The first three chapters provide an overview of the body and describe its main structures. Thanks again to Graeme Chambers for his patience in preparing the new and revised artwork.
The body and its constituents
Introduction to the human body
ANIMATIONS
Physiology is the study of how the body systems work and the ways in which their integrated activities maintain the life and health of the individual. Pathology is the study of abnormalities and how they affect bodily functions, often causing disease.
Levels of structural complexity
Learning outcome
Systems consist of a number of organs and tissues that together contribute to one or more survival needs of the body. For example, the stomach is one of several organs of the digestive system, which has its own specific function.
The internal environment and homeostasis
Learning outcomes
Homeostasis
The composition of the internal environment is tightly controlled and this fairly constant state is called homeostasis. When the incoming signal indicates that an adjustment is needed, the control center responds and changes the output to the effector.
Negative feedback mechanisms
When body temperature rises back into the normal range, the temperature-sensitive nerve endings are no longer stimulated and their signals to the hypothalamus stop. Most homeostatic controls in the body use negative feedback mechanisms to prevent sudden and severe changes in the internal environment.
Positive feedback mechanisms
Homeostatic imbalance
Many such situations, including the effects of variable factor anomalies in Box 1.1, are explained in later chapters.
Survival needs of the body
Communication
Transport systems
The heart is a muscular bag that pumps blood throughout the body and maintains blood pressure. The lymphatic system (Fig. 1.8) consists of a series of lymph vessels, which begin as blind end tubes in the spaces between the blood capillaries and tissue cells.
Internal communication
Sensory nerves send signals from the body to the appropriate areas of the brain, where the incoming information is analyzed and collected. The endocrine system consists of a number of separate glands located in different parts of the body.
Communication with the external environment
Speech produces recognizable sounds by coordinated contraction of the muscles of the throat and cheeks and movements of the tongue and lower jaw. The skeleton forms the bony framework of the body (chapter 16), and movement takes place at joints between bones.
Intake of raw materials and elimination of waste
Although these senses are usually considered separate and distinct from each other, one sense is rarely used alone (Fig. 1.10). Sound is a means of communication produced in the larynx as a result of blowing air through the space between the vocal cords (see Fig. 10.8) during expiration.
Intake of oxygen
The upper respiratory system carries air between the nose and the lungs during breathing (Ch. 10). Air passes through a system of passages consisting of the pharynx (also part of the digestive tract), the larynx (voice box), the trachea, two bronchi (one bronchi to each lung) and a large number of bronchial passages (Fig .1.11) ).
Ingestion of nutrients (eating)
The nitrogen needed by the body is obtained by eating foods containing protein, mainly meat and fish. Most of these glands synthesize digestive enzymes that are involved in the chemical breakdown of food.
Elimination of wastes
Protection and survival
Protection against the external environment
The epidermis lies superficially and consists of several layers of cells that grow towards the surface from its deepest layer. The dermis contains tiny sweat glands that have small ducts or ducts that lead to the surface.
Protection against infection
The surface layer consists of dead cells that are constantly rubbed off and replaced from below. The epidermis represents a barrier between the moist internal environment and the dry atmosphere of the external environment.
Movement
Under the control of the volitional nervous system, skeletal muscles (Figure 1.16) maintain posture and balance and move the skeleton. A brief description of the skeleton is given in Chapter 3, and a more detailed description of the bones, muscles and joints is presented in Chapter 16.
Survival of the species
They then swim up through the uterus and fertilize the egg in the fallopian tube. Men do not have this cycle, but hormones similar to those in women are involved in sperm production and maturation.
Introduction to the study of illness
Aetiology
Pathogenesis
Introduction to the chemistry of life
Atoms, molecules and compounds
The atomic weight of an element is the sum of the protons and neutrons in the atomic nucleus. This leaves the sodium atom of the compound with eight electrons in its outer (second) shell, and therefore stable.
Acids, alkalis and pH
The low pH of the stomach fluids destroys microbes and toxins that can be ingested in food or drink. Normal metabolic activity of body cells produces certain acids and bases, which could alter the pH of the tissue fluid and blood.
Important biological molecules
Carbohydrates
Amino acids and proteins
Of the amino acids used in human protein synthesis, there is a basic common structure, including an amino group (NH2), a carboxyl group (COOH), and a hydrogen atom. Proteins are made of amino acids linked together and are the main family of molecules that make up the human body.
Lipids
In human biochemistry, 20 amino acids are used as the main building blocks of protein, although there are others; for example, there are some amino acids that are only used in certain proteins, and some are only seen in microbial products. As in the formation of glycosidic bonds, when two amino acids join together, the reaction displaces a molecule of water and the resulting bond is called a peptide bond.
