On completion of this chapter, you should be able to:
Define and use terms for anatomic directions
Discuss the body systems and their functions
Know the terms for the body planes
Describe and locate the abdominal quadrants and regions
List the organs located in each major body cavity
Identify and locate the abdominal viscera and other abdominal structures and spaces
To understand the complexity of the human body and how the parts work together to function as a whole truly is to gain an appreciation of anatomy and physiology. The science of body structure (anatomy) and the study of body function (physiology) are intricately related, for each structure of the human body system carries out a specific function. Anatomy and physiology can take many forms: Gross anatomy studies the body by dissection of tissues; histology studies parts of body tissues under the microscope; embryology studies development before birth; and pathology is the study of disease processes.
From atom to organism
A review of the composition of the human body begins with an understanding that all materials consist of chemicals. The basic units of all matter are tiny invisible particles called atoms. An atom is the smallest component of a chemical element that retains the characteristic properties of that element. Atoms can combine chemically to form larger particles called molecules. For example, two atoms of hydrogen combine with one atom of oxygen to produce a molecule of water.
The next level of complexity in the human body is a microscopic unit called a cell. Although they share common traits, cells can vary in size, shape, and specialized function. In the human body, atoms and molecules associate in specific ways to form cells, and trillions of different types of cells are found within the body. All cells have specialized tiny parts called organelles, which carry on specific activities. These organelles consist of aggregates of large molecules, including those of such substances as proteins, carbohydrates, lipids, and nucleic acids. One organelle, the nucleus, serves as the information and control center of the cell.
Cells that are organized into layers or masses that have common functions are known as tissue. The four primary types of tissue in the body are muscle, nervous, connective, and epithelial tissues. Groups of different tissues combine to form organs —complex structures with specialized functions, such as the liver, pancreas, or kidneys. One organ may have more than one type of tissue (e.g., the heart mainly consists of muscle tissue, but it is also covered by epithelial tissue and contains connective and nervous tissue).
A coordinated group of organs are arranged into organ or body systems. For example, the digestive system consists of the mouth, esophagus, stomach, intestines, liver, gallbladder, and pancreas. Body systems make up the total part or organism that is the human body.
All physical and chemical changes that occur within the body are referred to as metabolism. The metabolic process is essential to digestion, growth and repair of the body, and conversion of food energy into forms useful to the body. Other metabolic processes maintain the routine operations of the nerves, muscles, and other body parts.
The anatomic structures and functions of all body parts are directed toward maintaining the life of the organism. To sustain life, an organism must have the proper quantity and quality of water, food, oxygen, heat, and pressure. Maintenance of life depends on the stability of these factors. Homeostasis is the ability to maintain a steady and stable internal environment. Stressful stimuli, or stressors, disrupt homeostasis.
Vital signs are medical measurements used to ascertain how the body is functioning. These measurements include body temperature and blood pressure and rates and types of pulse and breathing movements. A close relationship has been noted between these signs and the homeostasis of the body, as vital signs are the result of metabolic activities.
A body system consists of a group of tissues and organs that work together to perform specific functions. Each system contributes to the dynamic, organized, and carefully balanced state of the body. The sonographer should be familiar with at least the integumentary, lymphatic, skeletal, endocrine, muscular, respiratory, and nervous systems of the body. The remaining systems—circulatory, digestive, urinary, and reproductive—should be thoroughly understood by the sonographer. Table 4-1 lists the components and functions of human body systems.
|Integumentary||Skin, hair, nails, sweat glands||Covers and protects tissues, regulates body temperature, supports sensory receptors|
|Skeletal||Bones, cartilage, joints, ligaments||Supports the body, provides framework, protects soft tissues, provides attachments for muscles, produces blood cells, stores inorganic salts, provides calcium storage|
|Muscular||Skeletal, cardiac, smooth muscle||Moves parts of skeleton, provides locomotion, pumps blood, aids movement of internal materials, produces body heat|
|Nervous||Nerves and sense organs, brain, and spinal cord||Receives stimuli from external and internal environment, conducts impulses, integrates activities of other systems|
|Endocrine||Pituitary, adrenal, thyroid, pancreas, parathyroid, ovaries, testes, pineal, and thymus gland||Regulates body chemistry and many body functions|
|Lymphatic||Lymph nodes||Returns tissue fluid to the blood, carries specific absorbed food molecules, defends the body against infection|
|Circulatory||Heart, blood vessels, blood, lymph and lymph structures||Moves the blood through the vessels and transports substances throughout the body|
|Respiratory||Lungs, bronchi, and air passageways||Exchanges gases between blood and external environment|
|Digestive||Mouth, tongue, teeth, salivary glands, pharynx, esophagus, stomach, liver, gallbladder, pancreas, small and large intestines||Receives, breaks down, and absorbs food and eliminates unabsorbed material from the body|
|Urinary||Kidney, bladder, ureters||Excretes waste from the blood, maintains water and electrolyte balance, and stores and transports urine|
|Reproductive||Testes, scrotum, spermatic cord, vas deferens, ejaculatory duct, penis, epididymis, prostate, uterus, ovaries, fallopian tubes, vagina, breast||Reproduction; provides for continuation of the species|
The circulatory system: Blood composition and function
Knowledge of the circulatory system is fundamental to understanding human physiology. The circulation of blood throughout the body serves as a vital connection to the cells, tissues, and organs to maintain a relatively constant environment for cell activity. Blood is composed of plasma and “formed elements.” The plasma is broken down into 7% proteins (albumins, globulins, and fibrinogen), 91% water, and 2% other solutes (ions, nutrients, waste products, gases, regulatory substances) ( Figure 4-1 ). The “formed elements” are comprised of platelets, leukocytes (neutrophils, lymphocytes, monocytes, eosinophils, and basophils), and erythrocytes.
