Cells and Tissues SAP1d. Relate cellular metabolism and transport to homeostasis and

cellular reproduction.

SAP1e. Describe how structure and function are related in terms of cell

and tissue types.

Cells

• Founded by Robert Hooke in the late 1600’s.

• Cells are the building blocks of all living things, animals and plants.

• The human body has trillions of them.

Biochemistry • Cells are made up primarily of four elements—

carbon, oxygen, hydrogen, and nitrogen, plus trace elements.

• The 4 elements make up most of the cell’s structure….which is mostly protein.

• The trace elements are important for certain cell functions.

• Ca—blood clotting, Fe—hemoglobin carries O2 in blood, I—thyroid protein for metabolism, metals, Ca, Na, K, carry an electric charge (electrolytes).

• Na and K—nerve impulses for muscle contraction

• Living cells are 60% water.

• Cells live in interstitial fluid (a dilute salt water solution), which is derived from the blood. All exchanges between cells and blood are made through this fluid.

• Cells vary in size, from 2 micrometers (1/12000 of an inch) to over a meter (the nerve cell that makes your toes wiggle).

• Cells have different shapes, depending on their function.

All cells have 3 main regions:

• 1. Nucleus

A. control center

B. contains DNA—instructions for building proteins.

C. has 3 regions:

1. nuclear envelope—double membrane barrier

2. nucleoli—where ribosomes are assembled

a. ribosomes—where proteins are synthesized

3. chromatin—DNA and protein, when cell is not dividing. Condense to form chromosomes when it is.

Parts of the Cell • 2. The plasma membrane- the phospholipid bi-

layer makes it impermeable to most water soluble molecules.

• Cholesterol makes it fluid. • Plasma Membrane Proteins

– Enzymes – Receptors for hormones – Binding sites for anchoring cells to structures – Protein channels—pores that water and small

molecules can move through. – Carriers—pull things through – Glycoproteins—sugar groups

Plasma Membrane

Specializations of the Plasma Membrane

• 1. Microvilli—tiny hair like projections that increase the surface area of cells, so they can absorb more quickly.

• 2. Membrane Junctions • A. Tight Junctions—bind cells together into leak-proof

sheets so things can’t pass through space between cells. Like a zipper.

• B. Desmosomes—Anchoring junctions that prevent cells subject to mechanical stress (ex. skin cells) from being pulled apart. Like wires.

• C. Gap Junctions—allow communication (heart and embryonic cells). Chemicals can pass through from one cell to another. Neighboring cells connected by connexons.—hollow cylinders.

Parts of the cell

• 3. The Cytoplasm

– A. The cellular material outside the nucleus and inside the plasma membrane.

– B. Consists of 3 parts:

• 1. The cytosol- semi-transparent fluid that suspends the other elements.

• 2. The organelles—metabolic machinery of the cell.

• 3. Inclusions—chemical substances that may or may not be present, depending on the specific cell type. Can be stored nutrients or cell products.

Membrane Transport • Intercellular fluid –inside the cell • Interstitial fluid—outside the cell (contains 1000’s of ingredients,

including amino acids, sugars, fatty acids, vitamins, hormones, neurotransmitters, salts, and waste products.

• To remain healthy, cells must take the substances it needs at specific times and reject the rest. The movement of materials into and out of cells influences the internal concentrations of the molecules. So, you can see that what goes in or out will have a profound effect on the ability of cells to function properly. The ability of cells to move materials in and out efficiently can determine whether they will live or die. How do cells control these movements?

• The plasma membrane is selectively permeable, allowing some substances to pass through while excluding others. (Permeable means porous or penetrable). It is the “gate keeper” of the cell.

Movement of substances through the plasma membrane happens in two ways:

• 1. Passive Transport— no energy input is required from the cell. It just happens (actually the kinetic energy of the particles themselves –bc they have heat--provides the energy).

• A. Diffusion—movement of particles from a higher concentration to a lower concentration until evenly distributed (equilibrium). (Particles will move until they are randomly distributed in space). Nonpolar and lipid soluble move through the phospholipid bilayer. (O2, CO2, fats, urea, alcohol)

1. polar, lipid insoluble substances can diffuse through the protein channels if small enough.

2. the greater the concentration difference, the faster the diffusion.

