Introductory Anatomy and Physiology: Text & Lab Manual
Lead Author(s): Karen M. Chooljian, M.S.
Student Price: Contact us to learn more
Interactive text and complete lab manual with active learning assignments and embedded questions for immediate student and instructor feedback.
Introduction to Anatomy and Physiology
You are sitting in front of a computer to read this text, probably because you have to take a course in anatomy and physiology to fulfill a requirement for your major, but possibly because you are interested in your body and how it works. Maybe both! Perhaps you have listened to medical professionals speaking and could only understand one word in an entire speech, and realized that you need to be able to communicate to them in more articulate words than, "Huh?" Get comfortable in that chair and be prepared: learning anatomy and physiology is like learning an entirely new language!
- Define anatomy and physiology, integrating and applying that information to the physical exam and common medical tests
- Identify the structural and functional organization of the human body, explore the relationship of this organization to the basic functions of the human body
- Identify the eleven organ systems
- Define homeostasis and identify homeostatic mechanisms including components of a feedback system and positive and negative feedback
- Identify and define the anatomical position, directional terms, body planes and sections, the major regions of the body, the body cavities and the organs they contain, and the regions and quadrants of the abdominopelvic cavity
1.1 Overview of Human Anatomy and Physiology
Anatomy is the science of studying structures in the body and the relationships between them. In health care, the first observations of a patient or client are based on superficial anatomy, or the visual and/or tactile study of the external features of the body. For example, it is important to determine superficial landmarks to allow the placement of a stethoscope for auscultation of the heart sounds. Superficial anatomy is a branch of gross anatomy, the study of structures that can be seen without dissection or a microscope (i.e., with the naked eye).
Cardiology, radiology, physical therapy, and other health care fields utilize systemic or regional anatomy to treat diseases or promote health in those disciplines. Relationships between the body's organs can be visualized by imaging techniques or dissection, which is studied by specialists in radiographic or pathological anatomy. In addition, health care professionals use cytology and histology to study anatomy at the microscopic level. Developmental anatomy and embryology study the anatomy of a developing human.
Physiology is the study of the interactions between the physical and biochemical functions that keep the human body alive. There are subdivisions in physiology that are equivalent to those of anatomy e.g., cellular physiology (cytology and histology). In addition, there are entire health care fields devoted to systemic or regional anatomy such as exercise physiology, neurophysiology, cardiovascular physiology, reproductive physiology, and others.
Anatomy and Physiology Combined
There is no structure without a function in the human body. The reverse is also true: no functions can take place in the body unless there are structures for them to use. Anatomy, the study of structure or form, is inextricably linked to physiology, the study of the function of these structures.
The Physical Exam
A perfect example from the real world that illustrates the importance of understanding the relationships between structure and function is the physical exam given to a patient in a physician's office. It is an extremely important tool for understanding the health of an individual. When a patient complains of feeling ill, they relate their symptoms to the doctor, who then looks for signs of a disease. Note that symptoms are difficult to quantify, but signs such as temperature, blood pressure, and other measurements can be taken and compared to normal human ranges to assess the health of the patient. There are five components to a physical exam:
- Inquiry: taking the patient's medical history and symptoms of the current illness.
- Inspection: careful observation of body proportion, posture, gait, color of skin and eyes, and even speech patterns.
- Palpation: finding the location of anatomical landmarks, feeling the presence and texture of masses beneath the skin, taking the pulse, and locating painful areas.
- Percussion: tapping the chest and abdomen and listening to the sound that results to determine whether there is a solid mass or air under the area being tapped.
- Auscultation: listening to the internal sounds of the body using a stethoscope.
In the course of the physical exam four vital signs, or measurements of the body's most basic functions, are taken.
- Body temperature. "Normal" is 97.8°F or 36.5°C, but varies with time of day, gender, age, recent activity, whether the person has recently eaten, and other factors.
- Pulse rate. This is the measurement of how many times the heart beats per minute, with "normal" being from 60 to 100 beats per minute varying with age, gender, and other factors).
- Respiratory rate. The number of breaths taken in one minute, with "normal" ranging from 12 to 16 breaths per minute. Several factors influence both rate and depth of breathing.
