POST LABORATORY DISCUSSION

Exercise 1. The Scientific MethodExercise 2. The Compound Microscope

Exercise 3. The Typical Animal CellEx 4. Physico-chemical Properties of the Protoplasm

Exercise 5. Cell Division: MitosisExercise 6. TissuesExercise 7. Organs

Exercise 1The Scientific Method

The Scientific MethodObserve

Define the problem

Formulate hypothesis

Experiment Gather data

Analyze data

Draw conclusion

The Scientific Method

• A problem is considered scientific – if it can be resolved by gathering

observable and measurable evidence – if the method of resolving it is

repeatable

Limitations of Science

• Science can't answer questions about: • VALUE

– eg. Science cannot evaluate aesthetic value: Which is prettier? A rose or a tulip?

• MORALITY

– eg. Science cannot decide whether abortion is good or bad.

• THE SUPERNATURAL or THE PARANORMAL– eg. Science cannot explain the existence of God, elves or

ghosts.

fancher2@cdnet.cod.edu

Theories, Hypotheses and Principles

• Theories versus hypotheses

– Theories summarize repeatedly-tested hypotheses into a coherent, supportive structure.

– Theories are more certain and more accepted than hypotheses.

• Principles

– Principles are laws or facts of nature based on evidence.

– eg. The general principle of causality: effects are analyzed to establish and describe the cause.

Exercise 2The Compound Microscope

Compound MicroscopeSimple Microscope

• Has only one magnifying lens• No objectives

• Has two magnifying lenses – Oculars / eyepiece– Objectives

• The letter ‘e’ is inverted when viewed under the microscope because the optical magnification inverts the virtual image of the specimen.

The Compound Microscope

Lens

Specimen

The Compound Microscope

• Slide is moved to the left.

• Slide is moved to the right.

• Slide is moved up.

• Slide is moved down.

The Compound Microscope

• Low power objective (LPO) covers a wider field.

• High power objective (HPO) gives a larger image.

LPO HPO

LPO HPO

• Shifting from LPO to HPO narrows the microscope field a certain portion is further magnified.

• Microscopy enables us to view and magnify microscopic organisms and structures which cannot be seen by the naked eye.

The Compound Microscope

• Base• Pillar• Arm • Inclination joint• Stage• Body tube• Draw tube• Revolving

nosepiece• Course

adjustment knob• Fine adjustment

knob

• Eyepiece / ocular• Objectives

– Scanner– LPO– HPO– OIO

• Mirror• Substage

– Iris diaphragm– Condenser

MECHANICAL OPTICAL

ILLUMINATING

The Compound Microscope

Exercise 3The Typical Animal Cell

• The endoplasmic reticulum is the “circulatory system” of the cell because it initiates the transport of membranes and proteins in the cell.

• The ER manufactures the membranes which later transit from the ER to the Golgi apparatus via transport vesicles.

• The Golgi apparatus then refines the products and further ships them to the other parts of the cell through transport vesicles.

The Cytomembrane System

• Centrosome – a region near the nucleus where a pair of centrioles is confined.

• During cell division, centrosomes and centrioles form the microtubules (mitotic spindle fibers) which align the chromosomes and separate the sister chromatids.

Centrosomes and Centrioles

The Typical Animal Cell

Mammalian RBCs are enucleated.

Red Blood Cells (RBCs)

RBCs of other vertebrates are nucleated.

• Discoveries of Robert Hooke, Anton van Leeuwenhoek, Matthias Schleiden and Theodore Swann gave rise to the Cell Theory which states that:

1. All living things or organisms are made of cells.

2. New cells are created by old cells dividing into two.

3. All cells are similar to each other, but not identical.

4. Cells are the basic building unit of life.

The Cell Theory

Exercise 4The Physico-chemical Properties of the Protoplasm

Physical Properties of the Protoplasm

• Colloidal Theory – The protoplasm is a fluid-colloidal system with the gel and

sol phases.