Example: food coloring in water Watch video clip: https://www.youtube.com/watch?v=6yMPpDeNwqQ

Passive Transport….. • 2. Osmosis—Movement of water from a higher

water concentration to a lower water concentration across a membrane; One molecule or ion displaces one water molecule. – A. tonicity—ability of a solution to change the shape

of a cell by altering volume of water. – B. hypotonic—solution with lower concentration of

solutes than the cell. – C. hypertonic—solution with higher concentration of

solutes than the cell. – D. isotonic—solution with same concentration of

solutes as the cell. – Video clip:

https://www.youtube.com/watch?v=w3_8FSrqc-I

Osmosis

Diffusion vs. Osmosis

Passive Transport

• 3. Facilitated Diffusion—carrier proteins change shape to carry large substances across the membrane; selective (glucose).

• Video: https://www.youtube.com/watch?v=vKGN_Zhz8AY

• 4. Filtration—Hydrostatic pressure forces water and solutes through a membrane (capillaries, urine).

2. Active Transport—requires energy (ATP) to move substances across the membrane.

• Criteria: too large, lipid insoluble, move against a concentration gradient.

• B. Vesicular (bulk) Transport—

• 1. Exocytosis (out of the cell)—Ex: hormone secretion, neurotransmitter release, mucus secretion, excrete wastes

• 2. Endocytosis (into the cell)

– A. Phagocytosis (cell eating)--macrophages

– B. Pinocytosis (cell drinking)—intestinal walls

• 3. Receptor Mediated Endocytosis– specific molecules are ingested into the cell. The specificity results from a receptor-ligand interaction. Receptors on the plasma membrane of the target tissue will specifically bind to ligands on the outside of the cell. An endocytotic process occurs and the ligand is ingested.

• Ex. Metabolism of cholesterol

Membrane proteins

Membrane Transport

Cell Division

• New cells can be formed only by the division of existing cells. A plant or animal starts as a single cell and grows by increasing the number of cells. The human body contains approx. 100 trillion cells, most of which are less than 1/10 mm across.

Cellular Metabolism

• An organism acquires energy by breaking down food within its cells. It then uses this energy to maintain each cell’s internal chemical environment, to build organic molecules, to grow, and to reproduce by cell division.

Cell Diversity • There are around 200 different cell types that

vary greatly in size, shape, and function.

• Life begins with one cell able to divide.

• Different chemical signals in the embryo direct cells into specific pathways of development.

• Cell DNA determines which proteins are made; cell specialization.

• New cells are formed throughout childhood and adolescence, although most organs are functional before birth.

1. Cells that connect body parts • A. Fibroblast—elongated shape that lies along cable-

like fibers that it secretes. It has a lot of ribosomes and a large golgi apparatus (to make and secrete the protein building blocks of these fibers.

• B. Erythrocyte (red blood cell)—carries oxygen in the bloodstream. Concave disc shape, so it has extra surface area to take up oxygen and is streamlined to move easily through the blood.

2. Cell that covers and lines body organs.

• Epithelial cells—hexagonal “honeycomb” shape so they can pack together in sheets. Has lots of intermediate filaments that resist tearing.

3. Cells that move organs and body parts.

• Skeletal Muscle Cells

• Smooth Muscle Cells

• Elongated shape; filled with abundant contractile filaments, so they can shorten forcefully and move bones or change the size of internal organs.

4. Cells that store nutrients

• Fat Cells—Huge spherical shape is produced by a large lipid droplet.

5. Cells that fight disease

• Macrophage (a phagocytic cell)—Extends long pseudopods (false feet) to crawl through tissue to reach infection sites. There are many lysosomes in the cell that digest microorganisms.

6. Cell that gathers information and controls body functions

• Nerve Cell (neuron)—long processes for receiving messages and transmitting them to other structures in the body. The processes are covered with an extensive plasma membrane, and a plentiful rough ER to synthesize membrane components.

7. Cells of reproduction

• Oocyte (female)-largest cell in the body…contains several copies of all organelles, for distribution to daughter cells that arise when fertilized egg divides to become embryo.

• Sperm (male)—long and streamlined, built for swimming, propelled by flagellum .

What are tissues? • Groups of similar cells that work together to perform a

common function. • There are 4 categories:

– Epithelial- linings and coverings of organs and body cavities, secretory part of organs and glands, transport membranes of capillaries and alveolar sacs, and membranes which lubricate organs.--covering

– Connective—supports as bone, cartilage, tendons, and ligaments, protects as the bony cavities and as protective immune cells in the blood, and stores nutrients.--support

– Nervous—carries information in the form of impulses throughout the body.--control

– Muscle—contracts to perform movements such as skeletal muscle movements, propulsion in the GI tract, and pumping blood in the heart.--movement

Video Clip: https://www.youtube.com/watch?v=tKWTJ3_-1E8

4 Types of Tissue

Epithelial • Epithelial tissue protects your body from moisture loss,

bacteria, and internal injury; form covering layers. • There are 2 types of epithelial cells: • A. Covering and lining epithelium covers or lines almost

all of your internal and external body surfaces; ex. Outer layer of skin and organs, internal surface lining of your lymph vessels and digestive tract.