- Blood pressure. The force that blood exerts against the walls of arteries. This is recorded with two numbers, with the first (systolic pressure) measuring the pressure resulting from the left ventricle's contraction (systole) and the second (diastolic pressure) measuring the elastic recoil of the large arteries.
There are other signs that can be used, such as weight, height, and pain assessment. Weight and height are easy to quantify and may have effects (especially weight) on the health of an individual. Pain is hard to measure, but a numeric scale of 0 to 10 is used to help quantify the individual's symptoms, with 0 being no pain at all and 10 being severe.
Numerous diagnostic exams are performed routinely on patients to assess structure and function. Below is a partial list of these tests, many of which will become clearer as you learn the terminology used in the study of anatomy and physiology.
Endoscopy (bronchoscopy, laparoscopy, cystoscopy, esophagoscopy, gastroscopy, colonoscopy, arthroscopy): a fiber-optic tube is inserted into the body, allowing direct visualization and biopsy of the organs and tissues.
Cytology: studying cells or tissue samples from the body (blood, urine, Pap smears, biopsies, etc.) can give information on the health of the body.
Medical Imaging Tests
X-Ray (standard and contrast; mammogram): a medical imaging technique using electromagnetic radiation of high energy and short wavelength that can travel through the tissues of the body but is absorbed by some of them. Because hollow or fluid-filled organs do not absorb X-rays well, a contrast medium or dye is injected or swallowed, allowing the structure of interest to show up as white on the regular X-ray image. Because X-rays are known carcinogens, this type of X-ray is rapidly being replaced by CT scans, MRIs, and ultrasounds (see below). In addition, radiation therapy (using much higher doses of X-rays than are used in imaging tests) is focused on cancer cells and results in their death. Unfortunately, this treatment can lead to mutations in the DNA of healthy cells in the area being treated, so the benefit of the treatment needs to outweigh the risks.
Angiography: a type of X-ray imaging test that uses a radio-opaque dye injected into the blood stream to visualize the blood flow in an artery or vein. The most common studies are the coronary arteries, pulmonary arteries, the brain, head and neck, and aorta.
Nuclear scan: small amounts of radioactive material are injected into the body or swallowed. The material usually concentrates in the organ involved and is then imaged. This test is used to detect tumors, infections, and degenerative disorders like osteoporosis.
CAT scan: specific areas of the body are given a large series of two-dimensional X-rays, each of which are taken along a different axis of the body. The cross-sectional “slices” of the body obtained in this way are called tomographic images, which are then combined into a three-dimensional image by a computer. CT thus stands for Computed Tomography (CAT for Computerized Axial Tomography), and this imaging technique provides a much more detailed image than regular X-rays.
PET scan: a type of CT scan that uses Positron Emission Tomography.The radioactive tracer is tagged to glucose, injected, and then travels to cells that are using glucose for energy.These areas are bright on the resulting scan and the computer adds color to show which portions of the body are taking up more glucose.The areas that are not using the glucose will show up in darker colors on the images.PET scans are used to detect active cells (or cancer cells) and are both an anatomical and a physiological study.They can be used to diagnose cancer, epilepsy, Alzheimer’s disease, heart disease, and other health conditions because they reveal both structure and function.
MRI: Magnetic Resonance Imagery. Again this is an imaging technique that allows study of both the anatomy and physiology of the body, but it does not involve X-rays or ionizing radiation. Powerful, rotating magnets set up a magnetic field that causes the hydrogen atoms in the body to realign. Hydrogen, abundant in the body because of water and fat, has an atomic nucleus that can emit radio waves when placed in an external magnetic field. As the magnetic field is applied at the appropriate resonance frequency, the excited hydrogen atoms emit a radio signal that is detected by a receiving coil. The atoms return to the equilibrium state (unexcited state) but do so at different rates depending on the tissue of the body where they are located. Images of the tissues are exquisitely detailed.
Ultrasound: also known as sonography, this imaging technique uses high-frequency sound waves that “bounce back” when they hit dense material. This is a useful, safe technique for examining the delicate tissues of an embryo or fetus without exposing it to ionizing radiation.This procedure is commonly used to examine internal organs and other soft tissues as well as providing information on tumors and cysts. Echocardiograms are Doppler ultrasounds that can help determine the functional health of the heart and blood vessels.
