Bio Final PDF - Human Anatomy

Anatomical terms ​ In physiology, standard terms are used when referring to anatomical parts of humans ​ They always refer to a body that is in the upright, standing position ○​ Ventral or anterior refers to the front ○​ Dorsal or posterior means toward the back...

Anatomical terms ​ In physiology, standard terms are used when referring to anatomical parts of humans ​ They always refer to a body that is in the upright, standing position ○​ Ventral or anterior refers to the front ○​ Dorsal or posterior means toward the back ○​ Superior means toward the head ○​ Inferior means toward the feet Anatomical terms ​ Some are relative to other body parts ○​ Something that is medial is closer to the midline of the body ○​ Lateral is away from the midline ​ When referring to an appendage like an arm, fingers, or a leg: ○​ Proximal means closer to the trunk of the body ○​ Distal means away from the trunk Organ systems ​ Organ system: A set of organs that interacts to carry out a major body function ​ Organ: Body structure that integrates different tissues and carries out a specific function ​ Organ - a group of tissues performing a common function ​ Groups of organs with a similar function form an organ system ​ Some of these organ systems (for example, the respiratory system) occupy specific cavities; others (for example, the muscular system) are found throughout the body ​ Organs and cavities are lined with membranes, many of which secrete fluid ​ Thirteen organ systems make up the human body ​ Organ systems work together in the body ​ Some organs are involved in the function of more than one organ system ​ E.g.: the pancreas plays a role in the endocrine and digestive systems ​ Other structures and glands also contribute to the operation of organ systems (accessory) Body cavities ​ Ventral cavity (or coelom in early development) ○​ Contains the thoracic, abdominal, and pelvic cavities ○​ The diaphragm separates the thoracic and abdominal cavities ○​ Males have an external extension of the abdominal wall called the scrotum, which contains the testes ​ Dorsal cavity ○​ Contains the cranial cavity and vertebral canal Organs in ventral cavity ​ The thoracic cavity contains the lungs and heart ​ The abdominal cavity contains the stomach, liver, spleen, pancreas, gallbladder, most of the small and large intestines, and kidneys ​ The pelvic cavity contains the rectum, the urinary bladder, the internal reproductive organs, and the rest of the small and large intestines Body membranes ​ Body membranes line cavities and the internal spaces of organs and tubes that open to the outside ​ Four types: mucous, serous, and synovial membranes and the meninges ​ Mucous membranes ○​ Line the tubes of the digestive, respiratory, urinary, and reproductive systems ○​ Composed of epithelium overlying loose fibrous connective tissue ○​ Contains goblet cells that secrete mucus ​ Serous membranes ○​ Line closed cavities (not open to the environment) and cover the surface of the organs contained within ○​ That is, pleurae line the thoracic cavity and cover the lungs ○​ That is, pericardium forms the pericardial sac and covers the heart ○​ That is, double layer of peritoneum, called mesentery, lines the abdominal cavity and covers its organs ​ Synovial membranes ○​ Composed only of loose connective tissue ○​ Line freely moveable joints ○​ Secrete synovial fluid for lubrication ​ Meninges (sing., meninx) ○​ Composed only of connective tissue ○​ In the dorsal cavity (around the brain and spinal cord) ○​ Meningitis—inflammation of the meninges Integumentary system ​ Outer protective layer  ​ Includes the skin and accessory organs such as hair, nails, and glands ​ Functions: ○​ Protects underlying tissues from trauma, pathogen invasion, and water loss ○​ Helps regulate body temperature ○​ Contains sensory receptors, such as touch and temperature receptors ○​ Makes us aware of our surroundings ​ Contains all four tissue types ​ Skin has two main regions: the epidermis and the dermis ​ Under the skin there is a subcutaneous layer (hypodermis) Regions of the skin ​ The skin has two regions: ○​ Epidermis and dermis ​ The subcutaneous layer, or hypodermis, is between the skin and any underlying structures, such as muscle or bone Anatomy of