• B. Glandular epithelium secretes hormones or other products such as stomach acid, sweat, saliva, and milk.

• Functions: Protection, Absorption, Filtration, Secretion • Epithelial Song

6 Characteristics of Epithelial Cells • 1. Tightly Packed; Specialized contacts—

desmosomes and tight junctions hold cells together.

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• 2. Cells have one free surface.

• Apical surface faces body’s exterior or a cavity.

• 3. Exposed surface may be slick—others have cilia or microvilli.

• 4. Lower surface rests on basement membrane. (Supported by connective tissue)

Epithelial

Connective

• 5. Cells have no blood supply of their own and depend on underlying connective tissue for food and oxygen.

6. Reproduce readily.

--cells are highly mitotic.

Video Clip: Epithelia

https://www.youtube.com/watch?v=Ucgm0qX4T0k

Epithelial Cells

• There are many types of epithelial cells. They are found on all body surfaces inside and out. Each epithelial cell is given two names. The first name indicates the number of cell layers and the second describes the shape of the cell.

• Number of Layers: Simple, Stratified

• Simple—only one cell layer thick

• Stratified—more than one cell layer thick

• Cell Shape: Squamous, Cuboidal, Columnar

• Squamous—flat and tile-like; like a fried egg

• Cuboidal—Spherical nuclei

• Columnar—rectangular with elongated nuclei

Epithelial Cell Shapes

Squamous- flat and tile-like Cuboidal—spherical nucleus

Columnar—elongated nuclei

Classified as simple or stratified by number of layers

Epithelial—Number of Layers

Simple Stratified

Epithelial Tissue

Epithelial Tissue

Simple Epithelia: absorption, secretion, and

filtration. Too thin for protection.

Simple Squamous:

• Single layer of flattened cells resting on basement membrane, disc shaped central nuclei.

• Fit closely together like floor tiles.

• Allows passage of materials (diffusion/filtration).

• Found in air sacs of the lungs (alveoli), walls of capillaries (nutrients and gases pass between tissues and blood), lining of heart

• Also form serous membranes, the slick membranes that line interior body cavities.

Simple Squamous

Simple Epithelial Tissues

Simple Cuboidal:

• One layer of cuboidal cells resting on a basement membrane.

• Common in glands and their ducts (ex. salivary gland and pancreas).

• Forms the walls of the kidney tubules and covers the surface of ovaries; parts of the eye and thyroid.

• Secretion and absorption.

Simple cuboidal

Simple Epithelial Tissues Simple Columner:

• Single layer of tall cells that fit close together; oval nuclei.

• Contain goblet cells, mucus secreting cells.

• Absorption, secretion, propel secretion (mucus, enzymes)

• Lines the entire length of digestive tract, from stomach to anus, gallbladder, uterus

• Epithelial membranes that line body cavities and open to the body exterior are called mucous membranes.

Simple Epithelial Tissues

Pseudostratified Columnar Epithlium:

• All of the cells rest on the basement membrane, but some of its cells are shorter than others, and their nuclei appear at different heights above the basement membrane. This gives the false impression that it is stratified.

• Function: Absorption and secretion.

• A ciliated variety lines most of the respiratory tract.

• The mucus produced by the goblet cells in this epithelium traps dust and other debris, and the cilia propel the mucus upward and away from the lungs.

Stratified Epithelial Tissues—2 or more

layers; more durable. Primary function is to protect.

Stratified Squamous:

• Most common stratified epithelium.

• Several layers of cells; surface cells full of keratin (dead).

• The cells at the free edge are squamous, but those close to basement membrane are cuboidal or columnar.

• Esophagus, mouth, and outer portion of the skin.

Stratified Epithelial Tissues

Stratified Cuboidal:

• Usually 2 layers with (at least) the surface being cuboidal.

• They protect areas such as the ducts of sweat glands, mammary glands, and salivary glands.

Stratified Columnar:

• Surface cells are columnar, but basal cells vary in size and shape.

• Also found in the ocular conjunctiva of the eye, in parts of the pharynx and anus, the female’s uterus, the male uretha and vas deferens, and intralobular ducts in salivary glands.

• Transitional Epithelium • A highly modified, stratified squamous epithelium that

forms the lining of only a few organs: the urinary bladder, the ureters, and part of the urethra. All of these are part of the urinary system and subject to stretching.

• Basal layer are cuboidal or columnar; those of free surface vary in appearance.

