Anatomy And Physiology Lecture Notes

1 BIO 110 Anatomy and Physiology I Lecture Notes Dr. Patrick Slavin I. Organization of the Body Anatomy (the study of body structure) and physiology (the study of body function) are, for convenience, organized into eleven interrelated organ systems which will be explained over the next two semesters. These eleven organ systems are as follows: (pp 6 – 7)1 - Integumentary System - skin and associated structures - Skeletal system - supporting and protecting bones and cartilages - Muscular System - muscles and movement - Lymphatic/Immune System - lymph vessels and organs, the immune response - Respiratory - oxygen supply and carbon dioxide removal - Digestive System - breakdown and absorption of food - Nervous System - response of internal and external stimuli by electrical impulses - Endocrine System - internal control by chemical hormones - Cardiovascular System - blood, blood vessels and heart - Urinary System - elimination of nitrogenous waste, water balance - Reproductive System - production of offspring We will also approach the study of the body by looking at the gradient of complexity of biology: Atoms → Compounds → Cells → Tissues → Organs → Organ Systems Anatomical Position (pp 14 – 15 allows us to consistently discuss the orientation of the body in space. A number of pairs of terms help us to describe this orientation. (p 13) - Superior – Inferior. Superior refers to structures above or toward the head, Inferior below or toward the foot. Example: the nose is superior to the mouth, the mouth is inferior to the nose. - Anterior (also called Ventral) – Posterior (also called Dorsal). Anterior refers to the front, Posterior to the back. Example: the stomach is anterior to the spine, the spine is posterior to the stomach. - Medial – Lateral. Medial means toward the midline of the body, Lateral towards the sides or away from the midline. Example: the ears are lateral to the nose, the nose is medial to the ears. - Proximal – Distal. Proximal means closer to the origin or point of attachment to the body, Distal means away from the point. Example: the knee is proximal to the foot, the foot is distal to the knee. - Superficial – Deep. Superficial means toward the body surface, Deep means toward the interior. Example: Skin is superficial to bone, bone is deep to skin.. There are also terms to describe the sectioning of the body and its organs into the three planes or dimensions of space (pp 14 – 16). A sagittal section divides into right and left parts. A frontal or coronal section divides into ventral and dorsal parts. A transverse section (usually called a cross section or Xsec.) divides into superior and inferior parts or cuts across a structure. 1 Pagination as in Marieb and Hoehn, Anatomy and Physiology, 3rd edition. 2 Specific areas of the body are described as regional terms or body landmarks (p 14). Among the more important regional terms are: Anterior Posterior Abdominal – anterior body trunk below ribs Cephalic – head Antecubital – anterior elbow Gluteal – buttocks Axillary – armpit Lumbar – back between ribs and hips Brachial – arm Occipital – posterior base of skull Buccal – cheek Popliteal – posterior knee Carpal – wrist Sacral – between the hips Cervical – neck Scapular – shoulder blade Coxal – hip Sural – posterior calf Deltoid – rounded part of shoulder Vertebral – spinal column Digital – fingers and toes Femoral – thigh Fibular – lateral calf Inguinal – groin Mammary – breast Manus – hand Nasal – nose Oral – mouth Orbital – bony eye socket Patellar – anterior knee Pelvic – below abdomen Pubic – genital area Sternal – breastbone Tarsal – ankle Thoracic – chest Umbilical – navel Spaces within the body are referred to as body cavities (pp 16 – 17). The two main body cavities are the dorsal cavity, which is divided into the cranial cavity (containing the brain) and the vertebral cavity (containing the spinal cord), and the ventral body cavity, which is divided into the thoracic cavity (containing the heart, lungs, bronchi, aorta) and the abdominopelvic cavity. The latter, in turn may be divided into the abdominal cavity (containing the stomach, small intestine, part of the large intestine, liver, gall bladder, spleen) and the pelvic cavity (containing the bladder, ♂prostate, ♀uterus, ovaries, rectum). The pelvic cavity is situated inferior to the pelvic brim (p 212). The abdominopelvic cavity is divided into four sections intersecting at the naval. These are the Right Upper, Right Lower, Left Upper and Left Lower Quadrants. The abdominal and thoracic cavities are divided by the diaphragm. Within the thoracic cavity is another cavity called the mediastinum containing the heart, bronchi and some major blood vessels. The ventral body cavity contains a thin double-layered membrane called the serosa or serous membrane. One layer, the parietal membrane lines the walls of the cavities and the other, the visceral membrane, covers the surface of the organs. Between these two serosa is a lubricating serous fluid. 