Every living organism is made up of units called cells.

These are tiny structures seen only through the microscope.

Cells are held together by special, intercellular material.

In the human body there are approximately 100 trillion cells.

The cells differ according to the function, which they do.

For example, the blood, muscle, and all cells have certain features in common.

All cells use oxygen from the air we breathe and substances from the food we eat to produce energy.

Production of waste material is common to all cells.

Also most cells can produce new cells, an whenever a cell dies (for whatever reason) new cells are formed.

In order to be able to produce energy, give rise to waste substances, and form new cells when needed, cells have tiny, specialized structures inside them, which can be observed with a very powerful microscope.

SIMPLEST FUNCTIONAL UNIT

CELL

A collection of cells all of which perform the same function is called tissue.

For example muscle (tissue) is made up of muscle cells, all of which can contract.

SEVERAL CELLS

TISSUE

A tissue is an organized group of cells of different types as well as their extracellular material (matrix)

There are only 4 classes of tissue :

epithelial tissue covers surfaces (e.g., skin, lining of body cavities, lining of hollow organs like bladder, stomach)

muscle tissue performs work or alters the shape of an organ

nervous tissue includes neurons and their support cells (called neuroglia)

connective tissue is all the rest (e.g., blood cells, bone & cartilage cells) cells & matrix that fill body spaces and bind tissues together

A collection of tissues forming a structure which has a particular function, is called an organ.

For example, the stomach has muscular, glandular, and other tissues, and is concerned with the churning (mixing) of food and digestion (breaking

down of food into

simple substances

which the body can use).

SEVERAL TISSUES

TOGETHER

ORGAN

Several organs, each performing a specific function, together make a system.

Each system has a particular part to play, in the overall functioning of an individual.

SEVERAL ORGANS

TOGETHER

SYSTEM

For example the digestive system has many organs.

Among them are – the mouth (chew and moisten food), esophagus (deliver food to stomach), stomach (grind

and dissolve food), small

intestine (finishes digesting

food and absorbs

nutrients), large intestine

(reabsorbs water to prevent

loss), and rectum

(stores feces).

THE DIFFERENT SYSTEMS – AN OVERVIEW

Before discussing the different systems we should know that about 56% of our body is made up of fluid.

Most (66%) of the fluid is inside the cells.However, 33% is outside the cells and called

extracellular.

THE CIRCULATORY SYSTEM= heart + blood vessels such as the arteries & veins

Is a transport system for the blood.The blood carries essential substances to all the

cells so that they can perform their functions.Two essential substances are oxygen and

glucose.The circulatory system also transports waste

substances from the cells to other organs, where they are excreted (removed from the body).

HEARTBlood vessels

conduct O2, Co2, & sugar (in blood)

Pumps blood

Body cells

Use O2 and sugar

THE RESPIRATORY SYSTEM= nose, larynx, pharynx, trachea, bronchi, & lungs

This system is concerned with making the necessary gas (oxygen) available from the air around us, and removing the unnecessary gas (carbon dioxide), as we breathe out.

Respiratory system

Atmosphere

O2

Rest of the body

CO2

Respiratory system (Exchange of Gases)

THE DIGESTIVE SYSTEM= mouth-teeth, tongue, pharynx, esophagus,

stomach duodenum, small intestine, large intestine, colon, rectum, liver, gallbladder, & pancreas

This system is concerned with breaking up the food which we eat into smaller parts which can enter the blood, and be used to build up the body and provide energy.

THE EXCRETORY SYSTEM= kidneys, ureters, urinary bladder

Is concerned with removal of the unnecessary and toxic substances.

The skin also helps, by secretion of sweat.Wastes are also removed through digestive and

respiratory systems.

THE NERVOUS SYSTEM= brain, spinal cord, nerves

Controls all the other systems. It is concerned with control of the most basic

activities such as the beating of the heart and the formation of urine, to the most complex – such as writing a novel.

As a control system the nervous system has to get information both from outside as well as from within the body.

