Transcript Human Anatomy, First Edition McKinley&O'Loughlin

Human Anatomy,
First Edition
McKinley & O'Loughlin
Chapter 2 :
The Cell: Basic Unit
of Structure and
Function
1
The Cell
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Cells:
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structural and functional units of all living
organisms.
building blocks of the human body.
adult human body contains ~ 75 trillion cells.
Each cell type performs specific functions.
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~200 cell types in humans
 subcategories of most
2-2
Common Characteristics of
Cells
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Perform the general functions necessary to
sustain life:
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Obtain nutrients and other materials from its
surrounding fluids.
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Dispose of wastes products
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Urea (from nitrogen), CO2, metabolic waste
Maintain shape and integrity
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Fuel molecules, O2, building blocks, minerals,etc
Size and shape are related to function
Cell division:
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Mitosis: growth and repair
Meiosis: gamete formation
2-3
Study of Cells
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Cytology: study of cells
Microscopic anatomy
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Individual cells observable by light microscopy
Subcellular structures observable by electron
microscopy.
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TEM
SEM
Unit of measure: micrometer (um)
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RBC: 7-8um
2-4
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Cells
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Parts of a cell
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Cell Membrane (or plasma membrane)
Cytoplasm
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Cytosol
Organelles
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Membranous Organelles
Non-membranous Organelles
Inclusions
Nucleus
2-6
Plasma (Cell)
Membrane
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the outer,
limiting barrier
separates the
internal
contents of the
cell from
external
materials.
2-7
Cytoplasm
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general term for all cellular contents
located between the plasma membrane
and the nucleus.
2-8
Nucleus
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“control center” of the cell
controls protein synthesis
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directs the functional and structural
characteristics of the cell.
2-9
Plasma membrane: composition
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Lipids
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Phospholipids
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Head: hydrophilic
Tail: hydrophobic
Form lipid bilayer
Cholesterol
Glycolipids
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Carbohydrate component
Part of glycocalyx
2-10
11
Plasma membrane: composition
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Protein
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Integral membrane proteins
Peripheral membrane proteins
Some serve as enzymes, ion channels or
receptors
Glycoproteins
2-12
Plasma membrane: functions
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Selectively permeable barrier
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Nutrient in
Waste out
Communication
Intercellular connections
Physical barrier
2-13
Transport Mechanisms
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Passive Transport
Active Transport
Bulk Transport
Solution= solvent (H2O)+ solute
2-14
Passive Transport
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Movement of substances along a
concentration gradient
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[Hi] to [Low]
ATP is not required
Types:
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Simple Diffusion: solutes
Facilitated Diffusion: solutes
Bulk Filtration: solution
Osmosis: solvent
2-15
Facilitated Diffusion
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Requires the participation of specific
transport proteins that help specific
substances or molecules move across
the plasma membrane.
“Carrier-mediated”
2-16
Bulk Filtration
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Involves the diffusion of both solvents
and solutes together across the
selectively permeable membrane.
Pressure gradients
2-17
Osmosis
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Involves the diffusion of a solvent
(H2O), across a selectively permeable
membrane.
Can cause a volume change
2-18
Active Transport
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Movement of a substance across a plasma membrane
against a concentration gradient.
Materials must be moved from an area of low
concentration to an area of high concentration.
 requires cellular energy in the form of ATP
(adenosine triphosphate)
 uses transport proteins (carrier-mediated)
 ATP is continually synthesized by mitochondria
2-19
Ion Pumps
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Active transport processes that move
ions across the membrane are called ion
pumps.
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ion pumps allow a cell to maintain its
internal concentrations of small molecules
or ions
2-20
Bulk Transport - Exocytosis
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Used by cells that secrete
Usually movement of large molecules
Movement out of the cell.
2-21
22
Bulk Transport - Endocytosis
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process by which the cell acquires materials from the
extracellular fluid: (3 Forms)
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Phagocytosis:
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Pinocytosis:
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Cell forms pseudopodia
engulfs a particle
internalize it into a vacuole
incorporation of droplets of extracellular fluid (solution)
Taken into the cell in small vesicles
Receptor-mediated endocytosis:
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receptors in the cell membrane
Bind with specific molecules
Invagination forms around them to create a cytoplasmic vesicle
2-23
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Cytoplasm: cytosol
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Matrix; intracellular material
Different in different cell
Mostly water
2-26
Cytoplasm: Organelles
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Complex, organized structures
Have unique, characteristic shapes.
Each type performs a different function
for the cell.
Are essential for normal cellular
structure and activities.
2-27
Membranous Organelles
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Include:
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Endoplasmic Reticulum
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Rough Endoplasmic Reticulum (RER)
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Ribosomes
Make protein for export
Peroxisomes made here
Smooth Endoplamic Reticulum (SER)
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Lipids and carbohydrates
Detoxification
2-28
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Membranous Organelles
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Peroxisomes
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Vesicles formed from RER
Use oxygen to detoxify
Mediated by specific enzymes
Most abundant in liver
2-31
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Membranous Organelles
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Golgi Apparatus
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Modifies, stores and sorts material from
RER
Receiving region (cis-face)
Shipping region (trans-face)
Produces Lysosomes
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Autophagy: removal of old organelles
Autolysis: destruction of the cell
2-33
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Mitochondria
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Mitochondria are organelles with a
double membrane.
Produce large amounts of ATP.
Are called the “powerhouses” of the
cell.