Tests of Electrical Activity (pysiological)
Certain cells of the body, neurons and muscles (skeletal, cardiac, and smooth) can transmit electrochemical impulses. In the human body, an electrical charge is transmitted by movement of ions crossing cell membranes rather than movement or interaction of electrons. This conductance is based on opening and closing ion channels and the resulting changes in the membrane potential, discussed in subsequent chapters.
Electrocardiograph (ECG): a measure of the electrical activity of the heart. This exam gives information about the rhythm and rate of the resting heartbeat.
Electroencephalograph (EEG): a measure of the electrical activity of the brain that results from voltage changes in neurons. These currents are measured over time and create oscillations called "brain waves" that can be characterized by their frequency and amplitude.
Electromyography (EMG): a measure of the electrical activity of a muscle and can be used to diagnose the health of the muscle and the motor neuron that controls it.
the study of the structure of organs in the body
the study of the function of cells in the body
the study of organs making up the systems of the body
the study of the electrical signals of neurons
Both A and B are correct
Both A and C are correct
Physiology is the study of _ in the human body.
Which of the following is NOT a vital sign?
Match the test on the left with the appropriate field of study on the right.
physiology and anatomy
1.2 Biological Organization
Levels of Organization
As stated above, all structures in the body have a function and there is no function without a structure for it. This is true all the way down to the level of atoms! Biological organization refers to the hierarchy of complexity in structures and systems, and specifically in this course refers to the increase in organization extending from atoms to molecules to organelles (sub-cellular levels), cells (cellular level), tissues, organs, organ systems and the human organism (super-cellular levels). In this course we will not study the ecological levels of organization, but will limit our study to the organizational hierarchy as illustrated in Table 1.1: the human organism. To understand the hierarchy, you need to understand the basis for the levels of structural organization and what those levels mean in terms of function.
Table 1.1 Levels of Organization
OARRA: Organization, Acquisition, Response, Reproduction, Adaptation
All living things have these fundamental functional characteristics in common: organization, acquisition of materials and energy, response to environmental changes, reproduction (both asexual and sexual are found in the human species), and adaptation. Though adaptation usually refers to evolutionary changes in biological texts, we will be referring to the adaptations that humans use to maintain homeostasis.
Organization: living organisms (and humans) are structured. This starts at the atomic level with the three-dimensional structure of an atom, which influences the shape (and thus the function) of the molecules and biomolecular complexes made up of these individual atoms. Organelles in a human cell serve as functional assemblies of these biomolecules and provide a structure for the chemical reactions and interactions between them. In turn these organelles are arranged within the human cell. Similar cells express different portions of the genotype to produce internal metabolic pathways and extracellular matrices. These structurally and functionally similar groups of cells work together in the body to form the tissues. Tissues are further organized into organs, and groups of organs working together then function as organ systems, which in turn ensure the survival of the human organism. Note that each of these organizational levels represents a higher degree of structure, complexity and function as seen in Figure 1.14.
The key to understanding the function of these organizational levels is that homeostasis in the human body begins at the sub-cellular level and with the structures that allow the segregation of the body’s chemical reactions. These reactions, in turn, provide the mechanism for the six life processes of humans as they relate to OARRA.
Metabolism: acquisition of materials and energy. The sum of all the chemical processes in the body, including anabolism and catabolism.
Response: the ability to sense and respond to changes in the external environment.
Movement: motion of the structures in the body, across the continuum of levels from organelles to the entire organism.
Growth: an increase in size and complexity of cells, cellular growth, or an increase in the number of cells (or all of the above).
Differentiation: the changes in cellular development whereby unspecialized cells change their structure and function (e.g., liver cells are different from skin cells)
Reproduction: the formation of new cells for growth, repair, and replacement or the formation of gametes to create a new individual.
Three-dimensional shape begins at the atomic level of organization.
Which of the following represents a structure (organization) that allows the normal function (life processes) of the human body?