This is possible because of the special senses (vision – eyes, hearing – ears, touch – skin, taste – tongue, smell – nose) which give the brain detailed information about the outside world.

Similarly, there are sensors which give the brain detailed information about the ‘inner world’ – where our body is positioned in space, how tightly our fingers are clenched, and so on.

THE WORLD OUTSIDE

Nervous System (overall control)

NOSE SKIN

EYES

EARS

TONGUEmuscles

BRAINReceives informationSends messages

THE ENDOCRINE SYSTEM= glands – pituitary, thyroid, ovaries, testes

Is essential for the normal functioning of other systems.

For example if the thyroid gland functions less efficiently than it should, the person may be mentally slowed down, feel lazy and sluggish, gain weight, and be altogether unwell.

The endocrine system is also under the control of the brain.

Endocrine Glands

THE REPRODUCTIVE SYSTEM= reproductive glands + reproductive organs

Is closely regulated by the endocrine system, i.e. the ovaries secrete hormones (chemical substances) which cause changes in the uterus during menstruation.

In Man reproductive activates are controlled by the brain to a large extent.

THE MUSCULOSKELETAL SYSTEM= skeletal + muscles

Gives protection to soft and important organs.For example, the skull protects the brain, the rib

cage protects the heart and lungs.Muscles are of course necessary for movement.

Heart & Lungs

Ribcage surrounds & protects

Muscle bone

THE IMMUNE SYSTEMConsists of cells which move around in the

body, and collections of cells which have fixed positions.

This system is mainly a defense system.The cells of the immune system are the soldiers

who fight against germs.

TERMS USED IN ANATOMY

Superior - toward the head Inferior - away from the headAnterior - the front of the

body or body partPosterior - the back of the

body or body partMedial - toward the midline

that divides left and rightLateral - to the side away

from the midline

Proximal - closer to the torsoDistal - farther away from the

torso

Anatomical position - standing erect, facing the observer, arms are at the sides with palms facing forward.

Many parts of the body are symmetrically arranged.

For eg., the right and left limbs are similar, there are right and left eyes and ears, right and left lungs, and right and left kidneys.

But there is also a good deal of asymmetry in the arrangement of the body.

The spleen lies entirely on the left side; the largest part of the liver lies on the right side, the pancreas lies partly on each side.

The human body is studied from the erect position with the arms by the sides and the palms of the hands facing forwards, the head erect and eyes looking straight in front.

This is described as the anatomical position.The various parts of the body are described in

relation to certain imaginary lines or planes.The median plane runs through the centre of

the body.The terms internal and external are used to

describe the relative distance of an organ or structure from the centre of the cavity.

Anatomical Position

Eg., the internal carotid artery is within the cranial cavity and the external is outside the cavity.

The terms superficial and deep are used to denote relative distance from the surface of the body, and the terms superior and inferior denote positions relatively high or low, particularly in relation to the trunk, such as the superior and inferior surfaces of the clavicle.

The terms anterior and posterior are synonymous with ventral and dorsal.

The terms proximal or distal are employed to describe nearness to or distance from a given point.

When three structures are in a line running from the medial plane of the body outwards, they are described as being placed in medial, intermediate, and lateral positions.

Similarly three structures run from front to back – anterior to posterior or from downwards – superior to inferior.

SYSTEMS IN THE BODY

According to the functions they perform andUnder the heading of the different terms

employed to indicate the knowledge of certain parts.

Systematic anatomy or the division of the body into systems is arranged:

ExampleOsteology – is a knowledge of – bones.Myology – is a knowledge of – muscles.Neurology – is a knowledge of – nerves and

nerve structure.

INTRODUCTION TO THE CHEMISTRY OF LIFE

Living systems obey chemical and physical laws.

For example, energy transformations in the cell occur by the formation and breaking of chemical bonds.

These chemical reactions result in the reorganization of subatomic particles.

The element carbon forms a vast number of compounds.

Over 16 million carbon-containing compounds are known, and about 90% of the new compounds synthesized each year contain carbon.

