Cells and tissues

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Dee Unglaub Silverthorn, Ph.D.
HUMAN PHYSIOLOGY
PowerPoint®
Lecture Slide Presentation by
Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University
AN INTEGRATED APPROACH
T H I R D E D I T I O N
Chapter 3
Cells and Tissues

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About this Chapter
• Cell structure and types
• Cell differentiation
• Compartmentalization
• Mechanical properties and cell functions
• Cell junctions
• Tissue types and characteristics

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Overview: Cells to Organ Systems
Figure 3-4d, e: Anatomy Summary: Levels of Organization—System to Cell

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• Cytosol
• Organelles
• Inclusion
• Dissolved
• Insoluble
Cell Cytoplasm
Figure 3-3: A map for the study of cell structure

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• Ribosomes
• Free
• Fixed
• Protein synthesis
• Vaults:
• large nucleoprotein particles (mostly protein) which have
39 fold symmetery.
• 3X the size of ribosomes and are present in many types of
eukaryotic cells, Highly conserved among eukaryotes.
• Precise function unknown but they may play a role in
protein synthesis; in transport of mRNA to cytoplasm, and
may play a role in fighting pathogens
Nonmenbranous Organelles

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Nonmenbranous Organelles
Figure 3-6: Ribosomes are nonmembranous organelles
composed of RNA and protein

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• Internal lumen and membranes for protected
reactions
• Mitochondria: Generates cell energy (ATP) , have
DNA
Membranous Organelles: Create cell compartments
Figure 3-9: Mitochondria

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• Smooth ER: Lipid synthesis & conversion
• Rough ER: Ribosomes, protein assembly &
transport vesicles
Endoplasmic Reticulum (ER) ad Ribosomes
Figure 3-10: The endoplasmic reticulum

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• Protein packaging
• Secretory vesicles
• Secreted to E C F
Golgi Apparatus

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Golgi Apparatus
Figure 3-11: The Golgi apparatus

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• Lysosomes
• Enzymes
• Intracellular
digestion
• Peroxisomes
• Hydrogen
peroxide
• Detoxification
• Fatty acid
degradation
Cytoplasmic Vesicles
Figure 3-12: Lysosomes and peroxisomes

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• Nuclear envelope
• Nuclear pore complex
• Chromatin
• DNA form genes
• Nucleoli
• DNA concentrations
• Control rRNA synthesis
Nucleus

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Nucleus
Figure 3-13: The nucleus

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Overview: Cells to Organ Systems
Figure 3-4a-c: Anatomy Summary: Levels of Organization—System to Cell

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Cell Membrane
Figure 3-5: The cell membrane

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The importance of selectively permeable membranes
•Membranes are physical barriers of
cells and subcellular compartments
controlling material exchange
between the internal environment
and the extracellular environment
•A membrane is essentially a
hydrophobic permeability barrier
consisting of phospholipids,
glycolipids, and membrane proteins
•Membranes contain amphipathic
molecules such as phosphatidyl
ethanolamine, an example of
phosphoglycerides, the major class
of membrane phospholipids in most
cells.
Polar
head
Nonpolar
tail

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Cell Junctions:
• Gap Junctions: Simplest Cell-Cell Junction. Can
open and close. Present in many tissues. Proteins
associated with: Connexins
• Tight Junctions: Cell-Cell Junction in Epithelial
tissue that does not allow much movement of
material between cells. Proteins associated with:
Claudins and Occludins. Blood Brain Barrier
• Anchoring Junctions: Attach cells to each other
(cell-cell anchoring junction) or to the ECM (cell-
matrix anchoring junction). Proteins associated
with: Cadherins and integrins

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Junctions
Figure 3-14: Types of cell junctions

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Key Junction Proteins:
Connexin, cadherins, occludin & integrins
Figure 3-15: A map of cell junctions

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• Cell to cell
• Gap junctions: between heart muscle cells
• Tight junctions: blood brain barrier
• Anchoring junctions:
• Desmosomes- attach to intermediate
filaments of cytoskeleton
• Adherens Junctions- link actin in adjacent
cells
Junctions

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Junctions
• Cell to matrix: Anchoring Junctions
• Focal Adhesions- junction between
intracellular actin and matrix proteins
• Hemidesmosomes- strong junction that ties a
cell to the matrix proteins

