Physiology and Anatomy Essentials: CELLS & TISSUES

BIOL 111-

CELLS & TISSUES

Dr. Khaled OuanesE-mail: [email protected]

Twitter: @khaled_ouanes

FORM FITS FUNCTION

CELLS AND TISSUES· Cells are the building

blocks of all living beings

· Tissues are group of similar cells from the same origin that carry out a specific function

CELLS

Anatomy of the Cell· Cells are not all the same (Form

fits function here too)

· All cells share general structures

· Cells are organized into 3 main regions Nucleus Cytoplasm Plasma membrane

MAIN REGIONS OF A HUMAN CELL

The Nucleus· Control center of the cell· Contains genetic material

(DNA)

· 3 regions· Nuclear membrane· Nucleolus· Chromatin

NUCLEUS

Nuclear Membrane· Barrier of nucleus· Consists of a double phospholipid (bi-layer) membrane

· Contain nuclear pores allowing material exchange with the rest of the cell

Nucleoli· Nucleus contains one or more nucleoli

· It is a non-membrane bound organelle taking part in synthesis of ribosomes, including processing of rRNA and the assembly of them into ribosome subunits.

Nucleoli· The Nucleus is also involved in several other cellular processes, such as mitosis, stress response and cell cycle regulation.

· After the synthesis step, ribosomes will then migrate to cytoplasm through nuclear pores

Staining of nucleoli in human cell line A-431

Chromatin

· Composed of DNA & proteins

· Scattered throughout the nucleus

· Chromatin condenses to form chromosomes when the cell division starts

ChromatinChromatin and condensed chromosome

structure

Plasma Membrane· Barrier for cell contents· Double phospholipid layer

Hydrophilic heads + Hydrophobic tails

· Other materials in plasma membrane· Protein· Cholesterol· Glycoproteins

Plasma Membrane

Plasma Membrane: Specializations

· Microvilli· Finger-like projections that increase surface area for absorption

· Membrane junctions· Tight junctions· Desmosomes & hemi-desmosomes

· Gap junctions

Plasma Membrane: Specializations

Cytoplasm· Material outside the nucleus and inside the plasma membrane

· Cytosol: Fluid that contains other elements

· Organelles: Metabolic machinery of the cell

· Inclusions: Non-functioning units (Lipids …)

· Ribosomes Made of protein and RNA Sites of protein synthesis Found at two locations Free in the cytoplasm Attached to rough endoplasmic

reticulum

Cytoplasmic Organelles


A ribosome “at work”

· Endoplasmic reticulum (ER): Fluid-filled tubules for carrying substances – 2 types of ER

- Rough Endoplasmic Reticulum: is studded with ribosomes and where building materials of cellular membrane are formed.

- Smooth Endoplasmic Reticulum: Functions in cholesterol synthesis and breakdown, fat metabolism, and detoxification of drugs



Schema of the 2 types of ER


3D of the 2 types of ER

· Golgi apparatus Modifies & packages

proteins Produces several types of

packages· Secretory vesicles· Cell membrane components· Lysosomes



Golgi Apparatus


Golgi Apparatus “at work”

· Mitochondria “Power-houses” of the cell Provide ATP for cellular energy Change shape constantly Carry out reactions using

oxygen break down food



A mitochondrion

· Lysosomes: Contain enzymes that digest non-usable materials within the cell

· Peroxisomes Membranous sacs of oxidase

enzymes Detoxify harmful substances Break down free radicals Replicate by pinching in halves


· Cytoskeleton· Network of protein structures that extend throughout the cytoplasm

· Provides the cell with an internal framework



The cytoskeleton. The actin is stained red and the microtubules, which are composed of the protein tubulin, are

stained green.

· Cytoskeleton3 different types

Microfilaments

Intermediate filaments

Microtubules



The cytoskeleton. This organelle is the ‘skeleton’ of our cells. It maintains cell shape. We couldn’t move without

the cytoskeleton’s contractions of microtubules, microfilaments, and intermediate fibers.

· Centrioles Rod-shaped bodies made of

microtubules Direct formation of mitotic

spindle during cell division Probably involved in other cell

functions that are still not very well known



Centriole

Centrosome

Microtubule

Centrioles

The Cell. The basic unit of structure and function.

Cellular Projections· Not found in all types of cells

· Used for movement: Cilia move materials across the

cell surface Flagellum propels the whole cell

(e.g. sperm cell)

Cellular Projections

Flagella and cilia differ in the way they move. Flagella use an undulating, propeller-like motion to propel a cell. Cilia beat back and forth, perpendicular to the cilium,

bending & sweeping sideways.

Cellular Projections

Flagella and cilia. Movement and structure.

Cell Diversity

Cell Diversity

Cell Diversity

Cell Diversity

Cellular Physiology:Membrane Transport

· Membrane Transport – movement of substance in and out of the cells

· Transport is by 2 basic methods: Passive transport: No energy is

required Active transport: Metabolic

energy required

Solutions and Transport· Solution: homogeneous mixture of 2 or more components Solvent: dissolving medium (e.g.

