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Chapter 4: Body Structure

Introduction to Anatomy & PhysiologyS.M. Nazmul Al-Deen,Lecturer ,ART Nursing College.

Chapter 4: Body StructureChapter Overview

Levels of Organization(Cell, Tissue, Organ, System, Organism)Anatomical positionPlanes of the bodyBody cavitiesAbdominopelvic divisionsQuadrantsRegionsSpineDirectional termsPathology

This chapter presents the basic structure and functions in the body, the terms used to describe planes of the body, its cavities, the quadrants & regions of the abdominal cavity, and the divisions of the spinal column; to provide a greater understand of the general concepts of pathology (the study of the nature of diseases, their causes, development, and consequences).

Levels of OrganizationOur bodies are made up of many different levels of structure and function, some are more complex than others. Listed below, from least to most complex, are the levels of organization that make up our body systems.

1.) Cell2.) Tissue3.) Organ4.) System5.) Organism

1.) Cell: The structural and functional unit of life. The study of the body at the cellular level is called cytology. A cell consist of the following:Cell membrane: acts as a barrier that encloses the entire cell. It controls the transport of many substances to and from the cell.

Cytoplasm: a jellylike matrix of proteins, salts, water, dissolved gases, and nutrients. Inside the cytoplasm are various structures called organelles that provide socialized functions for the cell.

Nucleus: is the largest cell organelle and it is responsible for metabolism, growth, and reproduction. It carries the genetic blueprint of the organism and is found in a complex molecule called DNA that is organized into a threadlike structure called chromatin. When a cell prepares to divide, chromatin forms chromosomes, which carry thousands of genes that become our genetic blueprint.

Genes pass biological information from one generation to the next. This biological info. includes traits like hair color, body structure, and metabolic activity. All cells in the human body, except sperm cells and egg cells contain 23 pairs, or 46 chromosomes. Sperm and egg cells each have 23 unpaired chromosomes. After fertilization, each cell of the embryo then has all 46 chromosomes.

2.) Tissue: Groups of cells that perform a specialized activity. The study of tissues is called histology. More than 200 cell types make up four major tissues of the body; they are as follows:Epithelial tissue: is composed of cells arranged in a continuous sheet consisting of one or more layers.

Connective tissue: supports and connects other tissues and organs.

Muscle tissue: provides the contractile tissue of the body, which is responsible for movement.Nervous tissue: transmits electrical impulses as it relays information throughout the entire body.

This type of tissue covers surfaces of organs, lines cavities and canals, forms tubes and ducts, provides the secreting portions of glands, and makes up the epidermis of the skin.This type of tissue is made up of diverse cell types, including fibroblasts, fat cells, and blood.

This type of tissue transmits information throughout the body that allows us to move, think, taste, see and experience all functions associated with being alive.

3.) Organ: Organs are the body structures that perform specialized functions. They are composed of at least two or more tissue types.

The stomach is made up of connective tissue, muscle tissue, epithelial tissue, and nervous tissue. Muscle and connective tissue form the wall of the stomach.Epithelial and connective tissue cover the inner and outer surfaces of the stomach. Nervous tissue penetrates the epithelial lining of the stomach and its muscular wall to stimulate the release chemicals for digestion and contraction for peristalsis (the rhythmic contraction and relaxation of the walls of a tubular organ to force its contents onward).

An example:

4.) System: A body system is composed of different numbers of organs and accessory structures that have similar or related functions.

An example:

The organs of the gastrointestinal system include the esophagus, stomach, small intestine, and bowel.

The accessory structures of the GI system would be the liver, gallbladder, and pancreas. The purpose of this system is to digest food, remove and use its nutrients, and expel wastes.

5.) Organism: The highest level of organization is the organism. An organism is a complete living entity capable of independent existence. All complex organisms, including humans, are made up of several body systems that work together to sustain life.

The human body is an organism. The systems that keep us functioning are complex and must maintain a proper balance to continue to perform successfully.

There are 10 different body systems including the special senses that keep our bodies going. These systems are:1.) Integumentary system2.) Digestive system3.) Respiratory system4.) Cardiovascular system5.) Blood, Lymph, and Immune systems6.) Musculoskeletal systems7.) Genitourinary systems8.) Female Reproductive systems9.) Endocrine systems10.)Nervous systemsSpecial senses

Anatomical Position: is a body posture used to locate anatomical parts in relation to each other.Anatomical PositionThe body is erect and the eyes are looking forward. The upper limbs hang to the sides, with the palms facing forward. The lower limbs are parallel, with toes pointing straight ahead.

No matter how the body is actually positioned standing or lying down, facing forward or backward or how the limbs are actually placed, the positions and relationships of a structure are always described as if the body were in anatomical position.

Planes of the body: are identified by anatomists by the use of an imaginary flat surface called a plane. The most commonly used planes are midsagittal (median), coronal (frontal), and transverse (horizontal).

Planes of the bodyBecause of the advancement in imaging techniques; we have current imaging procedures, such as magnetic resonance imaging (MRI) and computed tomography (CT). These procedures can produce three-dimensional images on more than one plane. Making it easier to find and identify structural abnormalities in the body.

Body Cavities: Medical professionals locate structures or abnormalities by referring to the body cavity in which they are found. The body has two major cavities.1.) Dorsal (posterior), including the cranial and spinal cavities.2.) Ventral (anterior), including the thoracic and abdominopelvic cavities.Body Cavities

Abdominopelvic divisionsAbdominopelvic divisions: The abdominopelvic area of the body lies under the diaphragm. It holds the organs of digestion (abdominal area) and the organs of reproduction and excretion (pelvic area). Two anatomical methods are used to divide this area of the body for medical purposes: Quadrants and Regions.

Quadrants: Four divisions of the lower torso used to show topographical location.Regions: Primarily used to identify the location of underlying body structures and visceral organs.(p.46-text)

Quadrants: are four divisions of the lower torso used to show topographical location. They provide a means of locating specific sites for descriptive and diagnostic purposes. The divisions of quadrants are used in clinical examinations and medical reports.

Quadrants

An imaginary cross passing through the identifies the four quadrants.

Right upper Quadrant

Left upper QuadrantRight lower QuadrantLeft lower Quadrant

*Remember: Quadrants are primarily used to identify relevant sites.

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Abdominopelvic Regions: are primarily used to identify the location of underlying body structures and visceral organs.Regions

An example: the stomach is located in the left hypochondriac and epigastric region.

Right hypochondriac regionRight lumbar regionRight inguinal (iliac) region

Epigastric region

Umbilical regionHypogastric region

Left hypochondriac regionLeft inguinal (iliac) regionLeft lumbar region

Another example: the appendix is located in the hypogastric region of the body.

Spine: The spine is divided into sections corresponding to the vertebrae located in the spinal column. These divisions are:Cervical spine: 7 vertebrae (C1C7)Thoracic spine: 12 vertebrae (T1T12)Lumbar spine: 5 vertebrae (L1L5)Sacrum: 5 (fused) vertebrae (S1S5)Coccyx: 4 (35) (fused) vertebrae (Tailbone)

Spine