A, B, and C only
D and E only
A mitochondrion making ATP in one of your intestinal cells represents the (subcellular/cellular/supercellular) level of organization.
Which of the following life processes is being illustrated by you eating your lunch?
Both Metabolism and Movement
Metabolism, Movement, and Response
1.3 Organ Systems
As you may have noticed, this text is also organized around the Organ Systems level! There are many ways to study anatomy and physiology, but the table of contents gives you a good idea about the easiest way to study the extremely complex human body. We will study the structures and functions of the eleven principal systems summarized in Table 1.2. For each system, we will determine which organs make up the system, how each organ is structurally adapted to perform its function, and how the tissues and cells of the organ are structurally and functionally different to allow the specialized functions. The key point to remember is that the relationship between structure and function occurs at each level of organization.
Table 1.2 Organ Systems
The human organ system which regulates body activities through the action of hormones is the (_) system.
Which of the following organ systems would be the best association with Metabolism?
Which organ system is represented by this illustration?
As we study, it is important for you to remember that no organ system acts alone. They are all interdependent. This leads us to a discussion of homeostasis, or how the body's systems contribute to survival of the organism.
Definition of Homeostasis
The Biology Online Dictionary defines homeostasis as “the tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, so as to stabilize health and functioning, regardless of the outside changing conditions.”
Homeostasis is a central principle in physiology. It is the ability of an organism to maintain a constant internal environment even though there are changes in the external environment. The concept of homeostasis allows us to understand complex regulatory mechanisms in the body and gives us a normal framework from which we can analyze pathophysiology. Maintaining homeostasis usually involves more than one organ system. For example, cardiac output (stroke volume and beats per minute) and blood pressure must be properly controlled or organ systems will begin to malfunction. Electrical signals from the nervous system or hormonal signals from the endocrine system provide a communication link so that the heart provides adequate blood to the organs that are actively using it. However, limitations exist to these regulatory mechanisms.
Homeostatic Control. The classic example of homeostatic control is the thermostat in a room. The event or factor being controlled is the variable X (room temperature) which is maintained within a narrow limit around a set point (level or range, the temperature at which you have set the thermostat). A control or integrating center (the thermostat) analyzes the information received from sensors (temperature sensors) and determines a response, which is carried out by effectors (furnace or air conditioner).
To put this in human terms, we must understand that we are made up of chemicals in solutions. In order for the chemistry to work correctly (survival), the composition of the fluids inside cells (intracellular fluid, ICF) and outside cells (extracellular fluid, ECF) must be kept within a precisely maintained range. ECF, also called interstitial fluid, intercellular fluid, or tissue fluid, is found in two principal places in humans: the narrow spaces between the cells of tissues and in blood vessels. In the blood vessels it is termed plasma. These fluids must be kept in optimal ranges by homeostatic mechanisms. For example, you can detect and respond to external changes (e.g., drinking water when you eat salty foods), which you perceive as a response to your whole body’s environment, but these types of responses occur at a cellular level. Because of the salt you ingested, the ECF has more sodium than the ICF, which causes changes in the water content in the cells of your brain. These cells respond with signals that you perceive as thirst. Drinking water restores the balance between the ECF and the ICF.
In the above example of salty foods and thirst, the cells, organs, and organ systems in your body are interdependent on one another: you ate the salty food (digestive system) and the salt was absorbed into the blood stream (cardiovascular system). This caused a change in the extracellular fluids (changing conditions) in the cells of the brain (nervous system), which in turn acted on the musculoskeletal system and digestive system so that you could acquire the necessary water. These interactions achieved a return to normal extracellular conditions, otherwise known as a feedback loop.
Note that there are six critical elements for homeostasis to work properly: a sensor (1) to respond to a stimulus away from the normal condition, which is called a controlled condition or set point (2). This change needs to be communicated by an input signal (3) to send information to a control center (4). This control center integrates the input signals and provides a control signal (5) through nerve impulses or chemical signals to an effector (6), which is a body structure that can provide a response to the change away from the set point. This response either defends the set point by returning to it (negative feedback) or moves the controlled condition farther away from the set point (positive feedback). From the cellular to the organismal level, your body functions using these homeostatic mechanisms to maintain function.