Nucleotides
When fat is broken down under optimal conditions, more energy is released than when glucose is completely broken down. Fats are classified as saturated or unsaturated, depending on the chemical nature of the fatty acids present.
Enzymes
Movement of substances within body fluids
However, blood cells and large protein molecules in the plasma are too large to cross and therefore remain in the blood. Conversely, if the plasma water concentration decreases, so that the plasma becomes more concentrated than the intracellular fluid in the red blood cells (the plasma becomes hypertonic), the water moves passively by osmosis from the blood cells into the plasma, and the blood cells shrink (Fig. 2.13).
Body fluids
The composition of intracellular fluid (ICF) is largely controlled by the cell itself, because there are selective uptake and discharge mechanisms in the cell membrane. This concentration difference occurs because, although sodium diffuses down its concentration gradient into the cell, there is a pump in the membrane that selectively pumps it back out.
The cells, tissues and organisation of the body
Organs are grouped together to form systems, each of which performs a specific function that maintains homeostasis and contributes to the health of the individual (see Fig. 1.2, p. 5). The terminology used to describe the anatomical relationships of body parts, the skeleton and the cavities within the body is described next.
The cell: structure and functions
Plasma membrane
They participate in aerobic respiration, the processes by which chemical energy is available in the cell. Ribosomes are also found on the outer surface of the nuclear envelope and rough endoplasmic reticulum (see Figure 3.3 and below), where they produce proteins for export from the cell.
The cell cycle
The centrioles migrate, one to each end of the cell, and the nuclear envelope disappears. The organelles of the daughter cells are incomplete at the end of cell division, but they develop during interphase.
Transport of substances across cell membranes
Each of the original 46 chromosomes (called a chromatid at this stage) is paired with its copy in a double chromosome unit. The centromeres separate and one of each pair of sister chromatids (now called chromosomes again) migrates to each end of the spindle as the microtubules that form the mitotic spindle contract.
Passive transport
Then the carrier changes its shape and deposits the substance on the other side of the membrane (Fig. 3.10). This active transport mechanism maintains unequal concentrations of sodium (Na+) and potassium (K+) ions on either side of the plasma membrane.
Tissues
Epithelial tissue (Fig. 3.12)
Simple epithelium
Stratified epithelia
This forms a tough, relatively waterproof protective layer that prevents the living cells underneath from drying out. This protects wet surfaces subject to wear and prevents them from drying out, e.g.
Connective tissue
The collagen fibers formed during healing shrink as they age, sometimes interfering with the function of the affected organ and neighboring structures. They are an important part of the body's defense mechanisms, as they actively phagocytose, capture and digest cellular debris, bacteria and other foreign substances.
Loose (areolar) connective tissue (Fig. 3.16)
Adipose tissue (Fig. 3.17)
The amount of adipose tissue in an individual is determined by the balance between energy intake and expenditure. When brown tissue is metabolized, it produces less energy and significantly more heat than other fat, helping to maintain body temperature.
Lymphoid tissue (Fig. 3.18)
It is found in the support of the kidneys and eyes, between muscle fibers and under the skin, where it acts as a heat insulator and energy store.
Dense connective tissue
There are few cells and the matrix consists mainly of masses of elastic fibers secreted by fibroblasts.
Blood
Cartilage
It consists of dense masses of white collagen fibers in a matrix similar to that of hyaline cartilage with the cells widely dispersed.
Bone
Muscle tissue
Bundles of fibers form muscle layers, such as those found in the walls of the above structures. The ends of the cells and their branches are in very close contact with the ends and branches of adjacent cells.
Nervous tissue
The heart has an intrinsic pacing system, which means that it beats in a coordinated manner without external nerve stimulation, although the rate at which it beats is influenced by autonomic nerve impulses, certain hormones, local metabolites and other substances (see Chap. 5). .
Tissue regeneration
Membranes
Epithelial membranes
The parietal layer surrounds the cavity, and the visceral layer surrounds the organs (inside) within the cavity. For example, the heart changes its shape and size during each beat, and frictional damage prevents the distribution of the pericardium and its serous fluid.
Glands
They consist of a double layer of loose areolar connective tissue lined with simple squamous epithelium. The serous fluid between the visceral and parietal layers allows an organ to slide freely within the cavity without being damaged by friction between it and adjacent organs.
Organisation of the body
Anatomical terms
The skeleton
Axial skeleton
Skull
The coccyx consists of four end vertebrae fused into a small triangular bone that articulates with the sacrum above. In the thoracic region, the ribs articulate with vertebrae forming joints allowing the ribcage to move during breathing.
