[Chapter 1] The Human Body: An Orientation Flashcards

Question

**[1.2] The body's organization ranges from atoms to the entire organism** _The 11 Organ Systems of the Body: Urinary_

Answer 1

Every living organism must **maintain its boundaries** so that its internal environment (its inside) remains distinct from the external environment (its outside). * In single-celled organisms: the external boundary is a limiting membrane that encloses its contents and lets in needed substances while restricting entry of potentially damaging or unnecessary substances * Similarly, all body cells are surrounded by a selectively permeable membrane * Additionally, the body as a whole is enclosed and protected by the integumentary system, or skin. This system protects our internal organs from drying out (a fatal change), bacteria, and the damaging effects of heat, sunlght, and an unbelievable number of chemicals in the external environment

Answer 2

**Movement** includes the activities promoted by the muscular system, such as propelling ourselves from one place to another The skeletal system provides the bony framework that the muscles pull on as they work Movement also occurs when substances such as blood, foodstuffs, and urine are propelled through internal organs of the cardiovascular, digestive, and urinary systems, respectivley On the cellular level, the muscle cell's ability to move by shortening is more precisely called **contractility**

Answer 3

**Responsiveness**, or **excitability**, is the ability to sense changes (stimuli) in the environment and then respond to them Because nerve cells are highly excitable and communicate rapidly with each other via electrical impulses, the nervous system is most involved with responsiveness However, all body cells are excitable to some extent

Answer 4

**Digestion** is the breaking down of ingested foodstuffs to simple molecules that can be absorbed into the blood. The nutrient-rich blood is then distributed to all body cells by the cardiovascular system. In a simple, one-celled organism such as an amoeba, the cell itself is the "digestion factory," but in the multicellular human body, the digestive system performs this function for the entire body

Answer 5

**Metabolism** is a broad term that includes all chemical reactions that occur within body cells. * It includes breaking down substances into simpler building blocks (the process of *catabolism*) * synthesizing more complex cellular structures from simpler substances (*anabolism*) * using nutrients and oxygen to produce (via *cellular respiration*) ATP; the energy-rich molecules that power cellular activities Metabolism depends on the digestive and respiratory systems to make nutrients and oxygen available to the blood, and on the cardiovascular system to distribute them throughout the body Metabolism is regulated largely by hormones secreted by endocrine system glands

Answer 6

**Excretion** is the process of removing wastes, or *excreta*, from the body. If the body is to operate as we expect it to, it must get rid of nonuseful substances produced during digestion and metabolism Several organ systems participate in excretion. For example, the digestive system rids the body of indigestible food residues in feces, and the urinary system disposes of nitrogen-containing metabolic wastes, such as urea, in urine.

Answer 7

**Reproduction** occurs at the cellular and the organismal level (major task) * In cellular reproduction, the original cell divides, producing two identical daughter cells that may then be used for body growth or repair * Reproduction of the human organism. When a sperm unites with an egg, a fertilized egg forms and develops into a baby within the mother's body The reproductive system is directly responsible for producing offspring, but its function is exquisitely regulated by hormones of the endocrine system

Answer 8

**Growth** is an increase in size of a body part or the organism as a whole It is usually accompanied by increasing the number of cells. However, individual cells also increase in size when not dividing For true growth to occur, constructive activities must occur at a faster rate than destructive ones

Answer 9

**Nutrients**, taken via the diet, contain the chemical substances used for energy and cell building. Most plant-derived foods are rich in carbohydrates, vitamins, and minerals, whereas most animal foods are richer in proteins and fats * Carbohydrates are the major energy fuel for body cells * Proteins, and to a lesser extent fats, are essential for building cell structures * Fats also provide a reserve of energy-rich fuel * Selected minerals and vitamins are required for the chemical reactions that go on in cells and for oxygen transport in the blood * The mineral calcium helps to make bones hard and is required for blood clotting

