ORGANIZATION OF THE BODY - diah's tought · 01/12/2010 · • The posterior body cavity is lined...

1Maria immaculata iwo, sf itb

ORGANIZATION OF THE BODYORGANIZATION OF THE BODY

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Anatomy and physiology is the study of the human body.

Anatomy is concerned with the structure of a part.For example, - The stomach is a J-shaped, pouch-like organ - The stomach wall has thick folds, which disappear as

the stomach expands to increase its capacity.

Physiology is concerned with the function of a part. For example, - the stomach temporarily stores food, secretes digestive juices, and passes on partially digested food to the small intestine.

Maria immaculata iwo, sf itb

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Anatomy and physiology are closely connected in that the structure of an organ suits its function.

For example, the stomach’s pouch-like shape and ability to expand are suitable to its function of storing food.

In addition, the microscopic structure of the stomach wall is suitable to its secretion of digestive juices.


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Organization of Body Parts● The structure of the body can be studied at

different levels of organization (Fig. 1.1).

Firstly, all substances, including body parts, are composed of chemicals made up of submicroscopic particles called atoms.

● Atoms join to form molecules, which can in turn join to form macromolecules.

For example, molecules called amino acids join to form a macromolecule called protein, which makes up the bulk of our muscles.


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● Macromolecules are found in all cells the basic units of all living things.

● Within cells are organelles tiny structures that perform cellular functions.

For example, - the organelle called the nucleus is especially concerned with cell reproduction;- another organelle, called the mitochondrion, supplies the cell with energy.


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• Tissues are the next level of organization.A tissue is composed of similar types of cells and performs a specific function.

● An organis composed of several types of tissues and performs a particular function within an organ system.


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• For example, – the stomach is an organ that is a part of the digestive system.

– It has a specific role in this system, whose overall function is to supply the body with the nutrients needed for growth and repair.

The other systems of the body also have specific functions.

All of the body systems together make up the organism—such as, a human being.


8Maria immaculata iwo, sf itb

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Anatomical terms

Figure 1.2 Directional terms. Directional terms tell us where body parts are located with reference to the body in anatomical position.

inferior

medial proximal superficialsuperior

lateral distal deep

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Anatomical position

Anatomical position: Standing erect, with face forward, arms at the sides, and palms and toes directed forward, as illustrated in Figure 1.1.


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Directional Terms● Directional terms are used to describe the location of one

body part in relation to another (Fig. 1.2):

Anterior (ventral)

means that a body part is located towardthe front. The windpipe (trachea) is anterior to the esophagus.

Posterior (dorsal)

means that a body part is located towardthe back. The heart is posterior to the rib cage.

Superior means that a body part is located above another part, or toward the head. The face is superior to the neck.

Inferior means that a body part is below another part, or toward the feet. The navel is inferior to the chin.


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Medial means that a body part is nearer than another part to an imaginary midline of the body. The bridge of the nose is medial to the eyes

Lateral means that a body part is farther away from the midline. The eyes are lateral to the nose

Proximal means that a body part is closer to the point of attachment or closer to the trunk. The elbow is proximal to the hand.

Distal means that a body part is farther from the point of attachment or farther from the trunk or torso. The hand is distal to the elbow

Superficial (external)

means that a body part is located near the surface. The skin is superficial to the muscles.

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Deep (internal)

means that the body part is located away from the surface. The intestines are deep to the spine.

Central means that a body part is situated at the center of the body or an organ. The central nervous system is located along the main axis of the body.

Peripheral means that a body part is situated away from the center of the body or an organ. The peripheral nervous system is located outside the central nervous system


14Figure 1.3 Terms for body parts and areas. a. Anterior. b. Posterior.

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Figure 1.4 Body planes and sections. The planes shown in (a), (b), and (c) are typically used as sites for sectioning the body as shown in (d), (e), and (f).

a. Sagital (median) plane

b. Frontal (coronal) plane

c. Transverse (hori-zontal) plane

d. Sagital section of pelvic cavity

e. Frontal section of thoracic cavity

f. Transverse section of head at eye level

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Figure 1.5 The two major body cavities and their subdivisions. a. Left lateral view; b. Frontal view.


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BODY CAVITIES AND MEMBRANES

● During embryonic development, the body is first divided into two internal cavities:

– the posterior (dorsal) body cavity and– the anterior (ventral) body cavity.


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Posterior (Dorsal) Body Cavity(1) The cranial cavity, enclosed by the bony cranium,

contains the brain.(2) The vertebral canal, enclosed by vertebrae,

contains the spinal cord (Fig. 1.5a)

• The posterior body cavity is lined by three membranous layers called the meninges.

• The most inner of the meninges is tightly bound to the surface of the brain and the spinal cord.

• The space between this layer and the next layer is filled with cerebrospinal fluid.

Spinal meningitis, a serious condition, is an inflammation of the meninges usually caused by an infection.


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Anterior (Ventral) Body Cavity

The large anterior body cavity is subdivided into: • the superior thoracic cavity and • the inferior abdominopelvic cavity (Fig.1.5a).

A muscular partition called the diaphragm separates the two cavities.

♦ Membranes that line these cavities are called serous membranes because they secrete a fluid (serous fluid) that has just about the same composition as serum reduces friction.


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Thoracic Cavity

• The thoracic cavity is enclosed by the rib cage, and has three portions:

• the left, • right, • medial portions

The medial portion, called the mediastinum, contains the heart, thymus gland, trachea, esophagus, and other structures (Fig. 1.5b).

The lungs are surrounded by a serous membrane called the pleura (parietal and visceral pleura, pleura cavity + pleural fluid)

contain the lungs


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Abdominopelvic Cavity has two portions:

– the superior abdominal cavity The stomach, liver, spleen, gallbladder, and most of the small and large intestines

– the inferior pelvic cavity. contains the rectum, the urinary bladder, the

internal reproductive organs, and the rest of the large intestine.

Males have an external extension of the abdominal wall, called the scrotum, where the testes are found.

Many of the organs of the abdominopelvic cavity are covered visceral peritoneum, while the wall of the abdominal cavity is lined with the parietal peritoneum (cavity: peritoneal fluid).

Peritonitis, another serious condition, is an inflammation of the peritoneum, again usually caused by an infection.


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HOMEOSTASIS● Internal conditions are not absolutely constant;

they tend to fluctuate above and below a particular value.

● the internal state of the body is often described as one of dynamic equilibrium.

● If internal conditions change to any great degree, illness results. homeostatic mechanisms medically important


A homeostatic mechanism has three components:

• A sensor, detects a change in the internal environment

• A regulatory center, activates the effectors

• An effector, reverses the change and brings conditions

back to normal again.

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25Figure 1.7 Negative feedback.

b. A mechanical example

c. A human example

a. The general pattern

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Figure 1.8 Homeostasis and body temperature regulation. Negative feedback mechanisms control body temperature so that it remains relatively stable at 37°C. These mechanisms return the temperature to normal when it fluctuates above and below this set point.

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Figure 1.9 Regulation of tissue fluid composition

Cells are surrounded by tissue fluid (blue), which is continually refreshed because oxygen and nutrient molecules constantly exit the bloodstream, and carbon dioxide and waste molecules continually enter the bloodstream.

ORGANIZATION OF THE BODY - diah's tought · 01/12/2010 · • The posterior body cavity is lined...

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