Thoracic cage
Appendicular skeleton
Cavities of the body
Cranial cavity
Thoracic cavity
Posteriorly – the lumbar vertebrae and muscles that form the posterior abdominal wall Laterally – the lower ribs and parts of the muscles of the abdominal wall. Most of the abdominal cavity is occupied by the organs and glands of the digestive system (Figs. 3.33 and 3.34).
Pelvic cavity
Disorders of cells and tissues
Neoplasms or tumours
Causes of neoplasms
Carcinogens
Exposure to ionizing radiation, including X-rays, radioactive isotopes, environmental radiation, and ultraviolet rays from the sun, can cause malignant changes in some cells and kill others. Examples include hepatitis B virus, which can cause liver cancer (p. 326) and human papillomavirus, which is associated with cervical cancer (p. 453).
Host factors
Some viruses are known to cause malignant changes in animals and there are indications of similar involvement in humans. Viruses enter cells and insert their DNA or RNA into the host cell's genetic material, causing mutation.
Growth of tumours
Cell differentiation
Cells are affected during mitosis, so those that normally undergo continuous controlled division are most susceptible.
Encapsulation and spread of tumours
Groups of tumor cells break off and are carried to lymph nodes, where they settle and can grow into secondary tumors. Phagocytosis of tumor cells in the emboli is unlikely because these are protected by the clot.
Effects of tumours
For example, if a malignant tumor in an abdominal organ invades the visceral peritoneum, tumor cells can metastasize to the folds of the peritoneum or an abdominal or pelvic organ. The locations of blood-borne metastases depend on the location of the original tumor and the anatomy of the circulatory system in the area.
Causes of death in malignant disease
It is the severe weight loss accompanied by progressive weakness, loss of appetite, wasting and anemia that is usually associated with advanced metastatic cancer.
The blood
A blood clot in serum
Blood in the blood vessels is always in motion due to the pumping action of the heart. The first part of the chapter describes normal blood physiology, and the later sections deal with some disorders of the blood.
Plasma
In red blood cells, in combination with hemoglobin, oxygen and carbon dioxide are also transported (p. 58). Red blood cells are biconcave discs; they do not have a nucleus, and their diameter is about 7 micrometers (Figure 4.3).
Life span and function of erythrocytes
Iron is transported in the bloodstream bound to its transport protein, transferrin, and stored in the liver. When the erythropoietin level is low, the formation of red blood cells does not occur even in the presence of hypoxia, and anemia develops (the inability of the blood to carry enough oxygen for the body's needs).
Granulocytes (polymorphonuclear leukocytes)
Eosinophils, although capable of phagocytosis, are less active in this than neutrophils; their specialized role appears to be in eliminating parasites, such as worms, that are too large to be phagocytosed. A type of cell very similar to basophils, except found in tissue, not in the circulation, is the mast cell.
Agranulocytes
For example, in the lungs, resistant bacteria such as tuberculosis bacilli and inhaled inorganic dust can be trapped in such capsules. They circulate in the blood and are present in large numbers in lymphatic tissue such as lymph nodes and the spleen.
Haemostasis
Clot shrinkage pulls the edges of the damaged vessel together, reducing blood loss and sealing the hole in the vessel wall. An inactive substance called plasminogen is present in the clot and is converted to the enzyme plasmin by activators released from the damaged endothelial cells.
Erythrocyte disorders
Anaemias
Iron deficiency anaemia
Because of the relative inefficiency of iron absorption, deficiency often occurs, even in individuals whose requirements are normal. Iron absorption is usually increased after bleeding, but may be decreased with abnormalities in the stomach, duodenum or jejunum.
Megaloblastic anaemias
Iron requirements also increase with chronic blood loss, the causes of which include stomach ulcers (p. 315), heavy menstrual bleeding (menorrhagia), hemorrhoids or carcinoma of the gastrointestinal tract (p. 316, 320). Since iron absorption is dependent on an acidic environment in the stomach, an increase in gastric pH can lower it; this may result from part of the stomach being removed, or in pernicious anemia (see below), where the acid-releasing (parietal) cells of the stomach are destroyed.
Vitamin B 12 deficiency anaemia
Folic acid deficiency anaemia
Aplastic anaemia
Haemolytic anaemias
Congenital haemolytic anaemias
In this disorder, the mother's immune system produces antibodies against the baby's red blood cells, causing the fetus's erythrocytes to be destroyed. During pregnancy, the placenta protects the baby from the mother's immune system, but during labor some fetal red blood cells may enter the mother's circulation.
Acquired haemolytic anaemias
Individuals do not normally produce antibodies against their own red blood cell antigens; if they did, the antigens and antibodies would react, resulting in clumping and lysis of RBCs (see Figure 4.7). However, if individuals receive a blood transfusion that carries antigens different from their own, their immune system will recognize them as foreign, create antibodies against them, and destroy them (transfusion reaction).