human skin The epidermis ​ Thin, outermost layer of the skin ​ Made of stratified squamous epithelium ​ Stem cells that produce new epidermal cells are in the deepest layer ○​ If an injury destroys the stem cells, skin needs to be replaced ​ Autograft - from another area of the body ​ Allograft - from another person ​ Can also grow skin in the lab ​ Stem cells can give rise to different types of specialized cells ○​ Growing replacement tissues Cells of the epidermis ​ Keratinocytes - in the upper layers of epidermis ○​ Dead and filled with keratin ○​ Forms a waterproof barrier ​ Langerhans cells - a type of white blood cell ​ Melanocytes - produce melanin ○​ Produces skin color and protects from UV light ○​ People have the same number of melanocytes, but the amount of melanin produced varies ​ Other contributors to skin color: carotene and hemoglobin ​ Epidermal cells produce vitamin D when exposed to UV rays ○​ Vitamin D is important in the regulation of calcium and phosphorus levels in the body The dermis and the subcutaneous layer ​ The Dermis ○​ Thick, inner layer of the skin ○​ Made of dense fibrous connective tissue ○​ Contains collagen and elastic fibers for strength and elasticity ○​ Contains blood vessels, sensory receptors, and glands ○​ Sensory receptors are specialized for touch, pressure, pain, hot, and cold ​ The subcutaneous layer ○​ Technically not part of the skin ○​ Composed of loose connective tissue and adipose tissue ○​ Stores energy, insulates, and protects Accessory organs of the skin - nails, hair, and glands ​ Nails ○​ Offer a protective covering of the digits (fingers and toes) ○​ Nails grow from the nail root to cover the nail bed ○​ The cuticle covers the nail root ○​ Lunula - white half-moon shape at the base ​ Hair ○​ Hair follicles - epidermal structures that surround the hair itself ○​ Hair shaft - the portion of hair protruding from the skin ○​ The color of hair comes from melanin; as melanocytes age, they produce less pigment and hair turns gray ○​ Arrector pili muscles - attached to the hair follicle - Can contract, which creates “goosebumps” ​ Oil glands (sebaceous glands)  ○​ Produce sebum, which softens the hair and skin ○​ It also retards bacterial growth ○​ Acne - inflammation of the sebaceous glands ​ Sweat glands (sudoriferous glands) ○​ In the dermis; their ducts open onto the skin surface ○​ Help to regulate body temperature Overview of the cardiovascular system ​ Made up of the heart and blood vessels ​ The heart pumps blood through blood vessels ○​ It brings nutrients to cells and helps get rid of wastes ○​ Exchange of substances occurs through interstitial fluid Cardiovascular system circulation ​ Circulation allows for the exchange of materials ○​ The cardiovascular system works with all other organ systems ○​ Thousands of miles of blood vessels move the blood and its contents to and from all organs ​ Gas exchange ○​ Working with the respiratory system, blood drops off carbon dioxide and picks up oxygen at the lungs ​ Nutrient exchange ○​ Working with the digestive system, nutrients enter the bloodstream at the intestines, transporting the much-needed substances to the body’s cells ○​ Works with the liver, supporting metabolism, detoxification, and homeostasis ○​ At the kidneys, the blood is purified, and water and Functions of the cardiovascular system ​ Transport: oxygen, carbon dioxide, waste products, nutrients, hormones, and immune system cells ○​ Immune system cells and their associated antibodies and chemical signals help protect the body from infection ​ Homeostasis: plays a central role in maintaining homeostasis (a constant environment) for various internal conditions ○​ E.g.: temperature, pH balance, water, electrolyte levels The heart ​ The heart is a double pump ​ Located between the lungs; points toward the left hip ​ Consists mostly of the myocardium, which is made of cardiac muscle tissue ○​ Muscle fibers are branched and connected by intercalated discs, which contain gap junctions ​ These allow cells to contract in unison  ○​ Also connected by desmosomes, a type of cell junction that prevents overstretching by holding adjacent cells together ​ Surrounded by a sac called the pericardium, which secretes pericardial fluid for lubrication ​ Internally, the septum divides