Essentials of Anatomy and Physiology (Unit 1)

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Essentials of Anatomy and

Physiology FOR GENERAL PRACTITIONERS AND HEALTH

CARE MEMBERS

UNIT 1

INTRODUCTION AND

ORGANIZATION OFHUMAN BODY

BY

DR. ABDEL-MONEM A. HEGAZY (M.B. 1983, Dipl."Gynaecology and Obstetrics "1989, Master "Anatomy

and Embryology "1994, M.D. "Anatomy and Embryology "1999)

Associate Professor of AnatomyFaculty of Medicine, Zagazig University (A.R.E.) &

Al-Majmaa, College of Health Sciences, King Saud University (K.S.A.)



INTRODUCTION

Anatomy is the study of the structure of the human body,

while, physiology is the study of the functions of its organs.

The two sciences are related together i.e. the structure of an

organ suggests its function; also the function suggests the

structure of the organ.

Levels of Structural Complexity

There are many levels of structure in the human body.

These levels include:

1. Chemical level: This level is the lowest one. The body is

formed of atoms that chemically combine to form molecules.

N.B.: The atom is the smallest particle of an element. The word

atom means indivisible. However, nowadays it is split to form

atomic energy.2.Cellular level: The molecules combine to form the cells.

N.B.: The cell is the smallest independent structural and

functional unit of the body.

3. Tissue level: The cells of the same structure and function

form tissues.

4. Organ level: Tissues of different types form organs.

5. System level: Some organs form a system.

6. Human body: Systems together form the human body. Eachof them performs a certain function, required for the health and

survival of the human being.

Atoms and molecules Cells Tissues Organs

Systems Human body



SYSTEMS OF THE BODY

i. Skeletal system: it provides the framework to the body, supports, and protects its different parts.

ii. Muscular system: It effects (causes) the movements

that occur in the different parts of the body.

**The above two systems are collectively known as a"musculoskeletal system".

iii.Nervous system: It causes the awareness and therespond of the body to the surrounding environment.

iv.Respiratory system: It allows the exchange of gases

between the body and the external air.

v. Digestive system: It allows digestion and absorption

of food, and elimination of waste products.

vi.Urinary system: It is the main excretory system of

the body.

vii. Circulatory system: It is the transport system of the

body. It transports oxygen and nutrients to the body tissues

and carbon dioxide and waste products out of them.

viii.Endocrine system: It produces hormones that control

the various body activities.

ix.Reproductive system: It keeps the life of humankind,

through reproduction of new generations.



Survival Needs of The Human Body

Each organ in the body performs its function that takes a rolein maintenance of health and survival of the whole body. Any

disease to any organ will affect the whole body.

Survival needs of the body include the following functions:

1. Intake of raw materials and elimination of waste

products:

- Intake of diet and elimination of faeces, done by the

digestive system...- Intake of oxygen and elimination of carbon dioxide, done

by the respiratory system.

- Elimination of urine, done by the urinary system.

2. Transport, done by the circulatory system, via the blood

and lymph.

3. Communication:

- Internal communication , done by the nervous and

endocrine systems.- External communication , done by the special senses

and the verbal and non-verbal communications.

4. Protection:

-External protection; done by the skin and muscle

movements.

-Internal protection; done by the immunity system.

5. Survival and Continuation of the human race done

by the reproductive systems through the process of fertilization.



Body Fluids

Water represents about 60% of the total human body weight.

This proportion is increased in young persons and decreased inold ages and in obesity.

Distribution of body fluids:

1. Intracellular fluid (ICF): It lies inside the cells and represents

about 70% of the total body fluids.

2. Extracellular fluid (ECF): It lies outside the cells, and

represents about 30% of the total body fluids. It includes the

plasma, lymph, and CSF and tissue fluid lying between the cells.

N.B. Effect of water loss on the body:

1. Loss of about 1% leads to thirst.

2. Loss of about 5% leads to dehydration.

3. Loss of about 20% leads to death.

Electrolytes

They are minute particles split from the molecules of various

salts and dissolved in water. They carry electric charges, so

called electrolytes. They include chloride (Cl ), sodium ( Na),

potassium ( K ), calcium (Ca) …etc.

Their balance in the body is essential for viability of the tissues.

In addition, they conduct electricity that is essential in

conduction of nerve impulses and muscle action.

Any slight change in the electrolytes may result in disturbance

of body functions e.g.Decrease of calcium levels results in tetany (abnormal muscle

contraction), while its increase results in muscle depression and

may end loss of contraction of the heart.



Homeostasis(Homeo=the same & stasis= remaining still)

Definition: It is the ability of the body to maintain its internal

environment constant, even with the changes of the externalenvironment.

Components of homeostasis:

Homeostasis includes three main components:

1. Chemostasis: It is the ability to maintain the balance of

electrolytes.

2. Haemostasis: It is the ability to maintain an adequate

circulation, to facilitate the passage of oxygen and nutrients to

the tissues and at the same time passage of carbon dioxide andwaste products from the tissues.

3. Thermostasis: It is the ability to maintain the body

temperature constant.

Mechanism of homeostasis:

Homeostasis is maintained by the control systems that detect

and respond to the changes in the environment. The control

system includes three main elements:

1. Receptor (or detector): that detects any change and sends it to

the control center.

2. Control center: that integrates the informations and sends its

orders to the effectors.

3. Effector: that responds to the orders to adjust the internal

environment.

Example of homeostasis: Increase of body temperature occurs

in cold weather as follows: Nerve endings in the skin (detectors)

detects low temperature and send informations to the control

center in the brain "hypothalamus". Then, the informations

reach the effectors that include the muscles that shiver, blood

vessels in the skin that narrow to warm the blood and behavioral

changes e.g. putting more clothes on the body.



CAVITIES OF THE BODY

The body has two main cavities:

I. Ventral cavity: It is subdivided into two cavities;1. Thoracic cavity ………….. . above.

2. Abdomino-pelvic cavity .…….…… below.

*The two cavities are separated from each other by

the diaphragm.

II. Dorsal cavity: It is subdivided into two cavities;1. Cranial cavity (containing the brain)

………above.2. Spinal cavity (containing the spinal cord)…

below.

*The two cavities are continuous with each other

at the foramen magnum of the skull.

Figure: Diagram, showing Cavities of the body



HUMAN SKELETON

Parts of skeleton :

Skeleton is formed of two main parts:

1. Axial skeleton : includes;

1- The skull and mandible "Bones of the head"

2- The vertebral column "Bones of the trunk"

3- The sternum and ribs "Bones of thoracic cage"

11.Appendicular Skeleton :

Bones of the appendages (limbs) and the bones of their girdle.

1- Bones of the upper limb and its shoulder girdle.

2- Bones of the lower limb and its pelvic girdle. N.B.: The skeletal system is consisted of 206 bones.

Axial Skeleton Appendicular Skeleton

Figure: Human Skeleton

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Essentials of Anatomy and Physiology (Unit 1)