cells and tissues

Dee Unglaub Silverthorn, Ph.D.

HUMAN PHYSIOLOGY

PowerPoint® Lecture Slide Presentation byDr. 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 3Cells and Tissues

About this Chapter

• Cell structure and types

• Cell differentiation

• Compartmentalization

• Mechanical properties and cell functions

• Cell junctions

• Tissue types and characteristics

Overview: Cells to Organ Systems

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

• Cytosol

• Organelles

• Inclusion

• Dissolved

• Insoluble

Cell Cytoplasm

Figure 3-3: A map for the study of cell structure

• 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

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

• Internal lumen and membranes for protected reactions

• Mitochondria: Generates cell energy (ATP) , have DNA

Membranous Organelles: Create cell compartments

Figure 3-9: Mitochondria

• Smooth ER: Lipid synthesis & conversion

• Rough ER: Ribosomes, protein assembly & transport vesicles

Endoplasmic Reticulum (ER) ad Ribosomes

Figure 3-10: The endoplasmic reticulum

• Protein packaging

• Secretory vesicles

• Secreted to E C F

Golgi Apparatus

Figure 3-11: The Golgi apparatus

• Lysosomes

• Enzymes

• Intracellular digestion

• Peroxisomes

• Hydrogen peroxide

• Detoxification

• Fatty acid degradation

Cytoplasmic Vesicles

Figure 3-12: Lysosomes and peroxisomes

• Nuclear envelope

• Nuclear pore complex

• Chromatin

• DNA form genes

• Nucleoli

• DNA concentrations

• Control rRNA synthesis

Nucleus

Figure 3-13: The nucleus

Overview: Cells to Organ Systems

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

Cell Membrane

Figure 3-5: The cell membrane

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 headNonpolar tail

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

Junctions

Figure 3-14: Types of cell junctions

Key Junction Proteins: Connexin, cadherins, occludin & integrins

Figure 3-15: A map of cell junctions

• 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

• 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

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

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

Cytoskeleton

Figure 3-7: The cytoskeleton and cytoplasmic protein fibers

• Strength

• Support

• Shape

• Transport

• Cell to cell links

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

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.

• 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

• Motor proteins

• 2:9 microtubule pattern

• Cilia move fluids

• Flagella move sperm cell

Cilia and Flagella

Figure 3-8c, d: Centrioles, cilia, and flagella

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

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.

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

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

• 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

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

Epithelial Tissues

Figure 3-17: Distribution of epithelia in the body

• 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

• 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

• Ciliated epithelium

• Trachea

• Sweep mucous out

• Protective epithelium

• Skin

• Multiple cell layers

• Prevent exchange

More Epithelia

Figure 3-19a: Ciliated epithelia

• Exocrine tissues

• Mucous glands- goblet cells

• Sweat glands

• Secreted externally

• Endocrine tissues

• Hormones

• Secreted to ECF & blood

Secretory Epithelia

Figure 3-20: Goblet cells

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

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

• Matrix

• Fibers & their functions

• Fibroblast cells

• Collagen

• Elastin

• Fibrillin

• Fibronectin

Connective Tissues (CT)

Figure 3-22: Cells and fibers of connective tissue

• Dense connective tissue

• Tendons & ligaments

• Collagen dominates

More Connective Tissues

Figure 3–23: Tendons and ligaments

More Connective Tissues

• Adipose connective tissue

• Adipocytes

• Fat vacuoles

• Blood

• Plasma matrix

• Free blood cells

Supporting Connective Tissues

Figure 3-25: Map of the components of connective tissue

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.

• Contractile

• Force

• Movement

• Excitable- they conduct signals

• Types

• Cardiac

• Smooth

• Skeletal

Muscle Tissues

Figure 12-1: Three types of muscles

• Neurons send signals

• Excitable

• Electrical

• Chemical

• Glial cells support

Nervous Tissues

Figure 8-2: Model neuron

• 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

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.

• 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

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)

Remember…• Four basic types of tissue

• Epithelium – epidermis

• Connective tissue - dermis

• Muscle tissue

• Nervous tissue

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)

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

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

*Dermis layers

*Dermal papillae

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)

• 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.

• Dermal tissues

• Loose CT

• Fibers & muscles

• Hair, sweat glands

• Sebaceous glands

• Hypodermal tissues

• Blood vessels

• Nerves

• Adipose & loose CT

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