INTRODUCTION OF HUMAN BODY AND CELLULAR ORGANIZATION

INTRODUCTION OF HUMAN BODY

Detail study of human body is includes anotomy and physiology of human body and cellular composition.

Anotomy is a study of structure and parts of each and every part of human body.

Physiology is a study of functions of human body

1.1 Anatomy and Physiology Defined

 1. Anatomy is the science of body structures and the relationships among structures; physiology is the

science of body functions.

 2. Dissection is the careful cutting apart of body structures to study their relationships.

 3. Some branches of anatomy are embryology, developmental biology, cell biology, histology, gross

anatomy, systemic anatomy, regional anatomy, surface anatomy, radiographic anatomy, and pathological

anatomy (see Table 1.1).

 4. Some branches of physiology are neurophysiology, endocrinology, cardiovascular physiology, immunol-

ogy, respiratory physiology, renal physiology, exercise physiology, and pathophysiology (see Table 1.1).

1.2 Levels of Structural Organization and Body Systems

 1. The human body consists of six levels of structural organization: chemical, cellular, tissue, organ, system,

and organismal.

 2. Cells are the basic structural and functional living units of an organism and are the smallest living units

in the human body.

 3. Tissues are groups of cells and the materials surrounding them that work together to perform a particular

function.

 4. Organs are composed of two or more different types of tissues; they have specific functions and usually

have recognizable shapes.

 5. Systems consist of related organs that have a common function.

 6. An organism is any living individual.

 7. Table 1.2 introduces the 11 systems of the human organism: the integumentary, skeletal, muscular, nervous,

endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems.

1.3 Characteristics of the Living Human Organism

 1. All organisms carry on certain processes that distinguish them from nonliving things.

 2. Among the life processes in humans are metabolism, responsiveness, movement, growth, differentia-

tion, and reproduction.

1.4 Homeostasis

 1. Homeostasis is a condition of equilibrium in the body’s internal environment produced by the interplay

of all of the body’s regulatory processes.

 2. Body fluids are dilute, watery solutions. Intracellular fluid (ICF) is inside cells, and extracellular fluid (ECF)

is outside cells. Plasma is the ECF within blood vessels. Interstitial fluid is the ECF that fills spaces between

tissue cells; because it surrounds all body cells, interstitial fluid is called the body’s internal environment.

 3. Disruptions of homeostasis come from external and internal stimuli and psychological stresses. When

disruption of homeostasis is mild and temporary, responses of body cells quickly restore balance in the

internal environment. If disruption is extreme, regulation of homeostasis may fail.

 4. Most often, the nervous and endocrine systems acting together or separately regulate homeostasis. The

nervous system detects body changes and sends nerve impulses to counteract changes in controlled

conditions. The endocrine system regulates homeostasis by secreting hormones.

 5. Feedback systems include three components: (1) Receptors monitor changes in a controlled condition

and send input to a control center (afferent pathway). (2) The control center sets the value (set point) at

which a controlled condition should be maintained, evaluates the input it receives from receptors (effer-

ent pathway), and generates output commands when they are needed. (3) Effectors receive output from

the control center and produce a response (effect) that alters the controlled condition.

 6. If a response reverses the original stimulus, the system is operating by negative feedback. If a response

enhances the original stimulus, the system is operating by positive feedback.

 7. One example of negative feedback is the regulation of blood pressure. If a stimulus causes blood pres-

sure (controlled condition) to rise, baroreceptors (pressure-sensitive nerve cells, the receptors) in blood

vessels send impulses (input) to the brain (control center). The brain sends impulses (output) to the heart

(effector). As a result, heart rate decreases (response) and blood pressure decreases to normal (restora-

tion of homeostasis).

 8. One example of positive feedback occurs during the birth of a baby. When labor begins, the cervix of

the uterus is stretched (stimulus), and stretch-sensitive nerve cells in the cervix (receptors) send nerve

impulses (input) to the brain (control center). The brain responds by releasing oxytocin (output), which

stimulates the uterus (effector) to contract more forcefully (response). Movement of the fetus further

stretches the cervix, more oxytocin is released, and even more forceful contractions occur. The cycle is

broken with the birth of the baby.