Water) Solutes: components in smaller

quantities within a solution· Intracellular fluid: nucleoplasm &

cytosol· Interstitial fluid: fluid on the

exterior of the cell (Extracellular fluid)

Selective Permeability· The plasma membrane allows some materials to pass while excluding others

· This permeability includes movement in and out of the cells

Passive Transport Processes· Diffusion· Particles tend to distribute themselves evenly within a solution

· Movement is from high concentration to low concentration, or down a concentration gradient

Passive Transport Processes

Diffusion.

· Types of diffusion· Simple diffusion: Unassisted process. Solutes are lipid-soluble materials or small enough to pass through membrane pores.

· Osmosis – simple diffusion of water: Highly polar water easily crosses the plasma membrane.

· Facilitated diffusion: Substances require a protein carrier for passive transport.


Diffusion through Plasma Membrane

· Filtration: Water and solutes are forced through a membrane by fluid, or hydrostatic pressure. A pressure gradient must exist Solute-containing fluid is pushed

from high pressure area to lower pressure one


Transport of substances that are not able to pass by diffusion because they:

May be too large May be unable to dissolve in the fat of

membranes May have to move against a

concentration gradient

2 common forms of active transport:

Solute pumping & Bulk transport

Active Transport Processes

· Solute pumping Amino acids, some sugars

and ions are transported by solute pumping

ATP energizes protein carriers, & in most cases, moves substances against concentration gradients


Solute Pumping

· Bulk transport· Exocytosis: Moves materials out of the cell. Material is carried in a membranous vesicle.STEPS: Vesicle migrates to plasma

membrane Vesicle combines with plasma

membrane Material is emptied to the outside


Exocytosis

· Bulk transport· Endocytosis: Extracellular substances are engulfed by being enclosed in a membrane vesicle.

· TYPES OF ENDOCYTOSIS:· Phagocytosis: cell eating· Pinocytosis: cell drinking


Endocytosis

Cell Life Cycle

· Cells have 2 major periods· Interphase: Cell grows and carries on metabolic processes

· Cell division: Cell replicates itself 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

Cell Division Steps

· Mitosis: Division of the nucleus. Results in the formation of 2 nuclei.

· Cytokinesis: Division of the cytoplasm. Begins when mitosis is near completion. Results in the formation of 2 new cells.

Stages of Mitosis

· Interphase: No cell division occurs. The cell carries out normal metabolic activity & growth.

· Prophase: First part of cell division. Centromeres migrate to the poles

· Metaphase: Spindle from centromeres are attached to chromosomes that are aligned in the center of the cell

Stages of Mitosis

· Anaphase: Daughter chromosomes are pulled toward the poles. The cell begins to elongate.

· Telophase: Daughter nuclei begin forming. A cleavage furrow (for cell division) begins to form

Stages of Mitosis

Stages of Mitosis

Stages of Mitosis

Protein Synthesis· Gene: DNA segment that carries a

‘blueprint‘ for building one protein

· Proteins have many functions Building materials for cells Act as enzymes (biological catalysts)

· RNA is essential for protein synthesis

Role of RNA

· Transfer RNA (tRNA): Transfers appropriate amino acids to the ribosome for building the protein

· Ribosomal RNA (rRNA): Helps form the ribosomes where proteins are built

· Messanger RNA (mRNA): Carries the instructions for building a protein from the nucleus to the ribosome

Transcription and Translation· Transcription: Transfer of information from DNA’s base sequence to the complimentary base sequence of mRNA.

· Translation: Base sequence of nucleic acid is translated to an amino acid sequence.Remember? Amino acids are the

building blocks of proteins

Proteins Synthesis

TISSUES

Body TissuesCells are specialized for

particular functions

Tissues: Groups of cells with similar origin,

structure and function

Body Tissues4 primary types of tissues:

EpitheliumConnective tissueNervous tissueMuscle

Epithelial Tissues· Found in different areas

Body coverings Body linings Glandular tissue

· Functions Protection Absorption Filtration Secretion

· 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

Epithelium Characteristics

1-Number of cell layers:

· Simple: one layer

· Stratified: more than one layer

Classification of Epithelium

2- Shape of cells:· Squamous: flattened

· Cuboidal: cube-shaped

· Columnar : column-like

Simple Epithelium

• Single layer of flat cells

• Usually forms membranes (Lines body cavities, Lines lungs and capillaries)

Simple squamous

Simple cuboidal

· Single layer of cube-like cells

· Common in glands and their ducts

· Forms walls of kidney tubules

· Covers the ovaries

Simple Epithelium

Simple columnar

· Single layer of tall cells

· Often includes goblet cells, which produce mucus

· Lines digestive tract

Simple Epithelium

Pseudostratified· Single layer, but some cells are shorter than others

· Often looks like a double cell layer

· Sometimes ciliated, such as in the respiratory tract

· May function in absorption or secretion

Simple Epithelium

Stratified squamous

· Cells at the free edge are flattened

· Found as a protective covering where friction is common

· Locations: Skin, Mouth, Esophagus.

