Cell and Tissues
 Cells
are the smallest living subunits of a
multicellular organism such as a human being
 Cells are the building blocks and functional units
of all living things.
 Carry out all chemical activities needed to sustain
life.
 Tissues are groups of cells that are similar in
structure and function.
 Metabolize
 Digest
foods
 Get rid of wastes
 Reproduce
 Grow
 Move
 Respond to a stimulus (irritability)
 Cells
are not all the same but has a
general structures and is formed of three
main regions:



Nucleus
(RBCs are exception)
Cytoplasm
Plasma membrane
I-The Nucleus
 Control center of the
cell, contains genetic
material (DNA), RNA,
& protein.
 46 chromosomes
 Three regions:
a-Nuclear Membrane
 Consists of a double
phospholipid
membrane
 Contain nuclear pores
that allow for
exchange of materials
with the rest of the
cell.
Figure 3.1b
b- Nucleoli
 Nucleus contains one or more nucleoli.
 Sites of ribosome production
 Ribosomes then migrate to the cytoplasm through
nuclear pores

Ribosomes are the site for protein systhesis
c-Chromatin
 Composed of DNA and protein
 Scattered throughout the nucleus
 Chromatin condenses to form chromosomes when the
cell divides.
 II-Plasma
Membrane :phospholipids, cholesterol (decreases
the fluidity of the membrane), and proteins (channels,
transporters, receptors).
 Barrier
for cell contents
 Double phospholipid layer (permit lipid-soluble materials to
easily enter or leave the cell by diffusion through the cell membrane
III-Cytoplasm
 watery solution of
minerals, gases,
organic molecules,
and cell organelles
that is found
between the cell
membrane and the
nucleus.
-Cytosol ,fluid that
suspends other
elements.
-Organelles ,metabolic
machinery of the
cell.
-Inclusions ,nonfunctioning units.
Cytoplasmic Organelles: the main organelles are:
1-Ribosomes:sites of protein synthesis
2-Endoplasmic reticulum (ER):fluid-filled tubules for
carrying substances. It has two types: rough &
smooth
3-Golgi apparatus: modifies and packages proteins &
carbohydrates.
4-Lysosomes:contain enzymes that digest non-usable
materials within the cell.
5-Mitochondria:“powerhouses” of the cell. mitochondria
are he site of ATP (and hence energy) production
 6-Centrioles:rod-shaped bodies made of
microtubules. Direct the formation of mitotic spindle
during cell division. Their function is to organize the
spindle fibers during cell division
Cellular Physiology: Membrane Transport
 Membrane Transport is movement of substance into
and out of the cell
 The plasma membrane allows some materials to pass
while excluding others
 Transport is by two basic methods