the heart into right and left sides ​ Consists of 4 chambers: ○​ 2 upper atria (sing., atrium) and 2 lower ventricles ​ Two types of valves: semilunar valves and atrioventricular (AV) valves ○​ The AV valves are reinforced by chordae tendineae ○​ Left AV valve—bicuspid, or mitral valve ○​ Right AV valve—tricuspid valve ○​ Semilunar valves: pulmonary valve and aortic valve Coronary circulation: The heart’s blood supply ​ The myocardium needs its own blood supply ​ Coronary arteries supply it ​ They are the first branches off the aorta ​ Coronary veins drain it ​ Empty into the right atrium ​ Coronary artery disease - blockage in the coronary arteries causes a myocardial infarction (heart attack) Passage of blood through the heart - right side ​ The inferior and superior vena cava carry O2-poor, CO2-rich blood from systemic veins to the right atrium ​ The right atrium contracts, sending blood through the right AV (tricuspid) valve into the right ventricle ​ The right ventricle pumps blood through the pulmonary valve into the pulmonary trunk, which branches into right and left pulmonary arteries ○​ They lead to the lungs Passage of blood through the heart - left side ​ The pulmonary veins carry O2-rich, CO2-poor blood from the lungs to the left atrium ​ Blood then flows through the left AV (bicuspid) valve into the left ventricle ​ The left ventricle pumps blood through the aortic valve into the aorta ​ The aorta branches into smaller arteries, which lead to arterioles, then capillaries, venules, veins, and back to the vena cavae Structure and function details ​ The walls of the left ventricle are thicker than the right ventricle because it must pump blood to the entire body, not just to the lungs  ​ The walls of atria are thinner than ventricles ​ Pulmonary capillaries within the lungs allow gas exchange ○​ Oxygen enters the blood; carbon dioxide waste is excreted from the blood ​ Valves ensure the direction of blood flow The cardiac cycle ​ The order of events in the cardiac cycle: ○​ First the atria contract together ○​ Then the ventricles contract together ○​ Then the heart relaxes ​ Systole - heart contraction ​ Diastole - heart relaxation ​ Occurs 70 times per minute on average ○​ There are two audible sounds: “lub-dub” ○​ Lub: from the closure of the AV valves ○​ Dub: from the closure of the semilunar valves Internal (intrinsic) conduction system ​ The SA node in the right atrium initiates the heartbeat by sending out an electrical signal; this causes the atria to contract ○​ SA node is called the pacemaker ​ This impulse reaches the AV node, also in the right atrium ○​ AV node sends a signal down the AV bundle and Purkinje fibers; this causes ventricular contraction ​ These impulses travel through gap junctions in the intercalated discs External (extrinsic) control of heartbeat ​ The cardiac control center in the brain increases or decreases the heart rate depending on the body’s needs ​ Some hormones increase heart rate Electrocardiogram (ECG) ​ An electrocardiogram is a record of the heartbeat ○​ A recording of the electrical changes in the heart muscle during a cardiac cycle ​ The atria produce an electrical current, called the P wave, when stimulated by the SA node ​ QRS complex - wave of electrical current traveling through the ventricles ○​ Signals that the ventricles are about to contract ​ The recovery of the ventricles is represented as the T wave ​ Detects abnormalities ​ E.g.: ventricular fibrillation - caused by uncoordinated, irregular electrical signals in the ventricles ​ The heart can’t pump blood; tissues become starved of oxygen  ​ Defibrillation - applying a strong electrical signal to reset the heart; hopefully, the SA node will start firing again The types of blood vessels ​ There are three types of blood vessels that transport blood to and from the tissues of the body: ○​ Arteries ○​ Veins ○​ Capillaries The arteries: from the heart ​ Artery ○​ Carries blood away from the heart ○​ Their walls have three layers: ○​ Endothelium (Tunica intima) - the thin, inner epithelium ○​ Middle layer (Tunica media) - smooth muscle and elastic tissue ○​ Allows arteries to expand and recoil ○​ Outer layer (Tunica adventitia)- connective tissue ​ Arterioles ○​ Small arteries ○​ Middle layer has mostly smooth muscle ○​ It contracts to constrict the vessel, reducing blood flow and raising blood pressure ○​ When relaxed, the vessel dilates, increasing blood flow and reducing blood pressure The capillaries: sites of exchange ​ Microscopic vessels between arterioles and venules ​ Walls of capillaries are made only of endothelium ​ Form capillary beds where gas, nutrient, and waste exchange occurs ​ Have precapillary sphincters, which control blood flow through the capillary bed ​ When closed, blood instead flows through an arteriovenous shunt Exchange at the capillaries ​ Two forces drive fluid in and out of capillaries: ○​ Blood pressure drives fluid out of the capillary, mainly at the arterial end of the capillary bed ​ This fluid contains everything that blood contains except cells and plasma proteins  ○​ Osmotic pressure draws water into the capillary by osmosis, mostly at the venule end ​ Some tissue fluid enters lymphatic capillaries and becomes lymph, which is eventually returned to the cardiovascular system Movement of fluid into lymphatic vessels ​ Heart’s pumping action puts pressure on blood ​ Causes small amounts of water and some proteins to move into extracellular fluid ​ Network of drainage vessels pick up excess fluid ○​ Part of lymphatic system ​ Lymphatic system ○​ The lymphatic system works with the immune system and assists the cardiovascular system by collecting excess interstitial fluid and returning it to the blood ○​ When fluid enters the lymphatic vessels, it is called lymph Precapillary sphincter ​ Regulates blood flow into the capillary ​ Made of smooth muscle that can contract and relax The veins: to the heart ​ Venules - small veins that receive blood from the capillaries ​ Veins carry blood toward the heart ​ Venule and vein walls have the same three layers as arteries, but less smooth muscle in the middle layer ​ Veins that carry blood against gravity have valves to keep blood flowing toward the heart ​ Walls of veins are thinner than arteries so they can expand to hold more blood ○​ At any one time, they store 70% of the blood ​ If blood is lost (that is, hemorrhage), the nervous system causes the veins to constrict to increase blood volume Blood pressure and pulse ​ Blood Pressure - the pressure that blood exerts against a blood vessel wall ○​ Is highest in the aorta, right next to the heart ○​ It progressively decreases as blood moves through the body's vessels - arteries, arterioles, capillaries, venules, and finally, the veins ○​ Is lowest in the superior and inferior venae cavae, which enter the right atrium ​ Pulse (heart rate) - surge of blood into an artery causes the walls to stretch, and then recoil ○​ Usually measured in the radial artery at the wrist or carotid artery in the neck ○​ A measurement of the heart rate; averages 60 - 80 beats per minute Regulation of blood pressure ​ Blood pressure moves blood in arteries ​ Contraction of ventricles creates blood pressure, which propels blood through the arteries ​ Measured with a sphygmomanometer, in the brachial artery of the arm ​ Systolic pressure - the highest pressure; when blood is ejected from the heart ​ Diastolic pressure - the lowest pressure; when the ventricles relax ​ Average is 120/80 mmHg (systolic/diastolic) Values for adult blood pressure Blood velocity and pressure in the blood vessels ​ Blood flow is regulated ​ Blood flow is slow in the capillaries ​ Blood pressure decreases as it flows away from the heart ○​ Blood flow is slowest in the capillaries to increase the exchange of gases, nutrients, and wastes ○​ Blood pressure is adjusted by the precapillary sphincters Blood flow in veins ​ Blood flow in veins returns blood to heart ​ Blood pressure is very low in the veins, so doesn’t contribute much to the movement of blood ​ Venous return is dependent on three additional factors: ○​ Skeletal muscle pump (dependent on skeletal muscle contraction) ○​ Respiratory pump (dependent on breathing) ○​ Valves present in veins Homework 1.​ Label the heart (chambers, blood vessels, valves etc.) and explain the blood flow through the heart in your own words. As you explain, make sure to use the anatomical words. 2.