2-37
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Non-Membranous Organelles
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Not made of a membrane.
Usually made of protein
Include:
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Ribosomes: free and fixed
Cytoskeleton
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Microfilaments
Intermediate fibers
microtubules
Centrosome
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centrioles
2-39
Ribosomes
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Small, dense granules
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Protein
RNA
Site of protein synthesis.
Each ribosome has a small and a large
subunit.
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small subunit is about one-half the size of
the large subunit.
2-40
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The Cytoskeleton
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Made of filamentous proteins
Helps give the cell its shape
Coordinates cellular movements.
Three categories:
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microfilaments
intermediate filaments
microtubules
2-42
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Non-membranous Organelles
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Centrioles and the centrosome
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Centrosome
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Area close to the nucleus
Organization site for microtubules
Centrioles (exist as a pair)
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In the centrosome
Perpendicular to each other
9 sets of microtubule triplets
Important in cell division (spindle)
2-44
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Microvilli, Cilia and Flagella
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Appendages extending from the surface of some
cells.
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Microvilli:
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Cilia:
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short, cytoplasmic extensions
For absorption
usually occur in large numbers
work together to move materials or fluids along the surface of
a cell.
Flagella:
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longer than cilia, and usually occur as single appendages.
Move the cell
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The Nucleus
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Control center of cellular activities.
Usually, it is the largest structure within
the cell
Appears as a single spherical or oval
structure.
2-48
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The Nucleus
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Enclosed by a double membrane called
the nuclear envelope.
The nuclear envelope:
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controls the entry and exit of materials
between the nucleus and the cytoplasm.
2-50
Nucleolus
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The cell nucleus may contain one or
more nucleoli.
Nucleoli:
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are responsible for making the small and
the large subunits of ribosomes.
2-51
Chromatin and DNA
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DNA is the genetic material housed
within the nucleus.
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DNA is a polymer of nucleotides (sugar,
phosphate, nitrogen base)
Is a double helix.
Chromatin:
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Strands of DNA and histone proteins
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Euchromatin: uncoiled; active
Heterochromatin: coiled. inactive
2-52
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Insert Figure 2.18
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Chromosome
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The chromosome is the most organized
level of genetic material.
Each chromosome contains a single,
long molecule of DNA and associated
proteins.
Chromosomes become visible only
when the cell is dividing.
2-55
The Cell Cycle
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The life cycle of the cell is called the cell
cycle.
New cells must be made continuously in
order for an organism to grow and
replace its damaged cells.
2-56
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Mitosis and Meiosis
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There are two types of cell division.
Mitosis: is the cell division process that
takes place in somatic cells.
Meiosis: is the cell division process that
takes place in gonads to produce
gametes.
2-58
Mitosis
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
2-59
The Stages of Mitosis
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Prophase – the first and longest stage of
mitosis
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Early prophase – chromatin threads condense
into chromosomes
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Chromosomes are made up of two threads called
chromatids
Chromatids are held together by the centromere
Centriole pairs separate from one another
The mitotic spindle forms
2-60
The Stages of Mitosis
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Prophase (continued)
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Late prophase – centrioles continue moving
away from each other
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Nuclear membrane fragments
2-61
Early Prophase and Late
Prophase
Figure 2.21
2-62
The Stages of Mitosis
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Metaphase – the second stage of mitosis
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Chromosomes cluster at the middle of the cell
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Centromeres are aligned along the equator
Anaphase – the third and shortest stage of
mitosis
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Centromeres of chromosomes split
2-63
Metaphase and Anaphase
Figure 2.21
2-64
The Stages of Mitosis
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Telophase – begins as chromosomal
movement stops
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Chromosomes at opposite poles of the cell
uncoil
Resume their thread-like extended-chromatin
form
A new nuclear membrane forms
Cytokinesis – completes the division of the
cell into two daughter cells
2-65
Telephase and Cytokinesis
Figure 2.21
2-66
Tumor
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Normal tissue development exhibits a
balance between cell division and cell
death.
If this balance is upset and cells
multiply faster than they die, abnormal
growth results in a new cell mass that is
called a neoplasm, or tumor.
2-67
Cancer
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Benign neoplasms usually grow slowly and are
confined within a connective tissue capsule.
Cells within these tumors dedifferentiate—that is,
they revert to a less specialized state, and cause an
increase in their own vascular supply to support their
growth.
These tumors are usually not lethal, but they have
the potential to become life-threatening if they
compress brain tissue, nerves, blood vessels, or
airways.
2-68
Cancer
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Cancer is the general term used to describe a
group of diseases characterized by various
types of malignant neoplasms.
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unencapsulated
contain cells that dedifferentiate
increase their vascular supply
grow rapidly
spread easily to other organs by way of the blood
or lymph (metastasis)
2-69
Cancer
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Cancer cells lose control of their cell
cycle.
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they divide too frequently and grow out of
control
cancer cells lose contact inhibition
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they overgrow one another and lack the ability
to stop growing and dividing when they crowd
other cells
2-70
Cancer Cells
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Exhibit dedifferentiation and revert to an earlier, less
specialized developmental state.
Produce chemicals that cause local blood vessel
formation resulting in increased blood vessels in the
developing tumor (angiogenesis).
Have the ability to squeeze into any space
(invasiveness) permitting them to leave their place of
origin and travel elsewhere in the body.
Acquire the ability to metastasize—that is, spread to
other organs in the body.
2-71