Plasma makes up 55% of the total blood volume and consists of about 92% water. The remaining 8% comprises numerous substances suspended or dissolved in this water. Hemoglobin of the red cells accounts for two thirds of the blood proteins, with the remaining consisting of plasma proteins. These include serum albumin, globulin, fibrinogen, and prothrombin.
Serum album constitutes 53% of the total plasma proteins. It is produced in the liver and serves to regulate blood volume. Globulin can be separated into alpha, beta, and gamma globulin. The latter is involved in immune reactions in the body’s defense against infection. Fibrinogen is concerned with coagulation of blood. Prothrombin is produced in the liver and participates in blood coagulation. Vitamin K is essential for prothrombin production.
Functions of the blood.
The blood is responsible for a variety of functions, including transportation of oxygen and nutrients, defense against infection, and maintenance of pH. The red blood cells, white blood cells, and platelets are continually being destroyed so the body must make new ones to replace the destroyed cells every second. Two kinds of connective tissue make blood cells for the body: myeloid tissue (red bone marrow) and lymphatic tissue (lymph nodes, thymus, spleen). The formation of new blood cells is called hemopoiesis. As the blood cells mature, they move into the circulatory vessels.
Acidic versus alkaline.
Blood is thicker than water and therefore flows more slowly than water. The specific gravity of blood may be calculated by comparing the weight of blood versus water; with water being 1.00, blood is in the range of 1.045 to 1.065. The hydrogen ion and the hydroxyl ion are found within water. When a solution contains more hydrogen than hydroxyl ions, it is called an acidic solution. Likewise, when it contains more hydroxyl ions than hydrogen ions, it is referred to as an alkaline solution. This concentration of hydrogen ions in a solution is called the pH, with the scale ranging up to 14.0.
In water, an equal concentration of both ions exists; water is thus a neutral solution, or 7.0 on the pH scale. Human blood has a pH of 7.34 to 7.44, being slightly alkaline. A blood pH below 6.8 is a condition called acidosis; blood pH above 7.8 is known as alkalosis. Both conditions can lead to serious illness and eventual death unless proper balance is restored. To help in this process, blood plasma is supplied with chemical compounds called buffers. These buffers can act as weak acids or bases to combine with excess hydrogen or hydroxyl ions to neutralize the pH. Plasma is the basic supporting fluid and transporting vehicle of the blood. It constitutes 55% of the total blood volume.
The volume of blood in the body depends on the body surface area; however, the total volume may be estimated as approximately 9% of total body weight. Therefore blood volume is approximately 5 quarts in a normal-sized man.
The red blood cells ( erythrocytes ), white blood cells ( leukocytes ), and platelets ( thrombocytes ) make up the remainder of the blood. The percent of the total blood volume containing these three elements is called the hematocrit. Normally, the hematocrit is 45% of the total blood volume with plasma accounting for the remaining 55%.
Complete blood count.
The differential complete blood count (CBC) is a laboratory blood test that evaluates and states specific values for all these subgroups of white blood cells.
Red blood cells.
Red blood cells (RBCs) are disc-shaped, biconcave cells without a nucleus. They are formed in the bone marrow and are the most prevalent of the formed elements in the blood. Their primary role is to carry oxygen to the cells and tissues of the body. Oxygen is picked up by a protein in the red cell called hemoglobin. Hemoglobin releases oxygen in the capillaries of the tissues. The function of erythrocyte is to provide oxygen and carbon dioxide transport.
The production of RBCs is called erythropoiesis. Their life span is approximately 120 days. Vitamin B 12 is necessary for complete maturity of the RBCs. The inner mucosal lining of the stomach secretes a substance called the intrinsic factor, which promotes absorption of vitamin B 12 from ingested food. Anemia is an abnormal condition where the blood lacks either a normal number of red blood cells or normal concentration of hemoglobin. If too many RBCs are produced, polycythemia results.