• The protoplasm is jelly-like, translucent, colorless, slimy and viscous.

• The protoplasm exhibits the Brownian Movement: colloidal particles move in a zigzag fashion because of the solvent molecules bombarding them.

• The protoplasm exhibits the Tyndall Effect: colloidal particles scatter light.

Chemical Properties of the ProtoplasmInorganic components

• Water

• CO2

• Acids• Bases• Salts • Minerals

Organic components

• Carbohydrates

• Fats

• Proteins

Physiological Properties of the Protoplasm• The nature of the protoplasm may vary from one cell to another depending on the function and activities of the cell.

• Components remain suspended in the protoplasm.

• Colloidal components tend to absorb solutes diffusing into the protoplasm.

• The semi-permeable plasma membrane bounding the protoplasm governs the entry and exit of water molecules into and out of the cell during osmosis.

Osmosis and Diffusion

Osmosis

• the entry and exit of water molecules thru the plasma membrane from a region of higher concentration to a region of lower concentration

Diffusion

• the entry and exit of solute molecules thru the plasma membrane or their scattering in the cell from region of higher concentration to a region of lower concentration.

Osmosis

• Only certain solute particles can pass thru the semi-permeable plasma membrane giving the water molecules the opportunity to enter and exit the cell.

Phagocytosis and Pinocytosis

• Phagocytosis: the cell with its pseudopodia engulfs big solid particles such as bacteria, cellular components and macromolecules.

• Pinocytosis: the cell engulfs small fluid particles through invaginations in its plasma membrane.

• Both processes involve vesicles pinching off from the plasma membrane.

• Tests for the presence of carbohydrates

– Monosaccharides – Benedict’s solution

– Polysaccharides – Iodine

– Sugars – Anthone test Tests for the presence of fats

Grease Spot Test Dye Test

Chemical Properties of the Protoplasm

Tests for the presence of proteins Coagulation Biuret test

Karyokinesis and Cytokinesis• Karyokinesis

– division of the nucleus

– mitosis itself

• Cytokinesis

– division of the cytoplasm

– cytoplasm begins to pinch in the middle through cleavage furrow during telophase

– proceeds even after mitosis until the two daughter cells are apart

Significance of Mitosis

• Growth

• The number of cells within an organism increases by mitosis.

• Cell Replacement

• Cells that die and sloughed off either naturally or by injury are replaced with new ones through mitosis (eg. epidermal cells, hematopoiesis, spermatogenesis)

• Regeneration

• Some animals can regenerate parts of the body through mitosis.

Significance of Mitosis

• The role of mitosis in the repair of tissues

Mitosis for the replacement of damaged tissues.

Duration of Mitosis

• Interphase - 20 mins

• Mitosis – Prophase - 105 mins– Metaphase - 13 mins– Anaphase - 8 mins– Telophase - 54 mins

• Mitosis itself may take an average of 80 mins, in some species 1 – 2 hours, in others it may be shorter or longer.

• Longest stage: Prophase

• Shortest stage: Anaphase

Exercise 6Tissues

Cilia vs. Flagella

Cilia Flagella

Hair-like processes on the surface of certain cells.

eg. cilia of the epithelial cells lining the trachea

Usually a single thread-like process extending from the surface of certain cells.

eg. the flagella of sperm cells

Beating motion Propeller-like motion

Position of Nucleus

Squamous cells tend to have horizontally flattened, elliptical nuclei at the center because of the thin flattened form of the cells.

Cuboidal cells have spherical nucleus in the center.

Columnar cells have elongated nuclei which are usually located near the base of the cells.

Adipose Tissue• The nuclei of adipose cells are located at the edge of the cytoplasm, close to the plasma membrane.• Large fat droplets push the nuclei to the plasma membrane.

Muscular Tissue

Thrombocytes• Thrombocytes or platelets aggregate and release factors which promote blood

coagulation when there is a bleeding wound.