​ On this diagram draw exchange of material across the capillaries and explain in your own words. Cardiovascular Pathways ​ Blood flows in two circuits: the pulmonary circuit and systemic circuit ​ Pulmonary circuit circulates blood through the lungs ​ Systemic circuit circulates blood through the body tissues Pulmonary circuit Pulmonary circuit ​ Right atrium pumps deoxygenated blood into the right ventricle, which pumps it into the pulmonary trunk ​ The pulmonary trunk splits into right and left pulmonary arteries, which go to the lungs ​ In the lungs, the pulmonary arteries branch into arterioles, which lead to capillaries ​ This is where gas exchange occurs ​ The pulmonary capillaries lead to venules, which merge into the pulmonary veins ​ The four pulmonary veins empty into the left atrium ​ The pulmonary arteries carry oxygen-poor blood; the pulmonary veins carry oxygen-rich blood The systemic circuit ​ The left ventricle pumps blood into the aorta, which gives off branches to all the tissues of the body ​ Arteries branch into (eventually) arterioles, which lead to capillaries ​ Capillaries lead to venules, which drain into veins, which lead to the superior and inferior vena cavae ​ The vena cavae empty into the right atrium The systemic circuit: exchanges with interstitial fluid ​ Usually, blood flows from the aorta into an artery that supplies an organ, then through veins back to one of the vena cavae (sing., vena cava) ○​ Aorta > renal artery > kidney > renal vein > inferior vena cava ​ However, there are special routes that don’t follow this pathway ○​ The hepatic portal system Hepatic portal system: Specialized for blood filtration ​ Brings nutrient-rich blood from the digestive tract to the liver ​ The liver synthesizes blood proteins from the amino acids in the hepatic portal vein and stores the glucose as glycogen ​ The liver also removes toxins and pathogens that enter the blood through the digestive system ​ Blood is drained from the liver into the hepatic veins, which drain into the inferior vena cava Cardiovascular disease ​ Leading cause of early death in Western countries Hypertension (high blood pressure) ​ A systolic pressure of 140 or greater or a diastolic pressure of 90 or greater ​ A “silent killer” because there are few symptoms until it causes kidney failure, a heart attack, or stroke ​ Treated with diuretics, which increases the production of urine, and other drugs Atherosclerosis ​ A buildup of atherosclerotic plaque in the walls of blood vessels ​ Plaques narrow blood vessel diameter, decreasing blood supply to tissues ​ Can cause clots to form in the roughened walls of arteries ○​ Thrombus - a clot that is stationary ○​ Embolus - a clot that detaches and moves to distant sites ○​ Thromboembolism - an embolus that has become lodged in a blood vessel Heart failure ​ The heart no longer pumps properly ​ Treatments: ○​ Wrapping the heart to prevent enlargement ○​ Implantable cardioverter-defibrillator (ICD) corrects an irregular rhythm ○​ Heart transplant ○​ Injection of stem cells to repair damaged heart ○​ Left ventricular assist device (LVAD)—battery-powered pump to assist the heart ○​ Total artificial heart (TAH)—temporary solution Overview of the digestive system ​ The organs are located within the gastrointestinal (GI) tract ​ Function - to hydrolyze, or break down, the macromolecules found in food ​ The subunit molecules (monosaccharides, amino acids, fatty acids, and glycerol) can cross plasma membranes using facilitated and active transport ​ The nutrients made available are transported by the blood to our cells Processes of digestion ​ Ingestion - intake of food via the mouth ​ Digestion - mechanically or chemically breaking down foods into their subunits ○​ Mechanical digestion - chewing in the mouth and contractions of smooth muscles in the stomach ○​ Chemical digestion - digestive enzymes hydrolyze macromolecules into subunits ​ Begins in the mouth, continues in the stomach, and is completed in the small intestine ​ Movement - food is passed from one organ to the next, normally by contractions of smooth muscle called peristalsis; indigestible must be expelled ​ Absorption - movement of nutrients across the GI tract wall into the blood; they are then delivered to cells ​ Elimination - removal of indigestible wastes ○​ Defecation Wall of the digestive tract ​ Lumen - open area of a hollow organ or vessel; in the GI tract, it