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ANATOMY & PHYSIOLOGY

BY MR. LANGAT

Course outline

• See Ross and Wilson Anatomy and Physiology

and Health and Illness, 11th^ Edition.

INTRODUCTION

• Anatomy : study of the structure of the body and the

physical relationships involved between body parts.

• Physiology: study of how the parts of the body work,

and the ways in which they cooperate together to

maintain life and health of the individual.

• Pathology : study of abnormalities and how they affect

body functions, often causing illness.

• Pathophysiology : is a convergence of pathology and

physiology. It’s a discipline which explains the

physiological processes or mechanisms whereby

disease(pathology) develops and progresses.

• NB: WE SHALL BE DISCUSSING ABOUT THE NORMAL

ANATOMY AND PHYSIOLOGY 5

ORGANISATION OF THE HUMAN BODY

• OBJECTIVES
• By the end of this section you will be able to:
  • Describe the cell and its functions
  • Describe cell multiplication
  • Describe the transfer of substances across cell membranes
  • Describe tissues and their functions
  • Describe body fluids and electrolytes

• Levels of structural complexity

Ct…..

10

• Absorption – passage of substances through membranes and into body fluids
• Circulation – movement of substances in body fluids
  • Assimilation – changing of absorbed substances into chemically different forms
• Excretion – removal of wastes produced by metabolic reactions
• Digestion – breakdown of food substances into simpler forms

Maintenance of Life

• Life depends on five (5) environmental

factors:

• Water
• Food
• Oxygen
• Heat
• Pressure

Requirements of Organisms

• Oxygen (gas)
  • one-fifth of air
  • used to release energy from nutrients
• Heat
  • form of energy
  • partly controls rate of metabolic reactions
• Pressure
• application of force on an object
• atmospheric pressure – important for breathing
• hydrostatic pressure – keeps blood flowing

Internal environment and homeostasis

• External environment;
  • surrounds the body
  • provides the oxygen and nutrients required by all the cells of the body.
  • Its where waste products of cellular activity are excreted into
• The skin provides a barrier between the dry external environment and the watery environment of most body cells.
• I nternal environment: water-based medium in which body cells exist.
• Cells are bathed in fluid called interstitial or tissue fluid. Oxygen and other substances they require must pass from the internal transport systems through the interstitial fluid to reach them.
• Similarly, cell waste products must move through the interstitial fluid to the transport systems to be excreted. (^14)

A cell with a semi-permeable membrane

HOMEOSTASIS

• Def: the maintenance of the internal environment in a fairly constant state within narrow limits.
• Maintained by control systems which detect and respond to changes in the internal environment.
• A control system has 3 basic components:
  • detector,
  • control centre
  • Effector(s)
• Control centre:
  • determines the limits within which the variable factor should be maintained.
  • receives an input from the detector or sensor,
  • integrates the incoming information_._
• When the incoming signal indicates that an adjustment is needed the control centre responds and its output to the effector is changed. This is a dynamic process that maintains homeostasis. 17

Negative feedback mechanisms

• In systems controlled by negative feedback the

effector response decreases or negates the effect of

the original stimulus, restoring homeostasis.

• E.g; When body temperature falls below the preset

level, this is detected by specialised temperature

sensitive nerve endings. They transmit this

information as an input to the hypothalamus of the

brain which form the control centre.

• The output from the control centre activates

mechanisms that raise body temperature

(effectors).

• These include:
  • stimulation of skeletal muscles causing shivering
  • narrowing of the blood vessels in the skin reducing the blood flow to, and heat loss from, the peripheries
  • behavioural changes, e.g. we put on more clothes or curl up.
• When body temperature rises to within the normal

range, the temperature sensitive nerve endings no

longer stimulate the cells of the control centre and

therefore the output of this centre to the effectors

ceases.

• Most systems are controlled by negative feedback