As old RBCs are destroyed in the liver, part of the hemoglobin is converted to bilirubin, which is excreted by the liver in the form of bile. When excessive amounts of hemoglobin are broken down, or when biliary excretion is decreased by liver disease or biliary obstruction, the plasma bilirubin level rises. This rise in plasma bilirubin results in a yellow-skin condition termed jaundice.
White blood cells.
White blood cells (WBCs) are the body’s primary defense against infection. WBCs lack hemoglobin, are colorless, contain a nucleus, and are larger than RBCs. White cells are extremely active and move with an ameboid motion, often against the flow of blood. They can pass from the bloodstream into intracellular spaces to phagocytize foreign matter found between the cells. A condition called leukopoiesis is WBC formation stimulated by the presence of bacteria.
Neutrophils, lymphocytes, monocytes, eosinophils, and basophils are in the group of leukocytes. Their function is to ingest and destroy bacteria with the formation of pus. The functions of the leukocytes are as follows:
Neutrophil and monocyte: immune defense—phagocytosis
Lymphocyte: antibody production and cellular immune response
Eosinophil: defense against irritants that cause allergies; phagocytosis
Basophil: inflammatory response; contain heparin and control clotting
Lymphocytes and monocytes.
The lymphocytes are WBCs formed in lymphatic tissue. They enter the blood by way of the lymphatic system and contain antibodies responsible for delayed hypersensitivity reactions. Monocytes are large white cells capable of phagocytosis and are quite mobile. Their numbers are few, and they are produced in the bone marrow.
White blood cells.
White cells have two main sources: (1) red bone marrow (granulocytes) and (2) lymphatic tissue (lymphocytes). When an increase in the white cells arises from a tumor of the bone marrow, it is called myelogenous leukemia and is noted as an increase in granulocytes. On the other hand, an increase in WBCs caused by overactive lymphoid tissue is called lymphatic leukemia, with an increase in lymphocytes. In bacterial infections, the white cells increase in number (leukocytosis), with most of the increase noted in the neutrophils. A decrease in the total white cell count (leukopenia) is a result of a viral infection.
Thrombocytes, or blood platelets, are formed from giant cells in the bone marrow. They initiate a chain of events involved in blood clotting together with a plasma protein called fibrinogen. Thrombocytes are destroyed by the liver and have a life span of 8 days.
The gastrointestinal system
The gastrointestinal (GI) system consists of two major divisions: the GI tract and the accessory organs. The GI tract is a hollow tube that begins at the mouth and ends at the anus. About 25 feet long, the GI tract includes the pharynx, esophagus, stomach, small intestine, and large intestine ( Figure 4-2 ). Accessory GI organs include the liver, pancreas, gallbladder, and bile ducts and will be discussed in detail in their respective chapters. The abdominal aorta and the gastric and splenic veins also aid the GI system.
Major functions of the GI system include ingestion and digestion of food and elimination of waste products. GI complaints can be especially difficult to assess and evaluate because the abdomen has so many organs and structures that may influence pain and tenderness.
Normal findings for the GI system
Skin is free from vascular lesions, jaundice, surgical scars, and rashes.
Faint venous patterns (except in thin patients) are apparent.
Abdomen is symmetric, with a flat, round, or scaphoid contour.
Umbilicus is positioned midway between the xiphoid process and the symphysis pubis, with a flat or concave hemisphere.
No variations in the color of the patient’s skin are detectable.
No bulges are apparent.
The abdomen moves with respiration.
Guidelines for GI assessment
Fever may be a sign of infection or inflammation.
Tachycardia may occur with shock, pain, fever, sepsis, fluid overload, or anxiety. A weak, rapid, and irregular pulse may point to hemodynamic instability, such as that caused by excessive blood loss. Diminished or absent distal pulses may signal vessel occlusion from embolization associated with prolonged bleeding.
Altered respiratory rate and depth can result from hypoxia, pain, electrolyte imbalance, or anxiety. Respiratory rate also increases with shock. Increased respiratory rate with shallow respirations may signal fever and sepsis. Absent or shallow abdominal movement on respiration may point to peritoneal irritation.
Decreased blood pressure may signal compromised hemodynamic status, perhaps from shock caused by GI bleed. Sustained severe hypotension results in diminished renal blood flow, which may lead to acute renal failure. Moderately increased systolic or diastolic pressure may occur with anxiety or abdominal pain. Hypertension can result from vascular damage caused by renal disease or renal artery stenosis. A blood pressure drop of greater than 30 mm Hg when the patient sits up may indicate fluid volume depletion.
Common signs and symptoms of GI diseases and disorders.