contains food or feces ​ Layers: ○​ Mucosa - innermost layer; produces mucus for protection; also produces digestive enzymes  ○​ Submucosa - loose connective tissue; contains blood vessels, lymphatic vessels, and nerves ○​ Muscularis - made of two layers of smooth muscle (inner, circular layer, and an outer, longitudinal layer) that move food along the GI tract ○​ Serosa - outer lining; is part of the peritoneum The pharynx and esophagus ​ The mouth and nasal passages lead to the pharynx ​ In turn, the pharynx opens into both the food passage (esophagus) and air passage (trachea, or windpipe) ○​ These two tubes are parallel to each other; the trachea is in front of the esophagus ○​ The esophagus is a muscular tube that leads to the stomach Swallowing ​ Starts off voluntary, but once food or drink is pushed back into the pharynx, it becomes an involuntary reflex ​ Food normally enters the esophagus because other possible avenues are blocked ○​ The soft palate moves back to close off the nasal passage, and the trachea moves up under the epiglottis to cover the glottis, the opening to the larynx Peristalsis ​ Peristalsis - contractions that push food through the digestive tract ​ Sphincter - a ring of muscle that acts as a valve ​ When it contracts, it stops food from moving through; when it relaxes, it allows food through ​ That is, the lower esophageal sphincter is between the esophagus and the stomach ○​ Heartburn - failure of this sphincter; stomach contents move from the stomach into the esophagus ​ Vomiting - when strong contractions of the abdominal muscles and the diaphragm (the muscle separating the thoracic and abdominal cavities) force the contents of the stomach into the esophagus and oral cavity The stomach ​ Stores food, starts digestion of proteins, and controls movement of food into the small intestine ​ Does not absorb nutrients ○​ However, it does absorb alcohol, because alcohol is fat-soluble and can pass through membranes easily  ​ There are three layers of muscle in the muscularis layer (instead of two) to help in mechanical digestion ○​ Circular, longitudinal, and third oblique layer The stomach ​ The mucosa has deep folds called rugae and gastric pits, which contain gastric glands ​ The gastric glands produce gastric juice, which contains: ○​ Pepsin - digests proteins ○​ Hydrochloric acid (HCl) - pH of 2 ​ Kills bacteria and activates pepsin ​ Mucus ​ Normally, the stomach empties in 2 - 6 hours ​ Chyme - a mixture of food and gastric juice ○​ Pyloric sphincter - allows only a small amount of chyme to enter the small intestine at a time The small intestine ​ The small intestine is the main digestive organ ​ Named for its small diameter compared with the large intestine’s ​ The small intestine is very long, longer than the large intestine ○​ Averaging about 6 m (18 ft) in length, whereas the large intestine is about 1.5 m (4.5 ft) ​ It consists of three regions: ○​ Duodenum ○​ Jejunum ○​ Ileum ​ Nutrients are absorbed in the small intestine ​ The mucosa contains fingerlike projections called villi (sing., villus) ​ The cells that cover the villi have microvilli ○​ Give the villi a fuzzy “brush border” ○​ Contain brush border enzymes that complete digestion ​ These two structures greatly increase the surface area of the small intestine for absorption of nutrients ​ Nutrients are absorbed into the villi, which contain blood capillaries, and a small lymphatic capillary called a lacteal ​ Monosaccharides and amino acids enter the blood capillaries of a villus ​ Glycerol and fatty acids form lipoprotein droplets called chylomicrons, which then enter a lacteal  ​ After nutrients are absorbed, they are eventually carried to all the cells of the body by the blood The large intestine ​ Large intestine - includes the cecum, the colon, the rectum, and the anal canal ​ Larger in diameter than the small intestine, but it is shorter in length ​ Cecum - the first portion ○​ Vermiform appendix - projection off of the cecum ​ Fights infections ​ Appendicitis - inflamed appendix; can cause peritonitis, a life-threatening infection of the peritoneum ​ Colon - includes the ascending colon, which goes up the right side of the body; transverse colon, which crosses the abdominal cavity; descending colon, which passes down the left