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Types of Anchoring Junctions
• Cell- Cell Anchoring Junctions:
Adherens Junction- links actin in adjacent cells
and
Desmosomes- attach to intermediate filaments of
cytoskeleton
• Cell-Matrix Anchoring Junctions:
--Focal adhesions- bind intracellular actin to
different matrix proteins such as fibronectin
--Hemidesmosomes- strong junctions
that anchor intermediate fibers of the
cytoskeleton to matrix proteins such as laminin

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Cytoskeleton
• Three Dimensional Scaffold of Actin,
Intermediate Filaments and Microtubules
• Responsible for Cell Shape, internal organization,
movement, intracellular transport and assembly
of cells into tissue

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Cytoskeleton
Figure 3-7: The cytoskeleton and cytoplasmic protein fibers

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• Strength
• Support
• Shape
• Transport
• Cell to cell links
Cytoskeleton

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Cytoskeleton
• Microfilaments: Composed of Actin
• Intermediate Filaments: Composed of Myosin,
Keratin, Neurofilament and other proteins
• Microtubules: Largest cytoplasmic protein fibers.
Creates centrioles, cilia and flagella. Composed of
tubulin (a globular protein)
• Motor Proteins: Composed of multiple protein
chains that bind to the cytoskeleton. Proteins
involved include myosin, Kinesins and Dyneins

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The Centrosome
• The centrosome is located in the cytoplasm usually close to
the nucleus.
• It consists of two centrioles — oriented at right angles to
each other — embedded in a mass of amorphous material
containing more than 100 different proteins.
• It is duplicated during S phase of the cell cycle.
• Just before mitosis, the two centrosomes move apart until
they are on opposite sides of the nucleus.
• As mitosis proceeds, microtubules grow out from each
centrosome with their plus ends growing toward the
metaphase plate. These clusters of microtubules are called
spindle fibers.

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• Centrosomes are the microtubule organizing centers
• Centrioles: bundles of microtubules
• Centrioles are built from a cylindrical bundle of 27 microtubules
arranged in nine triplets.
Centrosomes and Centrioles
Figure 3-8a,c: Centrioles, cilia, and flagella

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• Motor proteins
• 2:9 microtubule pattern
• Cilia move fluids
• Flagella move sperm cell
Cilia and Flagella
Figure 3-8c, d: Centrioles, cilia, and flagella

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Extracellular Matrix
• Extracellular material that is synthesized and
secreted by the cells of a tissue.
• Composed of Proteoglycans (glycoproteins or
proteins covalently bound to polysaccharide
chains) and Insoluble protein fibers such as
collagen, fibronectin, laminin, fibrillin and
elastin.
• It provides strength and helps anchor cells to the
Matrix
• Attachments between the ECM and proteins in
cell membrane or cytoskeleton are one means of
communication between cell and environment

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Proteoglycans
• Proteoglycans are glycoproteins that are heavily glycosylated. The
basic proteoglycan unit consists of a "core protein" with one or more
covalently attached glycosaminoglycan (GAG) chain(s).
• The point of attachment is a Ser residue to which the glycosaminoglycan
is joined through a tetrasaccharide bridge (For example: chondroitin
sulfate-GlcA-Gal-Gal-Xyl-PROTEIN).
• The Ser residue is generally in the sequence -Ser-Gly-X-Gly- (where X
can be any amino acid residue), although not every protein with this
sequence has an attached glycosaminoglycan.
• The chains are long, linear carbohydrate polymers that are negatively
charged under physiological conditions, due to the occurrence of sulfate
and uronic acid groups. Proteoglycans occur in the connective tissue.

