Pathophysiology

Dr. Yahya Ibn Ilias

Pathophysiology ?

= Abnormal physiology + Abnormal biochemistry

Pathophysiology =

Explore the rule of origin and evolution of disease processes and the underlying mechanisms.

(Basing on physiology and biochemistry)

?Basic medicine

Clinical medicine

2. Why to study Pathophysiology ？

Explain “Why and How” of diseases

Why Is Pathophysiology Important?

An essential introduction to clinical medicine.

A bridge: basic medicine and diseases.

Enables us to understand why and how diseases develop and various clinical manifestations appear.

What are the underlying mechanisms, and in so doing devise rational therapeutics.

Disease

1. Concept of Disease

Aberrant manifestation of deregulated homeostasis caused by harmful agents.

The development of a disease is a pathologic process with a characteristic set of signs and symptoms involved in the whole body or any of its parts.

Concept of Health

Without any evidence of disease, and a state of complete well-being Physically, Socially and Psychologically. ----- WHO

2. Etiology of Disease

Etiology is to study the causative agents, Answer the question why disease happens.

Complete well-beingComplete well-beingPhysically Physically Socially Socially PsychologicallyPsychologically

Extrinsic FactorsExtrinsic Factors

Intrinsic FactorsIntrinsic Factors

Predisposing factorsPredisposing factors

Precipitating factorsPrecipitating factors

Extrinsic FactorsExtrinsic Factors

The extrinsic causes include : 1. Biological agents

2. Chemical agents

3. Physical agents

4. Nutritional imbalance

Intrinsic FactorsIntrinsic Factors

Intrinsic causes consists of

1. Genetic factors

2. Congenital factors

3. Immunological factors

4. Psychological factors

3. Pathogenesis of diseases

General rules for pathogenesis of diseases

1. Disruption of homeostasis.

2. Process of damage and anti-damage.

3. Reversal role of cause and result.

4. Correlation between systemic and local regulations.

Neural regulationsNeural regulations

Humoral regulationsHumoral regulations

Cellular regulationsCellular regulations

Molecular regulationsMolecular regulations

Basic Mechanisms for Disease

4. Phases of Diseases

LatencyProdrome

RecoveryDiseaseDisease

Clinical symptoms

Outcome of Disease

Outcome of a disease

Recovery

Death

Complete recovery

Incomplete recovery

Death

The body as a whole stops working forever.

Brain death is the marker for the diagnosis.

Brain Death (WHO criteria)

Cessation of spontaneous respiration.

Irreversible coma.

Absence of cephalic reflexes.

Dilated or fixed pupils.

Absence of any electrical activity of the brain.

Absence of brain blood flow

Body fluid, Electrolytes balance and imbalance

Fluids and Electrolytes are present in body cells, in the tissue spaces between the cells, and in the blood that fills the vascular compartment.

Body fluids serve to transport gases, nutrients, and wastes; help to generate the electrical activity needed to power body functions; take part in the transforming of food into energy.

COMPOSITION AND COMPARTMENTALDISTRIBUTION OF BODY FLUIDS

Body fluids are distributed between the Intracellular fluid (ICF) and Extracellular fluid (ECF) compartments.

The ICF compartment is the larger of the two

compartments, containing approximately two thirds of the body fluid in healthy adults.

The remaining one third of body water is in the ECF

compartment, including that in the interstitial or tissue spaces and blood vessels.

The ECF, including the plasma and interstitial fluids,contain large amounts of sodium and chloride, moderate amounts of bicarbonate, but only small quantities of potassium.

In contrast to the ECF fluid, the ICF contains sm

all amounts of sodium, chloride, and bicarbonate and large amounts of potassium.

Osmolality of body fluids

The cell membrane is highly permeable to water but relatively impermeable to most solutes.

Osmosis : The tendency of a fluid, usually water, to pass through a semipermeable membran

e into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane.

Osmotic pressure :

The amount of pressure required to oppose the osmosis is termed as Osmotic pressure.

Osmole : the total number of particles in a solution is measured in terms of “Osmoles”.

Osmolality : the concentration of an osmotic solution especially when measured in osmols or milliosmols per KG of water.

Osmolarity : the concentration of an osmotic solution especially when measured in osmols or milliosmols per Litre of water.

Tonicity. A change in water content causes cells to swell or shrink.

Water balance

Regardless of age, all healthy persons require approximately 100 mL of water per 100 calories metabolized for dissolving and eliminating metabolic wastes.

This means that a person who expends 1800 calories for energy requires approximately 1800 mL of water for metabolic purposes.

(The metabolic rate increases with fever; it rises approximately 12% for every 1°C (7% for every 1°F) increase in body temperature.)

Mechanisms of Regulation of Water Balance

Disturbance

Volume

Osmotic pressure

ADHRAASThirst

Thirst ADHRAAS

Regulation pathway

Thirst

Thirst is controlled by the thirst center in the hypothalamus.

There are two stimuli for true thirst based on w

ater need:

(1) cellular dehydration caused by an increase in extracellular osmolality and

(2) a decrease in blood volume,

Sensory neurons, called osmoreceptors, which are located in or near the thirst center in the hypothalamus, respond to changes in extracellular osmolality by stimulating the sensation of thirst.

The regulation of ADH

ADH released

BP/Blood volume

+Stretch receptor

+

Plasma osmotic pressure

+Osmoreceptor

reabsorption↑ of free water in renal tubules

RAAS

To be continued……..