Stratified Epithelium

· Stratified cuboidal: Two layers of cuboidal cells.

· Stratified columnar: Surface cells are columnar, cells underneath vary in size and shape.

· Stratified cuboidal and columnar: Rare in human body. Found mainly in ducts of large glands.


Transitional epithelium

· Shape of cells depends upon the amount of stretching

· Lines organs of the urinary system


Gland: one or more cells that secretes a particular product

· 2 major gland types: Endocrine gland: Ductless,

Secretions are hormones. Exocrine gland: Empty through

ducts to the epithelial surface. Include sweat & oil glands.

Glandular Epithelium

· Found everywhere in the body· Includes the most abundant

and widely distributed tissues· Functions:

Binds body tissues together Supports the body Provides protection

Connective Tissue

· Variations in blood supply Some tissue types are well

vascularized Some have poor blood supply or

are avascular

· Extracellular matrix: Non-living material that surrounds living cells

Connective Tissue Characteristics

· 2 main elements:· Ground substance: mostly water along with adhesion proteins and polysaccharide molecules

· Fibers: Produced by the cells 3 types• Collagen fibers• Elastic fibers• Reticular fibers

Extracellular Matrix

Composed of:· Bone cells in lacunae (cavities)

· Hard matrix of calcium salts

· Large numbers of collagen fibers

Connective Tissue TypesBone (osseous tissue):

Used to protect and support the body.

Hyaline cartilage: Most common cartilage. The entire fetal skeleton is hyaline cartilage.

· Composed of: Abundant collagen

fibers Rubbery matrix

Connective Tissue Types

Elastic cartilage· Provides elasticity· Example: supports the external ear


Fibrocartilage· Highly compressible

· Example: forms cushion-like discs between vertebrae


· Main matrix element is collagen fibers

· Cells are fibroblasts

Examples:· Tendon – attach muscle to bone

· Ligaments – attach bone to bone

Connective Tissue TypesDense connective tissue

· Most widely distributed connective tissue

· Soft, pliable tissue· Contains all fiber types

· Can soak up excess fluid

Connective Tissue TypesAreolar connective tissue

Adipose tissue (Fat)Matrix is an areolar tissue in which fat globules predominate. Many cells contain large lipid deposits.

· Functions: Insulates the body Protects some organs Serves as a site of

fuel storage


· Delicate network of interwoven fibers

· Forms stroma (internal supporting network) of lymphoid organs Lymph nodes Spleen Bone marrow

Connective Tissue TypesReticular connective tissue

Blood· Blood cells surrounded by fluid matrix

· Fibers are visible during clotting

· Functions as the transport vehicle for materials


Function is to produce movement· 3 types

Skeletal muscle Cardiac muscle Smooth muscle

Muscle Tissue

Skeletal muscle· Can be controlled voluntarily

· Cells attach to connective tissue

· Cells are striated· Cells have more than one nucleus

Muscle Tissue Types

Cardiac muscle· Found only in the heart

· Function is to pump blood (involuntary)

· Cells attached to other cardiac muscle cells at intercalated disks

· Cells are striated· One nucleus per cell

Muscle Tissue Types

Smooth muscle· Involuntary muscle· Surrounds hollow organs

· Attached to other smooth muscle cells

· No visible striations· One nucleus per cell

Muscle Tissue Types

· Neurons and nerve support cells

· Function is to send impulses to other areas of the body· Irritability· Conductivity

Nervous Tissue

· Regeneration: Replacement of destroyed tissue by the same kind of cells

· Fibrosis: Repair by dense fibrous connective tissue (scar tissue)

· Determination of method Type of tissue damaged Severity of the injury

Tissue Repair

· Capillaries become very permeableIntroduce clotting proteins & Wall off injured area

· Formation of granulation tissue· Regeneration of surface

epithelium

Events in Tissue Repair

· Tissues that regenerate easily: Epithelial tissue Fibrous connective tissue and bone

· Tissues that regenerate poorly: Skeletal muscle

· Tissues that are replaced largely with scar tissue: Cardiac muscle Nervous tissue within the brain and spinal

cord

Regeneration of Tissues

· Epithelial tissue arises from all 3 primary germ layers

· Muscle & connective tissue arise from the mesoderm

· Nervous tissue arises from the ectoderm

· With old age there is a decrease in mass and viability in most tissues

Development aspects of Tissues

BIOL 111-

CELLS & TISSUES

Dr. Khaled OuanesE-mail: [email protected]

Twitter: @khaled_ouanes

Health & Medicine

Physiology and Anatomy Essentials: CELLS & TISSUES