The three basic components that make up a feedback system are shown in Figure 1.15: a sensor, an integrating center (control), and an effector.
A sensor ( also known as a receptor) is a structure in the body that responds to a physical or chemical stimulus such as heat, pH, sound, pressure, tonicity, or motion. The usual response is an electrical signal, but it can also be the release of a hormone or chemical signal. Our body has internal sensors called interoceptors that respond to our blood pH and temperature as well as proprioceptors that monitor our body position. In addition, we have numerous exteroceptors that are sensitive to changes in the external environment.
The integrating center is usually the nervous or endocrine system, which compares the input signal (afferent signal) to the normal value of the controlled condition (the set point) and determine which way to correct the change. This information is communicated to the effectors by the control signal (efferent signal). The set point is the level or value at which an internal physiological variable stabilizes and represents the optimal functional equilibrium for that variable.
An effector is an organ, usually a gland or muscle, that becomes active in response to nerve impulses. The effector response can be the result of a nerve fiber that terminates on a muscle, stimulating contraction or because of a control signal that terminates on a gland to cause secretion. Almost every organ in the body can be utilized as an effector.
What system other than the nervous system is the main regulator of homeostasis in the body?
In order to respond to changes away from a set point, the body must have a receptor to sense the change.
Homeostasis is the ability to adapt to changes in the external environment with no responses in the internal environment.
Negative Feedback: using the example of the thermostat from above, if the temperature in the room goes above the set point, the air conditioner is activated by the control center. Cool air is produced and the temperature of the room is decreased. Once the temperature reaches the set point, the control center turns off the air conditioner. The cold air counteracts the original rise in temperature, so the control system is negative or opposite the change. Conversely, if the room temperature falls, the heater is turned on and this effector will again bring the room back to the set point (see Figure 1.16).
The body uses the same principles to achieve negative feedback loops. Negative feedback occurs when a change in a variable triggers a response that adjusts in the opposite direction of the initial change.
The body is in a state of dynamic constancy, which means that fluctuations constantly occur above or below a set point and the body responds, usually with negative feedback mechanisms (see Figure 1.17). The set point is just the average value of the range of the variable. The sensitivity of the negative feedback mechanism can be observed by measuring how much deviation from the set point occurs before a compensating response is activated, which is indicated by the normal range in Figures 1.16 above and 1.17 below. Control can be further refined by the addition of antagonistic effectors that have the opposite effect on the variable. Even more efficient control utilizes two sensors and two effectors. They are usually antagonistic to each other.
Positive Feedback: in this type of feedback loop, the response of the effectors to any change in the variable causes an amplification of the changes. In other words, a change causes the effectors to respond in the same direction as the change. The control center reinforces the changes until the stimulus stops. The "text book" example of this is the positive feedback of labor contractions, illustrated by Figure 1.18. Obviously, when the baby's head no longer stretches the cervix, the stimulus no longer causes the brain to release oxytocin and uterine contractions diminish.
Dynamic constancy is the ability of the body to use antagonistic effectors to respond in positive feedback.
Click on the arrow on the left figure that represents an afferent signal from the nervous or endocrine system.
Which of the following is true of dynamic constancy?
Fluctuations occur above a set point
Fluctuations occur below a set point
Negative feedback responses
There is a range allowed in the fluctuations before a response occurs
All of the above are true of dynamic constancy
Negative feedback responses return a monitored variable to the set point.
Put the following steps of homeostasis in the correct order.
the change away from the set point is communicated by an input (afferent) signal
a sensor responds to a stimulus away from the set point
integration of information at the control center results in a control (efferent) signal
the response either defends the set point by returning to it (negative feedback) or moves the controlled condition farther away from the set point (positive feedback)
an effector provides a response to the change away from the set point
information arrives at a control center
A set point is the average value of the normal range of the variable, so the body can always change set points.
Look back up at Figures 1.4 through 1.10. If you want to describe something in them to someone who could not see them, how would you begin to speak about the structures? How would you be able to tell whether the hand in Figure 1.4 is palm up or down? If a surgeon needed to operate on the right hand but thought it was the left, they would be risking a malpractice suit. Correct diagnosis requires communication, and communication requires terminology. Because medical procedures have to be precise, the sciences of anatomy and physiology use detailed, accurate language to describe where something is located in the body.