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Cell Membrane Proteins
• Cell Adhesion Molecules (CAMS)- Membrane
spanning proteins responsible for cell junctions
and transient cell adhesions. Include Claudins,
Occludins, Cadherins, Integrins and Selectins
• Cell-Cell and Cell-Matrix Adhesions are mediated
by these Cell Adhesion Molecules
• Growing nerve cells move along ECM with help of
nerve cell adhesion molecules (NCAM’s)
• Cell Adhesions are not permanent so the bond
between CAM’s may be weak

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Cell Adhesion Molecules (CAM’s)
• Attachments between ECM and Cell Membrane
Proteins or Cytoskeleton are a means of
communication between a cell and its external
environment

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• Tissue defined: A collection of cells usually held
together by cell junctions that works together to
achieve a common purpose
• Amount of Extracellular Matrix in a tissue is
highly variable
• Tissue types
• Epithelial
• Connective
• Muscle
• Nervous
Primary Tissue Types

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Epithelial Tissue
• Protects the internal environment of the body and
regulates exchange of materials between the
internal and external environment
• Five Functional Types: Exchange, Transporting,
Ciliated, Protective and Secretory

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Epithelial Tissues
Figure 3-17: Distribution of epithelia in the body

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• Leaky junctions
• Rapid transport
• Oxygen
• Carbon dioxide
• Ions & fluids
• Capillaries
• Lung alveoli
Exchange Epithelial Tissues
Figure 3-18a: Movement of substances across tight and leaky epithelia

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• Transport epithelium
• Intestinal microvili
• Tight junctions
• Ciliated epithelium
• Trachea
• Sweep mucous out
• Protective epithelium
• Skin
• Multiple cell layers
• Prevent exchange
More Epithelia
Figure 3-18b: Movement of substances across tight
and leaky epithelia

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• Ciliated epithelium
• Trachea
• Sweep mucous out
• Protective epithelium
• Skin
• Multiple cell layers
• Prevent exchange
More Epithelia
Figure 3-19a: Ciliated epithelia

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• Exocrine tissues
• Mucous glands- goblet cells
• Sweat glands
• Secreted externally
• Endocrine tissues
• Hormones
• Secreted to ECF & blood
Secretory Epithelia

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Secretory Epithelia
Figure 3-20: Goblet cells

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Connective Tissue
• Provides structural support and sometimes
physical barriers that along with specialized cells
helps defend the body from foreign invaders.
• The distinguishing characteristic is an
extracellular matrix with widely scattered cells
that secrete and modify the matrix. Blood,
cartilage, bone, support tissues for skin and
organs
• ECM of Connective Tissue is a ground substance
of proteoglycans and water in which insoluble
protein fibers are arranged

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Connective Tissue
• Loose Connective Tissue: Underlies skin and
provides support for small glands
• Dense Connective Tissue: Provides strength and
flexibility- ligaments, tendons and muscle sheaths

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• Matrix
• Fibers & their functions
• Fibroblast cells
• Collagen
• Elastin
• Fibrillin
• Fibronectin
Connective Tissues (CT)

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Connective Tissues (CT)
Figure 3-22: Cells and fibers of connective tissue

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• Dense
connective
tissue
• Tendons &
ligaments
• Collagen
dominates
More Connective Tissues
Figure 3–23: Tendons and ligaments

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More Connective Tissues
• Adipose connective tissue
• Adipocytes
• Fat vacuoles
• Blood
• Plasma matrix
• Free blood cells

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Supporting Connective Tissues
Figure 3-25: Map of the components of connective tissue

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Muscle and Nerve
• Have very little Extracellular Matrix
• Muscle has the ability to contract and produce
force and movement
• Neural tissue has two types:
Neurons- Carry information in the form of
chemical and electrical signals from one part of
the body to another
Glial cells or Neuroglia- Provide support for
neurons.

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• Contractile
• Force
• Movement
• Excitable- they
conduct signals
• Types
• Cardiac
• Smooth
• Skeletal
Muscle Tissues
Figure 12-1: Three types of muscles

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• Neurons send signals
• Excitable
• Electrical
• Chemical
• Glial cells support
Nervous Tissues
Figure 8-2: Model neuron

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• Necrosis
• Damaged cells die
• Disrupt/kill neighbors
• Apoptosis
• Normal cell replacement
• Programmed cell death
• Does not damage neighbors
• Stem cells
• Role in cell replacement
• Research uses and potential
Cell Life, Death, and Replacement

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Apoptosis
• Apoptosis is a naturally occurring process by which a cell is
directed to Programmed Cell Death. Apoptosis is based on a
genetic program that is an indispensable part of the
development and function of an organism. In this process,
cells that are no longer needed or that will be detrimental to
an organism or tissue are disposed of in a neat and orderly
manner; this prevents the development of an inflammatory
response, which is often associated with Necrotic cell death.
There are at least two broad pathways that lead to
Apoptosis, an "Extrinsic" and an "Intrinsic" Pathway. In
both pathways, signaling results in the activation of a family
of Cys (Cysteine) Proteases, named Caspases that act in a
proteolytic cascade to dismantle and remove the dying cell.