Answer 10

All the nutrients in the world are useless unless **oxygen** is also available. Because the chemical reactions that release energy from foods are *oxidative* reactions that require oxygen, human cells can survive for only a few minutes without oxygen. Approximately 20% of the air we breathe is oxygen The cooperative efforts of the respiratory and cardiovascular systems make oxygen available to the blood and body cells

Answer 11

**Water** accounts for 50-60% of our body weight and is the single most abundant chemical substance in the body. It provides the watery environment necessary for chemical reactions and the fluid base for body secretions and excretions We obtain water chiefly from ingested foods or liquids We lose it from the body by evaporation from the lungs and skin and in body excretions

Answer 12

If chemical reactions are to continue at life-sustaining rates, **normal body temperature** must be maintained At either extreme (too low or too high of a temperature), death occurs The activity of the muscular system generates most body heat

Answer 13

**Atmospheric pressure** is the force that air exerts on the surface of the body Breathing and gas exchange in the lungs depend on *appropriate* atmospheric pressure At high altitudes, where atmospheric pressure is lower and the air is thin, gas exchange may be inadequate to support cellular metabolism

Answer 14

The ultimate goal of all body systems is to maintian life. However, life is very fragile and requires several factors. These factors, which we will call **survival needs**, include nutrients (food), oxygen, water, and appropriate temperature and atmospheric pressure. The mere presence of these survival factors is not sufficient to sustain life. They must be present in the proper amounts. Too much and too little may be equally harmful. For example, oxgyen is essential, but excessive amounts are toxic to body cells.

Answer 15

**Homeostasis** is the body's ability to maintain relatively stable internal conditions even though the outside world changes continuously It is a *dynamic* state of equilibrium

Answer 16

Communication within the body is essential for homeostasis and is accomplished chiefly by the nervous and endocrine systems, which use neural electrical impulses for bloodborne hormones, respectively, as information carriers.

Answer 17

Regardless of the factor or event being regulated - the **variable** - all homeostatic control mechanisms are processes involvong at least three components that work together

Answer 18

The first component, the **receptor**, is some type of sensor that monitors the environment and responds to changes, called *stimuli*, by sending information (input) to the second component, the *control center* Input flows from the receptor to the control center along the *afferent pathway*

Answer 19

The **control center** determines the *set point*, which is the level or range at which a variable is to be maintained It also analyzes the input it receives and determines the appropriate response Information (output) then flows from the control center to the third component, the *effector*, along the *efferent pathway*

Answer 20

The **effector** provides the means for the control center's respsonse (output) to the stimulus The results of the response then *feed back* to influence the effect of the stimulus, either reducing it so that the whole control process is shut off, or enhancing it so that the whole process continues at an even faster rate

Answer 21

Most homeostatic control mechanisms are **negative feedback mechanisms**. In these systems, the output shuts off the original effect of the stimulus or reduces its intensity These mechanisms casue the variable to change in a direction *opposite* to that of the initial change, returning it to its "ideal" value The endocrine system is equally important in maintaining homeostasis. A good example of a hormonal negative feedback mechanism is the control of blood sugar (glucose) by insulin. As blood sugar rises, receptors in the body sense this change, and the pancreas (the control center) secretes insulin into the blood. This change in turn prompts body cells to absorb more glucose, removing it from the bloodstream. As blood sugar falls, the stimulus for insulin release ends Other negative feedback mechanisms regulate heart rate, blood pressure, the rate and depth of breathing, and blood levels of oxygen, carbon dioxide, and minerals

Answer 22

In **positive feedback mechanisms**, the result or response enhances the original stimulus so that the response is accelerated This feedback mechanism is "positive" because the change that results proceeds in the *same* direction as the initial change, causing the variable to deviate further and further from its original value or range In contrast to negative feedback controls, which maintain some physiological function or keep blood chemicals within narrow ranges, positive feedback mechanisms usually control infrequent events that do not require continuous adjustments. Typically, they set off a series of events that may be self-perpetuating and that, once initiated, have an amplifying or waterfalle effect. Because of these characteristics, positive feedback mechanisms are often referred to as *cascades* Two familiar examples are the enhancement of labor contractions during birth and blood clotting