The study of carbon compounds constitutes a separate branch of chemistry known as organic chemistry.

This term arose from the 18th century belief that organic compounds could be formed only by living systems.

This idea was disproved in 1828 by the German chemist Friedrich Wohler when he synthesized urea (H2NCONH2), an organic substance found in the urine of mammals, by heating ammonium cyanate (NH4OCN), an inorganic substance.

The notion that organic chemicals and living organisms are connected is certainly true in one sense: Life as we know it could not exist without a vast array of complex, biologically important organic molecules. The study of the chemistry of living species is called biological chemistry, or biochemistry.

Life is recognized by certain characteristics:Metabolism:

The sum of chemical processes in an organismAnabolism = chemical reactions that build-up

or synthesizeCatabolism = chemical reactions that break-

down or fragment

Equilibrium exists when the organism is in "steady state",

i.e., amount of anabolism equals amount of catabolism. eg: healthy adult is in steady state; eg: growing healthy child is in anabolic state

Responsiveness: Ability to detect and respond to external stimuli eg: afferent nervous system monitors external

environment, and then the efferent nervous system alters the body to accommodate the environment.

Movement: Displacement of the whole organism as well as

rearrangement of the relative positions of the organism's parts

eg: skeletal muscle impels legs to run; eg: smooth muscle causes intestine to move food along.

Growth: Increase in organism size (may be cyclical as in

bacteria) caused when anabolism exceeds catabolism.

Differentiation Is mostly present in multicellular organisms.

Different cells or tissues or organs specialize to perform one function and lose the ability to perform any other function.

eg: lymphocytes in the blood detect and respond to foreign materials in the body (e.g., bacteria); they are not able to carry oxygen or phagocytose debris or cause the blood to clot.

Reproduction: Forming new cells to replace damaged or

senescent cells or even to "replace" the whole organism.

eg: sperm and ova can result in a baby; eg: "stem cells" in your epidermis can reproduce to replace the damaged epithelium when you injure your skin

Homeostasis in the normal, healthy, adult state = equilibrium

A major mechanism for homeostasis is communication and exchange of materials between intracellular fluid (ICF), interstitial fluid (between cells) and plasma (the liquid portion of blood).

(Extracellular fluid (ECF) = plasma plus interstitial fluid.)

A major mechanism for homeostasis is "negative feedback“

Negative Feedback: a specific stimulus causes a specific response, and the response "fixes" (i.e., reverses) the stimulus.

Stimulus and response mechanisms are

commonly hormones and nerves

eg: stimulus is scary situation, response is secretion of hormone adrenalin which sends blood and oxygen to heart, lungs, and muscles so you can escape, result is decrease in adrenalin due to escape from the original stimulus; blood and O2 transport return to resting state

eg: sensors in the tendons of your legs detect stretching when you are about to lose your balance, reflex neuron causes contraction of the muscle attached to the tendon, muscle pulls you upright & releases the stretch stimulus, result is restoration of balance

Positive feedback: specific stimulus causes a specific response that makes the stimulus even stronger even stronger response….

note: this can be a vicious circle unless something else ("termination mechanism") intervenes.

eg: stretching of cervix during childbirth stimulates secretion of hormone (oxytocin) which causes uterus to contract and stretch the cervix even more, etc.

Here the "termination mechanism" is baby's birth which interrupts the feedback by eliminating the source of cervical stretching.

Feedback systems always involve 3 components:

receptor - senses the stimulus

control center - interprets the stimulus & determines response

effector - produces the response If any of the 3 components is missing or

malfunctions, then the feedback system won't work.

eg: Site in the hypothalamus of the brain is responsible for keeping the body at 37oC (98.6oF) by regulating heat loss through the skin, breath, etc.

When bacterial toxins are released into the body, chemicals called prostaglandins are produced which cause the hypothalamus to set the equilibrium temp at a higher value.

Bacterial infections cause fever (“failure” of temperature equilibrium).