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• Organ defined: A group of tissues that carries out
related functions
• Skin
• Epidermal tissue
• Multiple cell layers
• Keritin: hardened
• Desmosomes: junctions holding cells
together
Organs:
Focus on the Skin, the Body’s Largest Organ

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Functions of skin
• Protection
• Cushions and insulates and is waterproof
• Protects from chemicals, heat, cold, bacteria
• Screens UV
• Synthesizes vitamin D with UV
• Regulates body heat
• Prevents unnecessary water loss
• Sensory reception (nerve endings)

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Remember…
• Four basic types of tissue
• Epithelium – epidermis
• Connective tissue - dermis
• Muscle tissue
• Nervous tissue

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Epidermis
• Keratinized stratified squamous epithelium
• Four types of cells
• Keratinocytes – deepest, produce keratin (tough fibrous protein)
• Melanocytes - make dark skin pigment melanin
• Merkel cells – associated with sensory nerve endings
• Langerhans cells – macrophage-like dendritic cells
• Layers (from deep to superficial)
• Stratum basale or germinativum – single row of cells attached to
dermis; youngest cells
• Stratum spinosum – spinyness is artifactual; tonofilaments
(bundles of protein) resist tension
• Stratum granulosum – layers of flattened keratinocytes producing
keratin (hair and nails made of it also)
• Stratum lucidum (only on palms and soles)
• Stratum corneum – horny layer (cells dead, many layers thick)

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Epithelium: layers (on left) and cell types (on right)

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Dermis
• Strong, flexible connective tissue: your “hide”
• Cells: fibroblasts, macrophages, mast cells,
WBCs
• Fiber types: collagen, elastic, reticular
• Rich supply of nerves and vessels
• Critical role in temperature regulation (the
vessels)
• Two layers (see next slides)
• Papillary – areolar connective tissue; includes dermal
papillae
• Reticular – “reticulum” (network) of collagen and
reticular fibers

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*Dermis layers
*
*
*Dermal papillae

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Hypodermis
• “Hypodermis” (Gk) = below the dermis
• “Subcutaneous” (Latin) = below the skin
• Also called “superficial fascia”
“fascia” (Latin) =band; in anatomy: sheet of connective
tissue
• Fatty tissue which stores fat and anchors skin
(areolar tissue and adipose cells)
• Different patterns of accumulation
(male/female)

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Burns
• First degree- Epidermis appears red (erythema). Dry texture. Painful.
1wk or less to heal
• Second degree (superficial partial thickness) Extends into superficial
(papillary) dermis- Appears red with clear blisters. Blanches with
pressure. Moist texture. Painful . 2-3wks to heal. Complications-Local
infection/cellulitis
• Second degree (deep partial thickness) Extends into deep (reticular)
dermis. Appears red-and-white with bloody blisters. Less blanching.
Moist texture. Painful. Weeks to heal - may progress to third degree
burn. Can cause scarring, contractures (may require excision and skin
grafting)
• Third degree (full thickness). Extends through entire dermis. Stiff and
white/brown appearance. Dry, leathery texture. Painless. Requires
excision. Complications- Scarring, contractures, amputation
• Fourth degree Extends through skin, subcutaneous tissue and into
underlying muscle and bone. Appears black and charred. Dry texture.
Painless. Requires excision. Complications: possible gangrene.

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• Dermal tissues
• Loose CT
• Fibers & muscles
• Hair, sweat glands
• Sebaceous glands
• Hypodermal tissues
• Blood vessels
• Nerves
• Adipose & loose CT
More on Skin

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• Cell components & functions:
• Membrane, cytoplasm, cytoskeleton,
ribosomes, centrosome, mitochondria, smooth
& rough ER, golgi apparatus, lysosomes ,
peroxisomes and the nucleus
• Cell junctions and matrix
• Primary tissues types & characteristics:
• epithelial, connective, muscle, and nervous
• Cell death & replacement
• Skin as an example of an organ
Summary