Passive transport :No energy is required
Active transport: Energy is needed and must be provided by the
cell
Passive (Physical) Processes
• Require no cellular energy
and include:
• Simple diffusion
• Facilitated diffusion
• Osmosis
• Filtration
Active (Physiological) Processes
• Require cellular energy and include:
• Active transport
• Endocytosis
• Exocytosis
• Transcytosis
14
Passive Transport Processes
1-Diffusion
 Particles tend to distribute themselves evenly within a
solution
 Movement is from high concentration to low one.
 Ex: Gas exchange
 Types of diffusion
-Simple diffusion :solutes are lipid-soluble
materials or small enough to pass through
membrane pores.
-Osmosis :simple diffusion of water
-Facilitated diffusion: Substances require
a protein carrier for passive transport.
Figure 3.9
• Movement of substances from regions of higher concentration to regions of
lower concentration
• Oxygen, carbon dioxide and lipid-soluble substances
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Solute molule
ater moule
A
B
(1)
A
B
A
B
(2)
Time
(3)
16
• Diffusion across a membrane with the help of a channel or carrier molecule
• Glucose and amino acids (needs carrier enzymes)
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Region of higher
concentration
Transported
substance
Region of lower
concentration
Protein carrier
molecule
Cell
membrane
17
Diffusion through the Plasma Membrane
2-Filtration
Water and solutes are forced from a high pressure
area to a lower pressure area ,a pressure gradient
Figure 3.10
must exist.
• Movement of water through a selectively permeable membrane
from regions of higher concentration to regions of lower
concentration
• Water will naturally tend to move to an area
where there is more dissolved material, such as salt or
sugar.
The process of osmosis also takes place in the
kidneys, which reabsorb large amounts of water (many
gallons each day) to prevent its loss in urines
A
A
B
B
(1)
(2)
Time
19
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Osmotic Pressure – ability of osmosis to generate
enough pressure to move a volume of water
• Osmotic pressure increases as the concentration
of nonpermeable solutes increases
• Isotonic – same osmotic pressure
• Hypertonic – higher osmotic pressure
(water loss) ???
• Hypotonic – lower osmotic pressure
(water gain) ???
(a)
(b)
(c)
© David M. Phillips/Visuals Unlimited
20
Active Transport Processes
Transport substances that are unable to pass by diffusion.
-They may be too large
-They may not be able to dissolve in the fat core of the
plasma membrane
-They may have to move against a concentration gradient
 requires the energy of ATP to move
molecules from an area of lesser concentration to an
area of greater concentration.
• Carrier molecules transport substances across a membrane from regions of
lower concentration to regions of higher concentration
• Sugars, amino acids, sodium ions, potassium ions, etc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Carrier protein
Binding site
Cell membrane
Region of higher
concentration
Region of lower
concentration
Phospholipid
molecules
Transported
particle
(a)
Carrier protein
with altered shape
Cellular
energy
(b)
22
1-Solute pumping
 Amino acids, some sugars and ions are
transported by solute pumps.
 ATP energizes protein carriers, and in most
cases, moves substances against
concentration gradients
 The best example is Sodium-Potassium
pump
 Nerve
and muscle cells constantly produce
ATP to keep their sodium pumps (and similar
potassium pumps) working and prevent
spontaneous
impulses.
 Another example of active transport is the
absorption.
 The cells use ATP to absorb these nutrients
from digested food, even when their
intracellular concentration becomes greater
than their extracellular concentration. n of
glucose
• Active transport mechanism
• Creates balance by “pumping” three (3) sodium (Na+) OUT and two (2)
potassium (K+) INTO the cell
• 3:2 ratio
25
Movement of water and dissolved substances from an area of higher
pressure to an area of lower pressure (blood pressure).
• Smaller molecules are forced through porous membranes
• Hydrostatic pressure important in the body
• Molecules leaving blood capillaries
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Capillary wall
Blood
pressure
Tissue fluid
Blood
flow
Larger molecules
Smaller molecules
26
 The
blood pressure in capillaries is higher
than the pressure of the surrounding
tissue fluid. In capillaries throughout the
body, blood pressure forces plasma (water)
and dissolved materials through the capillary
membranes into the surrounding tissue
spaces
 Exocytosis

Material inside the cell migrates to plasma membrane
where a vesicle is formed. It is emptied to the outside.
 Endocytosis

Extracellular substances are engulfed by being
enclosed in a membranous vesicle.
Types of endocytosis


Phagocytosis – cell eating
Pinocytosis – cell drinking
• Cell engulfs a substance by forming a vesicle around the substance
• Three types:
• Pinocytosis – substance is mostly water
• Phagocytosis – substance is a solid
• Receptor-mediated endocytosis – requires the substance to bind to
a membrane-bound receptor
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Cell
membrane
Nucleus Nucleolus
Vesicle
29
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Cell
Particle
membrane
Phagocytized
particle
Vesicle
Nucleus Nucleolus
Receptor-ligand
combination
Molecules
outside cell
Vesicle
Receptor
protein
Cell
membrane
Cell
membrane
indenting
Cytoplasm
(a)
(b)
(c)
(d)30
•
•
•
•
Reverse of endocytosis
Substances in a vesicle fuse with cell membrane
Contents released outside the cell
Release of neurotransmitters from nerve cells
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Endoplasmic
reticulum
Golgi
apparatus
Nucleus
31
• Endocytosis followed by exocytosis
• Transports a substance rapidly through a cell
• HIV crossing a cell layer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
HIV-infected
white blood cells
Anal or
vaginal canal
Viruses bud
HIV
Receptor-mediated endocytosis
Lining of anus
or vagina
(epithelial cells)
Cell
membrane
Exocytosis
Receptor-mediated
endocytosis
Virus infects
white blood cells on
other side of lining
32
Osmosis
Facilitated Diffusion
Active transport
Filtration
Phagocytosis
Pinocytosis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Series of changes a cell undergoes
from the time it forms until the
time it divide
• Stages:
• Interphase
• Mitosis
• Cytokinesis
G2 phase
S phase:
genetic
material
replicates
G1 phase
cell growth
Proceed
to division
Remain
specialized
Restriction
checkpoint
Apoptosis
34
Cytokinesis
Cell Life Cycle
 Cells have two major periods

Interphase



Cell grows but no cell division.
Cell carries on metabolic processes.
Cell division