• Unstretched: membrane is many-layered, superficial cells are rounded and dome-like.

• Stretched and full: epithelium thins, surface flatten and become squamous-like.

• The ability of transitional cells to slide past one another and change their shape (transitions) allows the ureter wall to stretch as greater volume of urine flows through the tube-like organ. Thus, more urine can be stored.

Transitional Epithelium

• 10 or more layers of cuboidal cells

• Able to withstand tension changes/stretching

• Cells flatten when organ stretched

• Bladder

Glandular Epithelium

• A gland consists of one or more cells that make and secrete a particular product.

• The product is called a secretion, and typically contains protein molecules in an aqueous solution.

Glandular Epithelium • A. Endocrine glands-

• Lose their connection to the surface (duct); often called duct-less glands. Their secretions (all hormones) diffuse directly into the blood vessels that weave through the glands.

• Ex: thyroid, adrenals, and pituitary.

Glandular Epithelium • B. Exocrine glands-

• Retain their ducts, and their secretions empty through the ducts to the epithelial surface.

• Can be internal or external.

• Sweat and oil glands, liver, and pancreas.

Connective Tissue

Connects body parts. Found everywhere in the human body; most abundant

and widely distributed type of tissue. Functions: protecting, supporting, and binding together. Characteristics: 1. Variation in blood supply. (Most vascular, except

tendons and ligaments, making them slow to heal; cartilage are avascular.)

2. Cells have extracellular matrix—nonliving substance found outside the cells.

Vascularized: have good blood supply

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Connective Tissue

• Binds, supports, protects,

insulates, and transports

Extracellular Matrix • The extracellular matrix is produced by the

connective tissue cells then secreted to their exterior. It is made of a structure-less ground substance and fibers.

– Ground Substance

– Unstructured

– Serves as glue (allows

connective tissue cells to attach themselves to a matrix)

– Holds a lot of fluids • Nutrients can diffuse between blood and cells

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Structural Elements

• Ground substance – fluid, proteins

• Fibers

– Collagen – tough and strong (stronger than steel)

– Elastic – stretchy (rubber band)

– Reticular – network of thin fibers (support tissues of organs, allow more “give” than collagen)

• Connective tissue generally provides structure and support to the body.

• A. Bone • B. Cartilage--(Hyaline, elastic, fibrocartilage) • C. Dense or Fibrous connective tissue—also

holds body parts together, buts its structure is more rigid. Found in ligaments, tendons, cartilage, and bone.

• D. Loose connective tissue—holds structures together. Ex. Holds the outer layer of skin to underlying muscle tissue. Found in fat layers, lymph nodes, and red bone marrow.

• E. Blood

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Bone Tissue:Osseous Tissue • Supports, protects, stores, produces

– Hard, calcified, a lot of collagen, vascular

– Support, protect, lever for muscles to act on, stores calcium/minerals, marrow produces blood

• Two types: compact bone and spongy bone.

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Cartilage • Cartilage consists of a dense

matrix of collagen fibers and elastic fibers embedded in a rubbery ground substance. The matrix is produced by cells called chondroblasts, which become embedded in the matrix as chondrocytes. The surface of most of the cartilage in the body is surrounded by a membrane of dense irregular connective tissue called perichondrium. Cartilage contains no blood vessels or nerves (except in the perichondrium).

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1. Hyaline (“glassy”) Cartilage • Supports, cushions, and provides

flexibility.

• Most abundant

• Abundant collagen fibers hidden by a rubbery matrix with glassy (shiny), blue-white appearance.

• Provides smooth surfaces, enabling tissues to move/slide easily over each other, facilitating smooth movement at joints;

• Supporting structures of larynx (voice box), attaches to ribs of the breastbone, covers the ends of many bones forming joints, bronchi, bronchial tubes, nose, trachea.

• The skeleton of a fetus is largely hyaline cartilage, but it is bone by birth.

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2. Elastic Cartilage • More elastic fibers.

• Provides support to surrounding structures and helps to define and maintain shape. Flexibility/structure

• External ear, auditory tubes, epiglottis (lid on top of larynx)

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3. Fibrocartilage

• Similar to hyaline but more fibrous

• Absorbs shock, compressible

• Strongest and most durable

• Between vertebrae, meniscus of knee

Dense Connective (or dense fibrous) • Has collagen fibers as main matrix element

• Crowded between the collagen fibers are rows of fibroblasts that manufacture the building blocks of fibers.

• Lots of fibers, few cells.