Normocytic normochromic anaemia
The breakdown products of hemolysis deposit and block the filtration mechanism of the nephron, impairing kidney function.
Polycythaemia
Leukocyte disorders
Leukopenia
Granulocytopenia (neutropenia)
Leukocytosis
Leukaemia
Types of leukaemia
Leukocytosis is a feature of chronic leukemia in which the bone marrow is filled with immature and abnormal leukocytes, although this varies depending on the form of the disease. It is most often seen in the elderly; disease progression is usually slow and survival time can be as long as 25 years.
Haemorrhagic diseases
Thrombocytopenia
Vitamin K deficiency
Disseminated intravascular coagulation (DIC)
Congenital disorders
Recurrent bleeding into the joint is common, causing severe pain and, in the long term, cartilage damage. In this disease, a deficiency in von Willebrand factor causes low levels of factor VIII.
The cardiovascular system
Position 78
The right side of the heart pumps blood to the lungs (pulmonary circulation), where gas exchange takes place, i.e. The left side of the heart pumps blood into the systemic circulation, which supplies the rest of the body.
Blood vessels
Arteries and arterioles
The amount of muscular and elastic tissue varies in the arteries depending on their size and function. In the large arteries, sometimes called elastic arteries, the tunica media consists of more elastic tissue and less smooth muscle.
Capillaries and sinusoids
These proportions gradually change as the arteries branch many times and become smaller, until in the arterioles (the smallest arteries) the tunica media consists almost entirely of smooth muscle. This allows a much faster exchange of substances between the blood and the tissues, useful for example in the liver, which regulates the composition of blood coming from the gastrointestinal tract.
Veins and venules
Blood supply
Control of blood vessel diameter
An organ's ability to control its own blood flow as needed is called autoregulation. Blood flow is increased through individual organs by vasodilation of the vessels that supply it, and decreased through vasoconstriction.
Capillary exchange
An important vasodilator is nitric oxide, which is very short-lived but important in opening the larger arteries that supply an organ.
Exchange of gases
Exchange of other substances
The total force at the arterial end of the capillary therefore drives fluid out of the capillary and into the tissue. Of the approximately 24 liters of fluid that drains from the blood through the capillary walls each day, only about 21 liters return to the bloodstream at the venous end of the capillary bed.
Heart
Posteriorly – esophagus, trachea, left and right bronchus, descending aorta, inferior vena cava and thoracic vertebrae. Lateral – the lungs – the left lung overlaps the left side of the heart Anteriorly – the sternum, ribs and intercostal muscles.
Structure
The heart wall
The pulmonary trunk leaves the heart from the upper part of the right ventricle, and the aorta leaves the upper part of the left ventricle. This large blood supply, especially to the left ventricle, emphasizes the importance of the heart to body function.
Sinoatrial node (SA node)
Atrioventricular node (AV node)
Nerve supply to the heart
Factors affecting heart rate
The most important ones are summarized in Box 5.1 and explained in more detail on page 86.
The cardiac cycle
Stages of the cardiac cycle
The first sound, 'lub', is quite loud and is due to the closure of the atrioventricular valves. Note the delay between the end of the P wave and the start of the QRS complex.
Myocardial energy sources
By examining the wave pattern and the time interval between cycles and parts of cycles, we obtain data on the condition of the myocardium and the cardiac conduction system.
Cardiac output
Stroke volume
Venous return
During inspiration, the expansion of the chest creates a negative pressure inside the chest, helping blood flow to the heart. In addition, when the diaphragm descends during inspiration, increased intra-abdominal pressure pushes blood toward the heart.
Heart rate
When the person is upright, the heart rate is usually faster than when lying down. In babies and small children, the heart rate is faster than in older children and adults.
Blood pressure
Factors determining blood pressure
Control of blood pressure (BP)
Short-term blood pressure regulation
An increase in blood pressure in these arteries stimulates the baroreceptors, increasing their input into the CVC. The CVC responds by increasing parasympathetic nerve activity to the heart; this slows down the heart.
Long-term blood pressure regulation
Pressure in the pulmonary circulation
Pulse
Provided sufficient blood reaches an extremity to nourish it, it will remain pink and warm, even if a pulse cannot be felt.
Circulation of the blood
The right pulmonary artery goes to the root of the right lung and divides into two branches. Two pulmonary veins leave each lung, returning oxygen-rich blood to the left atrium of the heart.
Systemic or general circulation
Aorta
Thoracic aorta
At the level of the sternoclavicular joint, it divides into the right common carotid artery and the right subclavian artery.
Circulation of blood to the head and neck
The external jugular vein begins in the neck at the level of the angle of the jaw. The superior sagittal sinus carries the venous blood from the superior part of the brain.
Circulation of blood to the upper limb