Cell replicates itself.
Function is to produce more cells for growth and repair processes.
DNA Replication
 Genetic
material
duplicated and readies a
cell for division into two
cells
 Occurs toward the end of
interphase
 DNA uncoils and each side
serves
as a template.
Figure 3.14
 Cell
division is the process by which a cell
reproduces itself.
 There are two types of cell division, mitosis
and meiosis.
 Although both types involve cell
reproduction, their purposes are very
different.
Events of Cell Division
 Mitosis
In mitosis, one cell with the diploid number of
chromosomes (46 for people) divides into two
identical cells, each with the diploid number of
chromosome
 The stages of mitosis are prophase, metaphase,
anaphase, and telophase.
 Division of the nucleus
 Results in the formation of two daughter nuclei
 Cytokinesis
 Division of the cytoplasm
 Begins when mitosis is near completion
 Results in the formation of two daughter cells
Figure 3.15
 Meiosis
is a more complex process of cell
division that results in the formation of
gametes.
 In meiosis, one cell with the diploid number
of chromo cells, divides twice to form four
cells each with the haploid number (half the
usual number) of chromosomes.
 Body
Tissues
 Tissues
are groups of cells with similar structure and
function.
 Four primary tissue types
-Epithelium
-Nervous tissue
 Epithelial
- Connective tissue
- Muscle Tissue
Tissues,found in different areas:
Body coverings
Body linings
Glands
 Functions:
Protection
Absorption
Filtration
Secretion
 are
found on surfaces as either coverings
(outer surfaces) or linings (inner surfaces).
Epithelium Characteristics
Cells fit closely together
 Tissue layer always has one free
surface
 The lower surface is bound by a
basement membrane
 Avascular (have no blood supply)
 Regenerate easily if well nourished
Classification of Epithelium
 According to Number of cell layers
 Simple – one layer
 Stratified – more than one layer
(Oral cavity)

Figure 3.17a
 According




to the Shape of cells
Squamous – flattened (alveoli)
Cuboidal – cube-shaped (thyroid
gland)
Columnar – column-like (stomach
lining); ciliated (trachea)
Pseudostratified
Figure 3.17b
Glandular Epithelium
– one or more cells that secretes a particular
product.
 Three major gland types:
 Endocrine gland = Ductless
 Secretions are called hormones
 Exocrine gland
 Empty through ducts to the epithelial surface
 Include sweat and oil glands, saliva
*Mixed glands: both endo and exocrine glands as
pancreas , ovaries and testes.
 Gland
Connective Tissue
Found everywhere in the body
 The most abundant and widely distributed tissues
 Functions
 Binds body tissues together
 Supports the body
 Provides protection
 Ability to absorb large amount of water (Water reservoir).
Connective Tissue shows variations in blood supply
 Most conn. tissues are well vascularized.
 Tendons and Ligaments have a poor supply.
 Cartillages are avascular

Connective Tissues are made of :
-Different types of cells.
-Non-living substance that surrounds living cells.
-Different types of fibers(collagen,elastin,reticular).
Types of connective tissue
 Conn. T. differ in their fibers present in the matrix
 From most rigid to softest,C.T. major classes are:
-bone
- cartilage
- dense c.t. as tendon,ligament & dermis of skin.
- loose c.t.as areolar,adipose and reticular.
-blood
Fibroblasts
Bone
Cartilage
Muscle Tissue
Muscle is very important, specialized for contraction. It
provides:





movement
maintains posture
supports soft tissue
guards orifices
maintains body temperature
3 Kinds of Muscle CELLs
Skeletal muscle
Cardiac muscle
Smooth muscle
 consists
of nerve cells called neurons
and some specialized cells found only in the
nervous system
 The nervous system has two divisions:
thecentral nervous system (CNS) and
the peripheral nervous system (PNS).
 Neurons are capable of generating and
transmitting electrochemical impulses.
Neural Tissue
 Sends messages throughout the body by
conducting electrical impulses
 The brain and spinal cord are control centers
 The neuron is the basic unit
Tissue Repair (wound healing)
 Healing may be by:
1--regeneration(injured tissues are replaced by the same
type of cells
2- -Fibrosis (the wound is repaired by scar tissue )
3- or both
 Epith.& c.t. regenerate well.
 Mature cardiac muscle & nervous tissue are repaired by
fibrosis.
Developmental aspects
 Growth through cell division continues through
puberty.
 Cells exposed to friction replace lost cells throughout
life(skin , GI tract &bone marrow).
 Conn. T. remains mitotic& forms repair (scar) tissue
 Muscle t. becomes amitotic by the end of puberty.
 Nervous t.become amitotic shortly after birth