
Endocrine glands
* Ductless; secretions (hormones) diffuse into blood vessels
| * Examples include thyroid, adrenals, and pituitary
139
Connective tissue
• Found everywhere in the body to connect body parts
• Includes the most abundant and widely distributed tissues
*Functions
*Protection
*Support
*Binding
140
Characteristics of connective tissue:
Variations in blood supply
• Some tissue types are well vascularized
• Some have a poor blood supply or are avascular
Extracellular matrix
• Nonliving material that surrounds living cells
141
Two main elements of the extracellular matrix
```
1. Ground substance
• Mostly water, along with adhesion proteins and polysaccharide molecules
2. Fibers
• Collagen (white) fibers
• Elastic (yellow) fibers
• Reticular fibers (a type of collagen)
```
142
Types of connective tissue from most rigid to softest, or most fluid:
* Bone
* Cartilage
* Dense connective tissue
* Loose connective tissue
* Blood
143
Bone (osseous tissue)
Composed of:
• Osteocytes (bone cells) sitting in lacunae (cavities)
• Hard matrix of calcium salts
• Large numbers of collagen fibers
Functions to protect and support the body
144
Cartilage
```
• Less hard and more flexible than bone
• Found in only a few places in the body
• Chondrocyte (cartilage cell) is the major cell type
• Types
*Hyaline cartilage
*Fibrocartilage
*Elastic cartilage
```
145
Hyaline cartilage
```
• Most widespread type of cartilage
• Abundant collagen fibers hidden by a glassy, rubbery matrix
• Locations
*Trachea
*Attaches ribs to the breastbone
*Covers ends of long bones
*Entire fetal skeleton prior to birth
*Epiphyseal (growth) plates in long bones
```
146
Elastic cartilage
* Provides elasticity
| * Location: supports the external ear
147
Fibrocartilage
* Highly compressible
| * Location: forms cushion-like discs between vertebrae of the spinal column
148
Dense connective tissue (dense fibrous tissue)
```
• Main matrix element is collagen fiber
• Fibroblasts are cells that make fibers
• Locations
*Tendons—attach skeletal muscle to bone
*Ligaments—attach bone to bone at joints and are more elastic than tendons
*Dermis—lower layers of the skin
```
149
Loose connective tissue
```
• Softer, have more cells and fewer fibers than other connective tissues (except blood)
• Types
*Areolar
*Adipose
*Reticular
```
150
Areolar connective tissue
* Most widely distributed connective tissue
* Soft, pliable tissue like “cobwebs”
* Functions as a universal packing tissue and “glue” to hold organs in place
* Layer of areolar tissue called lamina propria underlies all membranes
* All fiber types form a loose network
* Can soak up excess fluid (causes edema)
151
Adipose connective tissue
```
• An areolar tissue in which adipose (fat) cells dominate
• Functions
*Insulates the body
*Protects some organs
*Serves as a site of fuel storage
• Locations
*Subcutaneous tissue beneath the skin
*Protects organs, such as the kidneys
*Fat “depots” include hips, breasts, and belly
```
152
Reticular connective tissue
• Delicate network of interwoven fibers with reticular cells (like fibroblasts)
• Forms stroma (internal framework) of organs
• Locations
*Lymph nodes
*Spleen
*Bone marrow
153
Blood (vascular tissue)
• Blood cells surrounded by fluid matrix known as blood plasma
• Soluble fibers are visible only during clotting
• Functions as the transport vehicle for the cardiovascular system, carrying:
*Nutrients
*Wastes
*Respiratory gases
154
Muscle tissue
```
• Function is to contract, or shorten, to produce movement
• Three types of muscle tissue:
*Skeletal
*Cardiac
*Smooth
```
155
Skeletal muscle tissue
• Packaged by connective tissue sheets into skeletal muscles, which are attached to the skeleton and pull on bones or skin
• Voluntarily (consciously) controlled
• Produces gross body movements or facial expressions
• Characteristics of skeletal muscle cells
*Striations (stripes)
*Multinucleate (more than one nucleus)
*Long, cylindrical shape
156
Cardiac muscle tissue
```
• Involuntarily controlled
• Found only in the heart
• Pumps blood through blood vessels
• Characteristics of cardiac muscle cells
*Striations
*One nucleus per cell
*Short, branching cells
*Intercalated discs contain gap junctions to connect cells together
```
157
Smooth (visceral) muscle tissue
• Involuntarily controlled
• Found in walls of hollow organs such as stomach, uterus, and blood vessels
• Peristalsis, a wavelike activity, is a typical activity
• Characteristics of smooth muscle cells
*No visible striations
*One nucleus per cell
*Spindle-shaped cells
158
Nervous tissue
Function is to receive and conduct electrochemical impulses to and from body parts
• Irritability
• Conductivity
Composed of neurons and nerve support cells
• Support cells called neuroglia insulate, protect, and support neurons
159
Tissue repair (wound healing) occurs in two ways:
1. Regeneration
| 2. Fibrosis
160
Regeneration
Replacement of destroyed tissue by the same kind of cells
161
Fibrosis
Repair by dense (fibrous) connective tissue (scar tissue)
162
Whether regeneration or fibrosis occurs depends on:
* Type of tissue damaged
| * Severity of the injury
163
Events of tissue repair:
• Inflammation- sets the stage
• Granulation- tissue forms
• Regeneration and fibrosis effect permanent repair
*Scab detaches
*Whether scar is visible or invisible depends on severity of wound
164
Inflammation- sets the stage
* Capillaries become very permeable
* Clotting proteins migrate into the area from the bloodstream
* A clot walls off the injured area
165
Granulation- tissue forms
* Growth of new capillaries
* Phagocytes dispose of blood clot and fibroblasts
* Rebuild collagen fibers
166
Tissues that regenerate easily
* Epithelial tissue (skin and mucous membranes)
| * Fibrous connective tissues and bone
167
Tissues that are replaced largely with scar tissue
* Cardiac muscle
| * Nervous tissue within the brain and spinal cord
168
Tissues that regenerate poorly
Skeletal muscle
169
Growth through cell division continues through:
Puberty
170
Connective tissue remains mitotic and forms:
* Repair (scar) tissue
| * With some exceptions, muscle tissue becomes amitotic by the end of puberty
171
Nervous tissue becomes amitotic shortly after:
Birth
172
Injury can severely handicap:
Amitotic tissues
173
The cause of aging is unknown, but a few possible causes have been proposed, such as:
* Chemical and physical insults
| * Genetic programming
174
Neoplasms, both benign and cancerous, represent abnormal cell masses in which:
Normal controls on cell division are not working
175
Hyperplasia (increase in size) of a tissue or organ may occur when:
Tissue is strongly stimulated or irritated
176
Atrophy (decrease in size) of a tissue or organ occurs when:
The organ is no longer stimulated normally