3 II. The Chemistry of Life All matter is composed of different kinds of atoms called elements. There are 92 naturally occurring elements but we will concern ourselves with only a few of these in this course. Each element is written as a one or two letter symbol. We will be referring to the following in A & P: O = oxygen H = hydrogen C = carbon N = nitrogen P = phosphorous K = potassium Na = sodium Cl = chlorine Ca = calcium Fe = iron The different elements are determined by the different number of subatomic particles called protons found in their nuclei. Thus carbon always has six protons, oxygen eight, nitrogen seven and hydrogen only one. If you were to add a proton to carbon, for example, you would no longer have carbon – you would have nitrogen. Protons carry a positive electrical charge (+ ). Positively charged particles are attracted to negatively charged particles ( - ). Surrounding the nucleus of an atom are the negatively charged electrons. The number of electrons is equal to the number of protons in an electrically balanced atom. Sometimes an atom may gain or lose an electron. If it gains an electron, then the overall charge of the atom becomes negative and we would indicate the addition of one electron by a – sign. Example: Cl- . If the atom loses an electron, it becomes positive and we indicate this with a + sign. Example: Na+ . Charged particles are called ions. Note that hydrogen has only one proton and one electron. If hydrogen loses its electron (H+), it becomes a single proton. Another subatomic particle that we find in the nucleus is the neutron. Neutrons add mass (weight) to the atom but do not affect its charge. The atomic mass is the number of protons plus the number of neutrons in an atom. For example carbon is usually found in nature having 6 protons and 6 neutrons. The atomic weight is therefore 12 and we write this as 12C. But sometimes we find 13C and 14 C, indicating that carbon has 6 protons and 7 or 8 neutrons. These different forms of carbon are called isotopes. Molecules are combinations of atoms. A molecule of oxygen is usually found as two O atoms bound to one another. We write this as O2. If the atoms are made up of different elements we call this a compound, such as CH4 or H2O. The shape of the molecule is also important. Water, H2O, could be more accurately drawn as: _ O / \ H H + Although this water molecule is electrically balanced and not an ion, having as many electrons as protons, it is because of the shape that there is a positive end and a negative end of the molecule. This is called a polar molecule. Molecules may undergo chemical reactions, generally either synthesis reactions or decomposition reactions. Catalysts are chemical compounds that facilitate a chemical reaction but do not take part in the reaction itself. Biological catalysts are proteins called enzymes. 4 Chemical Bonds Atoms are closely connected to one another by chemical bonds that involve the electrons of the atoms. An ionic bond involves the transfer of one or more electrons from one atom to another. For example, Na transfers one of its electrons to Cl resulting in Na becoming + and the Cl becoming negative. The opposite charges attract one another so the two atoms become closely bound as the compound NaCl. Na+Cl- is a polar molecule. Covalent bonds occur when there is a sharing of electrons. We find that certain elements have a tendency to share a certain number of electrons. Hydrogen will share one (it only has one), oxygen 2, nitrogen 3 and carbon always wants to share 4 electrons. We can draw the simplest carbon compound as: H H – C– H We may also write this briefly as CH4 H The symbols – and indicate that the hydrogen is sharing its electron with the carbon and the carbon is sharing one of its electrons with the hydrogen. O=C=O (CO2) In the case of carbon dioxide, carbon shares two of its electrons with one oxygen and two other electrons with another oxygen. Each of the oxygens shares its two electrons with the carbon. These are called double bonds. A third type of bond is called a hydrogen bond and occurs with polar molecules. Water molecules are attracted to one another because the positive end of one molecule is attracted to the negative end of another molecule. + H \ O _ H / H \ + H O- H / \ O + H / Solutions are homogeneous mixtures of molecules. The molecules found in the greatest amount is called the solvent and that in the lesser amount is called the solute. Water is by far the most important biological solvent (our bodies are about half water). Molecules that readily dissolve in water are usually other polar compounds and are called hydrophilic (water loving) and those molecules that do not dissolve in water are called hydrophobic (water fearing). NaCl, being a polar molecule, dissolves readily in water. Hydrogen bonds pull the Na and Cl apart and the sodium and chloride ions dissociate in the water as they become dissolved. 