The most significant signs and symptoms related to gastrointestinal diseases and disorders are abdominal pain, diarrhea, bloody stools, nausea, and vomiting ( Table 4-2 ).
|Signs or Symptoms||Probable Indication|
|Localized abdominal pain, described as steady, gnawing, burning, aching, or hunger-like, high in the midepigastrium slightly off center, usually on the right |
Pain begins 2–4 hours after a meal
Ingestion of food or antacids brings relief
Changes in bowel habits
Heartburn or retrosternal burning
|Pain and tenderness in the right or left lower quadrant, may be sharp and severe on standing or stooping |
Mild nausea and vomiting
Occasional menstrual irregularities
|Referred, severe upper abdominal pain, tenderness, and rigidity that diminish with inspiration |
Fever, shaking, chills, aches, and pains
Blood-tinged or rusty sputum
Dry, hacking cough
|Diarrhea occurs within several hours of ingesting milk or milk products |
Abdominal pain, cramping, and bloating
|Recurrent bloody diarrhea with pus or mucus |
Hyperactive bowel sounds
Cramping lower abdominal pain
Occasional nausea and vomiting
|Moderate to severe rectal bleeding |
Purpura (skin rash resulting from bleeding into the skin from small blood vessels)
|Bright-red rectal bleeding with or without pain |
Diarrhea or ribbon-shaped stools
Stools may be grossly bloody
Weakness and fatigue
Abdominal aching and dull cramps
|Chronic bleeding with defecation |
|Nausea and Vomiting|
|May follow or accompany abdominal pain |
Pain progresses rapidly to severe, stabbing pain in the right lower quadrant (McBurney sign)
Abdominal rigidity and tenderness
Constipation or diarrhea
|Nausea and vomiting of undigested food |
Hyperactive bowel sounds
|Headache with severe, constant, throbbing pain |
Increased noise sensitivity
Abdominal pain usually results from a GI disorder, but it can be caused by a reproductive, genitourinary, musculoskeletal, or vascular disorder; use of certain drugs; or exposure to toxins.
Constant, steady abdominal pain suggests organ perforation, ischemia, inflammation, or blood in the peritoneal cavity.
Intermittent and cramping abdominal pain suggests the patient may have an obstruction.
Ask if the pain radiates to other areas or if eating relieves the pain.
Abdominal pain may arise from the abdominopelvic viscera, the parietal peritoneum, or the capsule of the liver, kidney, or spleen, and may be acute or chronic, diffuse or localized.
Visceral pain develops slowly into a deep, dull, aching pain that is poorly localized in the epigastric, periumbilical, or hypogastric region.
Mechanisms that produce abdominal pain, including stretching or tension of the gut wall, traction on the peritoneum or mesentery, vigorous intestinal contraction, inflammation, or ischemia, may cause sensory nerve irritation.
Diarrhea is usually a primary sign of intestinal disorder. Diarrhea is an increase in the volume, frequency, and liquidity of stools compared with the patient’s normal bowel habits. It varies in severity and may be acute or chronic.
Acute diarrhea may result from acute infection, stress, fecal impaction, or use of certain drugs.
Chronic diarrhea may result from chronic infection, obstructive and inflammatory bowel disease, malabsorption syndrome, an endocrine disorder, or GI surgery.
The fluid and electrolyte imbalance may precipitate life-threatening arrhythmias or hypovolemic shock.
Hematochezia is the passage of bloody stools and may be a sign of GI bleeding below the ligament of Treitz. It may also result from a coagulation disorder, exposure to toxins, or a diagnostic test. It may lead to hypovolemia.
Nausea and vomiting.
Nausea is a sensation of profound revulsion to food or of impending vomiting. Vomiting is the forceful expulsion of gastric contents through the mouth that is often preceded by nausea.
Nausea and vomiting may occur with fluid and electrolyte imbalance; infection; metabolic, endocrine, labyrinthine, and cardiac disorders; use of certain drugs; surgery; and radiation.
Nausea and vomiting may also arise from severe pain, anxiety, alcohol intoxication, overeating, or ingestion of distasteful food or liquids.
The genitourinary system
It is important to recognize that a disorder of the genitourinary system can affect other body systems. For example, ovarian dysfunction can alter endocrine balance, or kidney dysfunction can affect the production of certain hormones that regulate RBC production.
The urinary system consists of the kidneys, ureters, bladder, and urethra ( Figure 4-3 ). The primary functions of the urinary system are the formation of urine and the maintenance of homeostasis. These functions are performed by the kidneys. Kidney dysfunction can cause trouble with concentration, memory loss, or disorientation. Progressive chronic kidney failure can also cause lethargy, confusion, disorientation, stupor, convulsions, and coma. Observation of the patient’s vital signs may give indication of hypertension, which may be related to renal dysfunction if the hypertension is uncontrolled.