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Dense Regular

• Dense connective tissue: dense regular

– Parallel collagen fibers

– Attaches muscle to bone

– Attaches bone to bone

– Withstands stress

– Tendons, ligament

Dense Irregular

– Irregularly arranged collagen fibers

– Withstands great tension, strong, can move in many directions

– Skin, digestive tract, joints

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1. Loose Connective Areolar • Most abundant CT

– Most widely distributed CT.

– Soft, pliable,gel-like “cobwebby”

tissue that cushions and protects the

organs it wraps. Lots of empty space.

– Binds skin to muscles, around organs,

surrounds capillaries and nerves.

– Lots of fibroblasts, macrophages • Several Functions

– Protection/cushion/support/binding/elasticity

– Functions as a universal packing tissue and connective tissue glue because it helps to hold the internal organs together and in their proper positions.

– It provides water and salt for surrounding tissue.

– Fights infection—swelling, puffiness of skin is due to macrophages.

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2. Loose Connective Adipose

Tissue/ FAT

• Each adipocyte cell is filled with a single, large droplet of fat. Its cytoplasm, nucleus, and other components are pushed toward the edges of the cell.

• Storage for excess food

• Insulates body and protects it

from bumps, heat, and cold.

• Protects some organs:

kidneys and eyeballs and

found in thick layer under skin.

3. Loose Connective Reticular Tissue

– Network of reticular fibers in a loose ground substance

– Form a soft skeleton that supports other cells (white blood cells, macrophages)

– Lymphoid organs lymph nodes, bone marrow, spleen

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Blood

• No ground substance or fibers

• Blood cells surrounded by nonliving, fluid matrix called blood plasma. – Erythrocytes

– Leukocytes

– Thrombocytes

• Transportation for cardio-

vascular system, carrying

nutrients, waste, gases, etc.

Recap of Connective Tissue

Muscle • It contracts and expands, moves bones and organs. • Made of muscle fibers. • A. Skeletal (striated) muscles—

– 1. Attached to skeleton. – 2. Controlled voluntarily. – 3. Causes gross body movement.

B. Cardiac Muscle— 1. Found in the heart. 2. Involuntary.

• C. Smooth (involuntary) muscle— – 1. lines the walls of blood vessels and certain organs such as the

digestive and urogenital tracts. – 2. Contracts much more slowly than other muscle types. – 3. Involuntary.

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3 Types of Muscle Tissue

–Skeletal – attached to bones

–Smooth – walls of organs, blood

vessels, etc.

–Cardiac - heart

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Skeletal Muscle

• Control voluntary motion.

• Attached to the skeleton. When they contract, they pull on bones or skin, resulting in gross body movements or changes in facial expression.

• The cells are long and narrow, multinucleate, and have obvious striations (stripes).

• Because they are elongated to provide a long axis for contraction, they are often called muscle fibers.

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Smooth Muscle

• Function – propulsion

• No striations (aka visceral)

• 1 nuclei and are spindle

shaped (pointed at each end)

• Tightly packed into a sheet

• Involuntary

• Found in walls of hollow

organs, such as stomach,

uterus, and blood vessels.

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Cardiac Muscle • Only in the heart; propels

blood through blood vessels. • Involuntary • Striated, one nucleus • Relatively short, branching

cells that fit tightly together (like clasped fingers) at junctions called intercalated disks. They contain gap junctions that allow ions to pass freely from cell to cell, resulting in rapid conduction of electrical impulses across the heart.

Nervous • Forms the nervous system, which is responsible for

coordinating the activities and movements of your body through its network of nerves. Includes the brain, spinal cord, and nerves that branch off of those two key parts.

• A. Neurons—basic structural unit of CNS. Each cell consists of the cell body, dendrites, and axon.

• B. Neuroglia (glial cells)—insulate and protect the delicate neurons or anchoring neurons to blood vessels.

• Functions: irritability and conductivity • Neurons receive and conduct electrochemical

messages from one part of the body to another.

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What is Nervous Tissue? • Their cytoplasm is drawn out into long

processes (extensions), as much as 3

feet in the leg, which allows a single

neuron to conduct an impulse over

long distances in the body.

Tissue Repair

• 1. Inflammation

– Tissue DRAMA! Injured cell releases chemicals

– Chemicals cause tissue to dilate more permeable

– White blood cells/plasma/antibodies seep into area

– Construct a clot

Tissue Repair

• 2. Organization restores blood supply

– Clot is replaced by granulation tissue (delicate pink tissue that contains capillaries)

– Granulation tissue bleeds easily (pick at a scab)

– Produce growth factors

– Becomes scar tissue (highly resistant to infection bacteria inhibiting substances)

Tissue Repair

• Regeneration/fibrosis

– Epithelium regenerates

– Scar may be visible or invisible