5 pH Often H+ and OH- ions accumulate in solution. A measure of the concentration of these ions is the pH scale. This scale runs from 0 to 14. A pH of 7 is neutral, meaning there are just as many H+ as there are OH- ions. As you go down the scale towards 0, the concentration of H+ increases and the solution becomes more and more acidic. As the concentration of OH- ions increases from 7 to 14, the solution becomes more and more basic or alkaline. When the compound NaOH dissociates in water the OH- ions accumulate creating a base. When the compound HCl dissociates in water the H+ ions accumulate creating an acid. The pH scale is logarithmic so that a change of one unit represents a ten-fold increase or decrease in the concentration. III. Organic Chemistry We have already seen methane, the simplest of organic compounds where 4 hydrogen atoms share their electrons with a carbon atom. Compounds made only of carbon and hydrogen are called hydrocarbons. But carbon may not only share electrons with hydrogen but with other atoms including other carbons. H H | | H−C−C−H | | H H H H | | C─C / \ H ─ C C─ H \ / C─C | | H H H H H H | | | | H─C─C─C─C─H | | | | H H H H OR OR H H H H H H H H─C─C=C─C─C=C─C─H H H H Note that in all of the above examples, carbon is always sharing four electrons and hydrogen one. 6 We can substitute a hydrogen with what is called a functional group. Some of the more important functional groups that we see in biology are: O // ─ OH (hydroxyl group), ─ CH3 (methyl group), ─ C (carboxyl group), ─ NH2 (amino group) \ OH O ─ O ─ P ─ O (phosphate group) O The hydroxyl group on a chain of carbon atoms indicates an alcohol. H H H–C–C–H H OH (ethyl alcohol) The carboxyl group at the end of a chain indicates an organic acid. One of the hydrogens dissociates. O // H–C–C \ H O ⎯ … H+ (acetic acid) H IV. Important Biological Chemicals Carbohydrates Carbohydrates contain the elements Carbon, Hydrogen, and Oxygen approximately in the ratio of 1:2:1 (C6H12O6). Included in the carbohydrates are sugars or saccharides. Simple sugars or monosaccharides are ring structures: (pp 41 – 43) 7 (glucose) Glucose is made by green plants from carbon dioxide and water using the energy provided by the sun. H2O + CO2 → C6H12O6 + H2O Because glucose is such an important molecule from which organisms obtain energy, plants and animals will string together units of glucose called polysaccharides. Plants store glucose as a polysaccharide called starch. Animals store glucose in the liver and muscles as a polysaccharide called glycogen. To form a polymer, an H from one of the molecules and an OH from another are removed to form a molecule of water. This results in the two sugar molecules being chemically bound together. Long chains of sugars are called polysaccharides. ↓ H2O Polysaccharide 8 This type of chemical reaction, where a molecule of water is removed in order to join together two unit molecules such as glucose, is called dehydration synthesis. This reaction requires a specific enzyme to accomplish this as do most biochemical reactions. The opposite may also occur. Polymers may be split into their constituent monomers (unit molecules) by adding a molecule of water. This kind of chemical reaction is called hydrolysis. Hydrolysis occurs during the process of chemical digestion. Different enzymes must be used for this process. Proteins We can also join together and split apart other types of molecules by dehydration synthesis and hydrolysis. Amino acids (pp46 – 48) are compounds that have an amino group on one end and a carboxyl group (acid) on the other. H \ N–C–C / H H \ OH H O // This is glycine, the simplest amino acid. Other amino acids are formed by removing the encircled H and adding other organic All living things (almost) are based on the same 20 amino acids. H O // N– C– C / \ H H OH \ ↓ H2O H H O H H H H \ / H O // N –C– C \ H H OH O ETC. ─N─C─C─N─C─C– H H The covalent bond that binds two amino acids together is called a peptide bond. The polymer of amino acids that results from a series of dehydration synthesis reactions involving amino acids is called a polypeptide. Proteins are made of polypeptides but the terms are not synonymous. Proteins are polypeptides or combinations of polypeptides that have been folded to assume a particular shape. Proteins may be anywhere from about 100 to over 10,000 amino acids in length. 