Answer 23

Homeostasis is so important that most disease can be regarded as a result of its disturbance, a condition called **homeostatic imbalance** Homeostatic imbalance occurs from: * aging * when negative feedback mechanisms are overwhelmed and destructive positive feedback mechanisms take over (ex. heart failure)

Answer 24

The anatomical reference point is a standard body position called the **anatomical position**. This position resembles "standing at attention," except that the palms face forward and the thumbs point away from the body It is important to understand the anatomical position because most of the directional terms in this book refer to the body *as if it were in this position, regardless of its actual position* The terms "right" and "left" refer to those sides of the person or the cadaver being viewed- not those of the observer

Answer 25

**Directional terms** allow us to explain where one body structure is in relation to another Using anatomical terms saves words and is less ambiguous

Answer 26

The two fundamental divisions of our body are its *axial* and *appendicular* parts * the **axial part**, which makes up the main *axis* of our body, includes the head, neck, and trunk * the **appendicular part** consists of the *appendages*, or *limbs,* which are attached to the body's axis **Regional terms** are used to designate specific areas within these major body divisions and are indicated in Figure 1.7

Answer 27

For anatomical studies, the body is often cut, or *sectioned*, along a flat surface called a *plane* The most frequently used body planes are: * *sagittal* * *frontal* * *transverse* A section is named for the plane along which it is cut; thus, a cut along a sagittal plane produces a saggital section

Answer 28

A **sagittal plane** is a vertical plane that divides the body into right and left parts * A sagittal plane that lies exactly in the midline is the **median plane**, or **midsagittal plane** * All other sagittal planes, offset from the midline, are **parasagittal planes**

Answer 29

**Frontal planes** (also called **coronal planes**), like sagittal planes, lie vertically. Frontal planes, however, divide the body into anterior and posterior parts

Answer 30

A **transverse**, or **horizontal**, **plane** runs horizontally from right to left, dividing the body into superior and inferior parts Of course, many different transverse planes exist, at every possible level from head to foot A transverse section is also called a **cross section**

Answer 31

**Oblique sections** are cuts made diagonally between the horizontal and vertical planes. Because oblique sections are often confusing and difficult to interpret, they are seldom used

Answer 32

Anatomy and physiology textbooks typically describe two sets of internal body cavities called the dorsal and ventral body cavities These cavities are closed to the outside and provide different degrees of protection to the organs within them Because these two cavities differ in their mode of embryonic development and their lining membranes, the dorsal body cavity is not recognized as such in many anatomical references. However, the idea of two sets of internal body cavities is a useful learning concept and we use it here

Answer 33

The **dorsal body cavity**, which protects the fragile nervous system organs, has two subdivisions: * The **cranial cavity**, in the skull, encases the brain * The **vertebral**, or **spinal**, **cavity**, which runs within the bony vertebral column, encloses the delicate spinal cord. The spinal cord is essentially a continuation of the brain, and the cranial and spinal cavities are continuous with one another Both the brain and the spinal cord are covered by membranes called meninges

Answer 34

The more anterior and larger of the closed body cavities is the **ventral body cavity**. Like the dorsal cavity, it has two major subdivisions: * The *thoracic cavity* * The *abdominal cavity* The ventral body cavity houses internal organs collectively called the **viscera**, or visceral organs

Answer 35

The superior subdivision, the **thoracic cavity**, is surrounded by the ribs and muscles of the chest. The thoracic cavity is further subdivided into lateral **pleural cavities**, each enveloping a lung, and the medial **mediastinum**. The mediastinum contains the **pericardial cavity**, which encloses the heart, and it also surrounds the remaining thoracic organs (esophagus, trachea, and others)