First, no matter what position the body you are describing is in, you must have an initial point of reference to understand the terminology. Figure 1.19 shows a male and female in anatomical position, the specific position that is used to describe the relationships of the body parts. Note that the person stands with feet shoulder width apart with their arms at their sides, with palms of the hands and toes of the feet facing forward. The observer can then use anatomical terms such as lateral, medial, superior, and others to describe the patient. There are also two special terms that are used to tell whether the person is laying face up or face down: supine and prone.
Once the anatomical position is assumed, we can begin to assign directional terms to locate body structures. Table 1.3 lists these terms and their definitions. You should note that most terms come in pairs with words that have opposite meanings (anterior/posterior, superior/inferior, proximal/distal), but be aware that you use these directional terms to describe the position of one structure relative to another. For example, your knee is superior to your foot, but both are inferior to the hip and the rest of your body. It is extremely important to remember that left and right are always in relation to the subject, not to you!
Table 1.3 Directional Terms
What is the directional term you would use to tell an anatomist that your right hand is on a different side than your left foot?
Planes and Sections
When studying an organ or a body region, especially in the imaging tests shown in Figures 1.4 to 1.10, you are seeing only a section of the body or organ. How do you explain where the baby's head is in Figure 1.7 when you are only seeing a two-dimensional picture? To be able to describe the sections, additional terminology is needed. A plane of section refers to an imaginary flat surface that passes through the body parts or organ, dividing it in to sections such as those viewed in Figure 1.20. There are four planes that pass through the body: frontal, transverse, sagittal, and oblique.
Frontal plane (blue in Figure 1.20). This vertical plane is parallel to the long axis and divides the body or an organ into anterior (ventral) and posterior (dorsal) portions. In the head, this plane is called the coronal plane.
Transverse plane (green in Figure 1.20). Also called the horizontal plane or cross-sectional plane, this divides the body or organ into superior (cranial, cephalic) and inferior (caudal) portions and is perpendicular to the long axis.
Sagittal plane (red and yellow in Figure 1.20). Sagitta means arrow in Latin. The sagittal plane is vertical, parallel to the long axis, and divides the body or organ into right and left sides, but because this can be done away from the midline, we have a specific term for dividing the body or organ into equal halves: the midsagittal plane (red). Any vertical plane that divides the body or organ into unequal right and left sides is called a parasagittal plane (yellow).
Oblique plane (not shown in Figure 1.5). The imaginary line for the three previous planes are at right angles to the organ or body, but this plane passes through structures at a slant and is neither perpendicular or parallel to any of the previous sections.
Microscopic sections. Please recognize that when you look through a microscope, you may see several planes of section within the field of view: cross-sectional (transverse), longitudinal (sagittal), and oblique.
What color is the coronal plane shown in the figure?
Body Regions: Terminology of Surface Anatomy
Medical professionals and scientists use regional terms to identify specific areas on the surface of the body. Surface anatomy is, after all, how a patient presents themselves! The body is divided into five major regions: head, neck, trunk, upper limb, and lower limb. These are further subdivided into the regions in the following list and illustrated in Figure 1.21 below. It will help you a great deal with the rest of the course if you learn the terms now.