• When bleeding occurs, chemical reactions change the surface of the platelet to make it “sticky”. Sticky platelets adhere to the wall of the blood vessel at the site of bleeding forming a “white clot.”

• Blood proteins produce fibrin strands which stick to the vessel wall forming a web. RBCs are then caught up in this web, forming a “red clot.”

Phagocytosis and Pseudopodia

• Phagocytosis

– A cell engulfs big solid particles such as bacteria, cellular components and macromolecules.

• Pseudopodia

– Temporary cytoplasmic extensions of a cell doing phagocytosis.

Diapedesis

• The migration of white blood cells across the endothelium of blood vessels to fight infection in the tissues surrounding blood vessels during an injury or trauma.

Tissues• Epithelial tissue

– with basement membranes

• Connective tissue

– cells are scattered in the matrix

• Muscular tissue

– contraction

• Vascular tissue

– transport materials

• Nervous tissue

– Receive impulses

Exercise 7Organs

Artery vs. Vein

Artery is thick-walled.Vein is thin-walled.

Molting• Arthropods, crustaceans, reptiles and birds undergo

molting or ecdysis for them to grow out of their rigid exoskeleton or skin.

• Mammals do not molt but the dead keratinized cells on the surface of their skin may be removed by scrubbing or they can be left to be shed on their own.

Oxygenated vs. Deoxygenated Blood

• Oxgenated blood – travels away from the heart to the different

arteries of the body– appears bright red because oxygen causes

hemoglobin molecules to turn from blue to red

• Deoxgenated blood – travels back to the heart to be resupplied with

oxygen– appears very dark red because so many of the

hemoglobin molecules have turned blue again

Structure and Function of Organs

• Arteries – thick-walled; blood pressure and contraction of muscles and elastic fibers propel blood from the heart to the arteries of the body

• Veins – thin-walled; relaxed flow of unoxygenated blood back to the heart• Capillaries – small but numerous to increase surface area for exchange

of materials between blood and tissues

•Blood Vessels

Blood Vessels

Skin

• Epidermis – highly stratified and has many types of cells for various functions: prevent dehydration, infection and penetration of UV rays, for sensation, for division of epidermal cells

• Dermis – connective tissue with blood vessels, nerve endings, hair follicles and various glands also for various functions

• Hypodermis – with adipose tissues for insulation

• Microvilli within villi – absorption of nutrients from the digested food• Goblet cells – secretion of intestinal juice for final digestion• Smooth muscles in tunica muscularis – contractions for passage of bolus

Small Intestine

• Rugae with gastric glands and gastric pits – secretion of gastric juices for digestion

• Smooth muscles in tunica muscularis – for distention, churning of food

Stomach

Liver

• Hepatocytes – polygonal; absorb nutrients from the small intestine and release them to bloodstream; converts glucose to glycogen and vice-versa

• Blood vessels – for the transport and exchange of nutrients and materials in the liver

• Bile capillaries and bile ducts – for the transport of bile salts manufactured by the liver to the small intestine for the emulsification of fats

Kidney • Nephrons in the cortex and medulla – filtration of waste materials from blood; concentration of wastes in urine

• Uriniferous tubules – conveys urine to the renal pelvis where it is further drained to the ureter

• Renal artery – delivers blood to the kidney for filtration

• Renal vein – drain cleansed blood from the kidney

• Adrenal glands – secrete aldosterone for maintaining concentration of solutes entering the bloodstream, cortisol for regulating overall metabolism and adrenaline usually for an emergency response

Ovary

• Follicles in the cortex – in which oocytes develop through oogenesis until they are released from the ovary

Testes

• Seminiferous tubules – where sperm cells are produced through spermatogenesis and washed off

Spinal Cord

• Gray matter – having mostly nerve cells

• White matter – having the supportive cells (neuroglia) that nourish the nerve cells

• Connected with sensory and motor nerves