Answer 36

The thoracic cavity is separated from the more inferior **abdominopelvic cavity** by the diaphragm, a dome-shaped muscle important in breathing The abdominopelvic cavity, as the name suggests, has two parts. However, these regions are not physically separated by a muscular or membrane wall. * Its superior portion, the **abdominal cavity**, contains the stomach, intestines, spleen, liver, and other organs * The inferior part, the **pelvic cavity**, lies in the bony pelvis and contains the urinary bladder, some reproductive organs, and the rectum The abdominal and pelvic cavities are not aligned with each other. Instead, the bowl-shaped pelvis tips away from the perpendicular as shown in Figure 1.9a.

Answer 37

The walls of the ventral body cavity and the outer surfaces of the organs it contains are covered by a thin, double-layered membrane, the **serosa**, or **serous membrane**. The part of the membrane lining the cavity waslls is called the **parietal serosa**. It folds in on itself to form the **visceral serosa**, covering the organs in the cavity. In the body, the serious membranes are separated not by air but by a thin layer of lubricating fluid, called **serous fluid**, which is secreted by both membranes. Although there is a potential space between the two membranes, the barely present, slitlike cavity is filled with serous fluid Serous fluid allows organs to move without friction and is especially important for mobile organs such as the pumping heart and the churning stomach The serous membranes are named for the specific cavity and organs with which they are associated. For example, as shown in Figure 1.10b, the *parietal pericardium* lines the pericardial cavity and folds back as the *visceral pericardium*, which covers the heart. Likewise, the *parietal pleurae* line the walls of the thoracic cavity, and the *visceral pleurae* cover the lungs. The *perietal peritoneum* is associated with the walls of the abdominopelvic cavity, while the *visceral peritoneum* covers most of the organs within that cavity.

Answer 38

A simple scheme to locate the abdominopelvic cavity organs in which a tranverse and a median plane pass through the umbilicus at right angles and results in four quadrants which are named according to their positions: * The **right upper quadrant (RUQ)** * The **left upper quadrant (LUQ)** * The **right lower quadrant (RLQ)** * The **left lower quadrant (LLQ)**

Answer 39

Another division method, used primarily by anatomists, uses two transverse and two parasagittal planes. These planes, positioned like a tic-tac-toe grid on the abdomen, divide the cavity into nine regions * The **umbilical region** is the centermost region deep to and surrounding the umbilicus (navel) * The **epigastric region** is located superior to the umbilical region * The **hypogastric (pubic) region** is located inferior to the umbilical region * The **right** and **left iliac**, or **inguinal**, **regions** are located lateral to the hypogastric region * The **right** and **left lumbar regions** lie lateral to the umbilical region * The **right** and **left hypochondriac regions** lie lateral to the epigastric region and deep to the ribs

Answer 40

In addition to the large closed body cavities, there are several smaller body cavities. Most of these are in the head and most open to the body exterior Figure 1.7 provides the terms that will help you locate all but the last two cavities mentioned here

Answer 41

The oral cavity, commonly called the mouth, contains the teeth and tongue. This cavity is part of and continuous with the cavity of the digestive organs, which opens to the body exterior at the anus

Answer 42

Located within and posterior to the nose, the nasal cavity is part of the respiratory system passageways

Answer 43

The orbital cavities (orbits) in the skull house the eyes and present them in an anterior position

Answer 44

The middle ear cavities in the skull lie just medial to the eardrums. These cavities contain tiny bones that transmit sound vibrations to the hearing receptors in the inner ears

Answer 45

Synovial cavities are joint cavities. They are enclosed within fibrous capsules that surround freely movable joints of the body (such as the elbo and knee joints). Like the serous membranes, membranes lining synovial cavities secrete a lubricating fluid that reduces friction as the bones move across one another

[Chapter 1] The Human Body: An Orientation Flashcards

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