9 Although there are many structural proteins, most proteins are enzymes that facilitate the many chemical reactions that take place in our cells (pp 51 – 52). They speed up the rate of chemical reactions millions of times. The shape of the protein is extremely important. On each enzyme is an active site where the chemical reactants come together. If the shape is destroyed, the enzyme may no longer function. When a protein loses its shape, we say that it has been denatured. Such denaturing can be caused by heat and changes in pH. For example, egg white is almost pure protein. A fried egg is denatured protein. Sometimes enzymes must combine with certain organic or inorganic substances called cofactors before the enzyme becomes active. Some vitamins are enzymatic cofactors. The suffix “-ase” usually designates an enzyme. Lipids There are three important kinds of lipids in the body: steroids, fats (or triglycerides), and phospholipids (pp 44 – 46). Steroids are complex ring structures that are important for the formation of cholesterol and certain hormones. We will not go into their chemistry at this point. Fats are made from two components: one molecule of glycerol (an alcohol) and three molecules of various kinds of fatty acids. Glycerol is a 3-carbon molecule that has an hydroxyl group attached to each of the carbons. Fatty acids are long chains of hydrocarbons (sometimes over 20 carbons long) with a carboxyl group at one end (thus the “acid”). Again, by dehydration synthesis, an H from the glycerol and an OH from the fatty acid are removed (by enzymatic action) to form a molecule of H2O. H H H H –C — C — C– H O H O H O H OH \ → H2O C – CH2 – CH2 – CH2 – CH2 ….. CH2 – CH2 – CH3 // O When three of these fatty acids have been attached to the glycerol, the entire molecule is called a fat or triglyceride. (Look on page 45, Fig. 2.15 for a drawing of the triglyceride) Sometimes double bonds exist between carbons on the fatty acid chains. These are termed unsaturated fats, i.e. they don’t have as many Hydrogen atoms as possible. If the molecule contains several double bonds, it is called a polyunsaturated fat. When hydrogens are added to saturate those double bonds, the molecule is called a trans fat. These have recently been implicated to increase the risk of heart disease. Vegetable oil is unsaturated but is saturated with more hydrogen to create margarine and shortening. Phospholipids are molecules in which one of the long chain fatty acids has been replaced by a PO4 containing group. This gives the compound some unique properties. The PO4 containing group is polar and the two remaining carbon chains are non-polar. So one end is hydrophilic and one end is hydrophobic. 10 IV. Nucleic Acids There are two kinds of nucleic acid molecules – DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Let’s consider DNA first. A 5-carbon sugar called deoxyribose forms long chains. Each sugar unit is connected to the next by a phosphate. Two of these long chains exist parallel to each other. (There is a carboxyl group at one end – hence the acid.) Each of the sugar units is also bound to one of four nitrogenous bases. These bases are called Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). Nitrogenous bases are also paired so that A on one chain is always bound to T on the opposite chain. And G is always bound to C. (pp 52 – 54) It may be drawn like this: (“D’s” represent the sugar units.) / \ PO4 PO4 \ / D─T…A─D / \ PO4 PO4 \ / D─C…G─D / \ PO4 PO4 \ / D─A…T─D / \ PO4 PO4 \ / D─C…G─D / \ PO4 PO4 \ / D─G…C─D / \ PO4 PO4 \ / D─G…C─D / \ ETC. These Chains may continue for thousands of base pairs. The order in which the base pairs occur is very important. The two chains are then twisted around one another to form a double helix. DNA is the material of heredity and occurs chiefly in the nucleus of the cell. RNA is similar to DNA but with a number of important differences. 1. There is no Thymiee in RNA. Instead A is bound to another base called Uracil (U). 2. The sugar Ribose is substituted for Deoxyribose. (There is one fewer O atom in Ribose.) 3. RNA is single stranded. 11 Another important biological molecule based on nucleic acid is Adenosine Triphosphate or ATP. This molecule provides the energy for many of the chemical reactions that occur in the cell. It consists of one molecule of ribose bound to adenine on one end and to three phosphate groups on the other. (pp 54 – 55) Adenine – Ribose – PO4 – PO4 ~PO4 ↑ high energy bond The final phosphate is released by ATP and transferred to another molecule. The energy transferred to this so-called phosphorylated molecule allows for much of the cell’s metabolism. 12