 9. Disruptions of homeostasis—homeostatic imbalances—can lead to disorders, diseases, and even death.

A disorder is a general term for any abnormality of structure or function. A disease is an illness with a

definite set of signs and symptoms.

 10. Symptoms are subjective changes in body functions that are not apparent to an observer; signs are objec-

tive changes that can be observed and measured.

1.5 Basic Anatomical Terminology

 1. Descriptions of any region of the body assume the body is in the anatomical position, in which the sub-

ject stands erect facing the observer, with the head level and the eyes facing directly forward. The feet

are flat on the floor and directed forward, and the upper limbs are at the sides, with the palms turned

forward. A body lying facedown is prone; a body lying faceup is supine.

 2. Regional names are terms given to specific regions of the body. The principal regions are the head, neck,

trunk, upper limbs, and lower limbs. Within the regions, specific body parts have anatomical names and

corresponding common names. Examples are thoracic (chest), nasal (nose), and carpal (wrist).

 3. Directional terms indicate the relationship of one part of the body to another. Exhibit 1.A summarizes

commonly used directional terms.

 4. Planes are imaginary flat surfaces that are used to divide the body or organs to visualize interior struc-

tures. A midsagittal plane divides the body or an organ into equal right and left sides. A parasagittal

plane divides the body or an organ into unequal right and left sides. A frontal plane divides the body

or an organ into anterior and posterior portions. A transverse plane divides the body or an organ into

superior and inferior portions. An oblique plane passes through the body or an organ at an oblique angle.

 5. Sections are cuts of the body or its organs made along a plane. They are named according to the plane

along which the cut is made and include transverse, frontal, and sagittal sections.

 6. Figure 1.9 summarizes body cavities and their membranes. Body cavities are spaces in the body that

help protect, separate, and support internal organs. The cranial cavity contains the brain, and the verte-

bral canal contains the spinal cord. The meninges are protective tissues that line the cranial cavity and

vertebral canal. The diaphragm separates the thoracic cavity from the abdominopelvic cavity. Viscera

are organs within the thoracic and abdominopelvic cavities. A serous membrane lines the wall of the

cavity and adheres to the viscera.

7. The thoracic cavity is subdivided into three smaller cavities: a pericardial cavity, which contains the heart,

and two pleural cavities, each of which contains a lung. The central part of the thoracic cavity is an anatomi-

cal region called the mediastinum. It is located between the pleural cavities, extending from the sternum to

the vertebral column and from the first rib to the diaphragm. It contains all thoracic viscera except the lungs.

 8. The abdominopelvic cavity is divided into a superior abdominal and an inferior pelvic cavity. Viscera

of the abdominal cavity include the stomach, spleen, liver, gallbladder, small intestine, and most of the

large intestine. Viscera of the pelvic cavity include the urinary bladder, portions of the large intestine,

and internal organs of the reproductive system.

 9. Serous membranes line the walls of the thoracic and abdominal cavities and cover the organs within

them. They include the pleura, associated with the lungs; the pericardium, associated with the heart; and

the peritoneum, associated with the abdominal cavity.

 10. To describe the location of organs more easily, the abdominopelvic cavity is divided into nine regions:

right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right inguinal

(iliac), hypogastric (pubic), and left inguinal (iliac). To locate the site of an abdominopelvic abnormality

in clinical studies, the abdominopelvic cavity is divided into quadrants: right upper quadrant (RUQ), left

upper quadrant (LUQ), right lower quadrant (RLQ), and left lower quadrant (LLQ).

1.6 Medical Imaging

 1. Medical imaging refers to techniques and procedures used to create images of the human body. They allow

visualization of internal structures to diagnose abnormal anatomy and deviations from normal physiology.

 2. Table 1.3 summarizes and illustrates several medical imaging techniques.