Cephalic (head): cranium (skull), facial (face), frontal (forehead), orbital (eye area), nasal (nose area), buccal (cheek area), oral (mouth), mental (chin)
Trunk: further divided into three sections: thoracic (the area between the neck and abdomen that is surrounded by the ribs, sternum, and costal cartilages; chest), abdominal (the anterior portion of the trunk just inferior to the ribs; abdomen), and pelvic (portion of the trunk inferior to the abdomen and overlying the pelvis anteriorly)
Thoracic: sternal (breastbone area), axilla/axillary (armpit), pectoral (chest), mamma (breast)
Abdominal: umbilical (navel)
Pelvic: inguinal (area where thigh and trunk join; groin), pubic (anterior pelvis; genital region)
Upper LImb: acromial (point of shoulder), deltoid (curve of the shoulder; formed by the deltoid muscle), brachial (arm), antecubital (anterior surface of the elbow), antebrachial (forearm), carpal (wrist)
Hand: manus (hand), digital (fingers), palmar/volar (palm), pollex (thumb)
Lower Limb: Coxal (hip), femoral (thigh), patellar (anterior surface of the knee), crural (leg), fibular (lateral part of leg), tarsal (ankle)
Foot: pedal (foot), digital (toes), dorsum (top of foot)
Posterior Landmarks (note many of the regions above apply here as well)
Cephalic (head): cranium (skull), occipital (base of skull)
Trunk: scapular (shoulder blade), vertebral (spinal column), lumbar (area of the back between the ribs and hips; the loin), sacral (area between the hips and the base of the spine), gluteal (buttock)
Upper Limb: olecranal or cubital (posterior surface of elbow)
Lower Limb: femoral (thigh), popliteal (posterior knee), sural (the posterior surface of the leg; calf), calcaneal (heel), plantar (sole of foot). Note the posterior figure below has the feet slightly raised in order to show the calcaneal and plantar regions.
Because of the word mental, the mens is located in the cranium
1.6 Body Cavities
The terms for the regions in Figure 1.21 deal with surface anatomy, but what about the organs and organ systems beneath the skin? There are internal body cavities in which these organs are found, called the dorsal (posterior) body cavity and the ventral (anterior) body cavity (see Figure 1.22). They are different in both embryological development and the membranes that line them, but they both protect and organize the organs within them.
The dorsal body cavity can be further divided into the Cranial cavity and the Vertebral cavity (canal). The cranial cavity contains the brain and is formed by the cranial bones. The vertebral cavity protects the spinal cord and is formed by the vertebral column, or backbone.
The ventral body cavity (also called the coelom) is much larger than the dorsal cavity and is divided into two major cavities, each of which contains smaller regions. The superior cavity is called the thoracic cavity, or chest cavity, and is separated from the rest of the ventral body cavity by the major muscle used in breathing, the diaphragm. The organs in the thoracic cavity have their own subdivisions: the right and left pleural (lung) cavities, the pericardial cavity surrounding the heart, and a central region called the mediastinum that contains the thymus, esophagus, trachea, large blood vessels, and in the lower portion the pericardial cavity.
Inferior to the diaphragm is the abdominopelvic cavity, extending to the inguinal region and protected by trunk muscles and the bones of the pelvis. As the name suggests, this cavity is also subdivided into two regions: the abdominal cavity and the pelvic cavity, though there is no actual anatomical structure to divide the space. The organs in these cavities are called the viscera. The abdominal cavity contains the stomach, spleen, liver, gallbladder, small intestine, and portions of the large intestine. The pelvic cavity contains the remaining portions of the large intestine, the urinary bladder, and the reproductive organs.
Membranes in the Ventral Body Cavity
Rub your hands together. After a few moments, notice the heat from the friction you develop and you probably know from experience that, if you keep on rubbing, your palms will begin to hurt. Now think about your heart and lungs: they constantly move against each other and the walls of the thoracic cavity as the heart beats within the pericardial cavity and you breathe. How does your body prevent this movement from causing friction and pain? The answer in the ventral body cavity is a thin, pliable membrane (called a serous membrane) that surrounds the moving organs and produces a watery fluid that allows almost frictionless movement. It covers the moving organs with the visceral layer and lines the cavities with a parietal layer. There is a potential space between them containing a serous fluid, a watery substance secreted by the cells of the visceral and parietal layers that acts as a lubricant. The serous membrane surrounding the lungs is called the pleura in the right and left pleural cavities. The single cavity surrounding the heart is called the pericardial cavity and the membrane is termed the pericardium. The peritoneum is the serous membrane of the peritoneal cavity in the abdomen. The pleural, pericardial, and peritoneal membranes all have both a parietal layer and a visceral layer.
Abdominopelvic Quadrants and Regions
The organs in the abdominopelvic cavity are located in specific areas. In order to accurately define where they can be found, the cavity is partitioned into four quadrants and nine regions. If you make an imaginary line vertically and another horizontally intersecting at the umbilicus as seen on the right side of Figure 1.23, you end up with four approximately equal divisions of the cavity called the abdominopelvic quadrants. The names of these quadrants are the right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ), and the left lower quadrant (LLQ). These quadrants are commonly used by clinicians to describe the sites of abdominal pain or other pathology. The system on the left of Figure 1.23 divides the cavity into nine abdominopelvic regions. The regions include:
Right hypochondriac: (chondro = cartilage, which refers to the cartilage of the ribs in this region), contains the liver, gallbladder, right kidney.
Epigastric: (epi = above or upon; gastric = stomach), contains the stomach, liver, and pancreas.
Left hypochondriac: contains the spleen, colon, left kidney, and pancreas.
Right lumbar: contains the right (ascending) colon, liver, and gallbladder.
Umbilical: contains the small intestine.
Left lumbar: contains the left (descending) colon, small intestine, and left kidney.
Right iliac: contains the cecum (connection between the small and large intestines) and appendix.
Hypogastric: contains the reproductive organs, sigmoid colon, and urinary bladder.
Left iliac: contains the descending and sigmoid colon.
Click on the number or letter that represents the pelvic cavity.
Click on the number or letter that indicates the mediastinum.
Appendicitis is diagnosed when a patient presents with pain in the
left lower quadrant
right lower quadrant
right inguinal region
1. Define anatomy and physiology. Which is the study of function? Which is the study of structure? How do they interact?
2. Differentiate between signs and symptoms. What are the vital signs?
3. Which of the diagnostic tests assess structure? Which assess function? If you argue that they do both, still try to organize them in your memory.
4. Know all terms in boldface type and be able to define them. Build a glossary of terms from the text. An example to help you start is in the table below:
Groups of atoms bonded in a 3-dimensional shape
Organs with similar functions
5. What are the levels of organization in the human body? What is the relationship between these levels and the function of the body?
6. What are the six life processes of the human body?
7. Build your own table summarizing the eleven organ systems using the format below:
Organ System Name
8. Define homeostasis.
9. Draw a diagram illustrating negative feedback using set point, range, sensor, integrating center, effector, input signal (afferent), and control signal (efferent). Explain the function of each component.
10. Draw a diagram illustrating positive feedback.
11. What is meant by the term dynamic constancy? Why is it important to understand in physiology?
12. Describe anatomical position. Why is it important?
13. Make a table for directional terms and planes of section. Alternatively, draw a human or body part and illustrate the directional terms and planes of section.
14. Why do we need to use sections in anatomy?
15. Explain how proximal/distal differs from superior/inferior.
16. Build your own summary table of the regional terms for the body. Alternatively, draw a human in anatomical position and label the anterior and posterior landmarks.
17. Make a table for the body cavities, identifying the major organs within them.
18. List and describe the serous membranes that line the ventral body cavities.
19. Draw the abdominopelvic quadrants. Draw the abdominopelvic regions, including the major organs found within them. Alternatively, you may make a table listing them.
Figure 1.1: Created by C.L. Chooljian in Adobe Photoshop CC.
Figure 1.3: Author's personal photograph.
Figure 1.8: Image courtesy of US National Institute on Aging, Alzheimer's Disease Education and Referral Center in the public domain via Wikimedia Commons.
Figure 1.14: Created by C.L. Chooljian in Adobe Photoshop CC.
Figure 1.16: Created by C.L. Chooljian in Adobe Photoshop CC.
Figure 1.17: Created by C.L. Chooljian in Adobe Photoshop CC.
Figure 1.19: Created by C.L. Chooljian in Adobe Photoshop CC.
Figure 1.20: Image courtesy of Richfield, David (2014). "Medical gallery of David Richfield". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.009. ISSN 2002-4436 under GNU Free Documentation License via Wikimedia Commons.
Table 1.1: Created by C.L. Chooljian in Adobe Photoshop CC.
Table 1.2: Created by C.L. Chooljian in Adobe Photoshop CC.
Table 1.3 Created by C.L. Chooljian in Adobe Photoshop CC.
Figures in Questions
Concept Review: Organ Systems: Image courtesy of Persian Poet Gal in the public domain via Wikimedia Commons.