side; and the sigmoid colon, which enters the rectum, the last portion of the large intestine ○​ The rectum opens at the anus, where defecation, the expulsion of feces, occurs Functions of the large intestine ​ Does not produce digestive enzymes ​ Does not absorb nutrients except certain vitamins ​ Absorbs water from feces to prevent dehydration ​ Absorbs vitamins produced by intestinal flora, the bacteria that inhabit the intestine ​ Bacteria break down indigestible material and produce B-complex vitamins and vitamin Forms feces ○​ ¾ water, ¼ solid wastes ○​ Bacteria and dietary fiber (indigestible remains) make up the solid wastes ○​ Bacteria digesting the indigestible materials causes the odor of feces and accounts for the gas ○​ Stercobilin, a breakdown product of bilirubin, and oxidized iron cause the brown color of feces ​ Defecation - ridding the body of feces ○​ Peristalsis forces feces into the rectum ○​ Stretching of the rectal wall initiates nerve impulses to the spinal cord ○​ Then the rectal muscles contract and the anal sphincters relax, allowing the feces to exit the body through the anus ○​ Can inhibit defecation by contracting the external anal sphincter, which is made of skeletal muscle Homework ​ Explain what ordinarily prevents food from entering the nose or trachea when you swallow. ​ Describe the functions of the stomach and how the wall of the stomach is modified to perform these functions.  ​ Detail the functions of the small intestine and how the wall of the small intestine is modified to perform these functions. ​ Summarize the differences in how carbohydrates, proteins, and fats are digested and absorbed by the small intestine. ​ Describe the parts of the large intestine and provide the function for each. ​ Explain the role of the large intestine in the digestive tract. ​ Describe how constipation and diarrhea are related to the large intestine. Digestive system – an overview Digestive system has two main components What are accessory organs? ​ Accessary glands are not part of the digestive tract, but they have a role in digestive activities ○​ Physical or chemical breakdown of food Mouth (oral cavity) ​ Receives food and begins mechanical and chemical digestion ​ The roof of the mouth separates the nasal cavity from the oral cavity ○​ Two parts: a bony hard palate and a soft palate ​ The soft palate is made of muscle; ends in the uvula ​ Tonsils ○​ In the back of the mouth on either side of the tongue ○​ Lymphatic tissue; help protect from disease ○​ There is a single pharyngeal tonsil in the nasopharynx, commonly called the adenoids ​ Tongue ○​ Covered in taste buds  ○​ Assists in mechanical breakdown, movement of food ○​ Forms a bolus (mass of chewed food) and moves it toward the pharynx Teeth ​ Mechanically digest food ​ 20 smaller deciduous (baby) teeth, 32 adult teeth ​ Two main divisions: ○​ Crown - the part of the tooth above the gum line ○​ Root - the portion below ​ Enamel - extremely hard outer layer ​ Dentin - a thick layer of bonelike material ​ Pulp - nerves and blood vessels ​ Periodontal membranes - anchor the tooth to the jawbone Salivary glands ​ Three pairs of salivary glands secrete into the oral cavity ○​ Parotid salivary gland ○​ Sublingual salivary gland ○​ Submandibular salivary gland ​ Secrete saliva ○​ Lubricate the mouth ○​ Dissolve chemicals that can stimulate taste buds ○​ Antibacterial enzyme ​ Lysozyme ○​ Begin the digestion of complex carbohydrates ​ Salivary amylase Structure and organizations of the pancreas ​ Lies posterior to the stomach ​ Extends laterally from the duodenum toward the spleen ​ Most pancreatic cells produce pancreatic juice, which enters the duodenum via the pancreatic duct ○​ Secretes digestive enzymes ○​ Secretes bicarbonate ion (HCO3-)-rich fluid which neutralizes chyme as it enters small intestine Functions of the pancreas ​ Hormones secreted by the duodenum controls the secretion of pancreatic juice ○​ Secretin – pancreatic secretion of watery buffer (pH 7.5 – 8.8)  ○​ Cholecystokinin – production and secretion of pancreatic enzymes ​ What enzymes are included in the pancreatic juice? ○​ Pancreatic alpha amylase – breaks down starches ○​ Pancreatic lipase – breaks down complex lipids and releases fatty acids ○​ Nucleases – breaks down RNA and DNA ○​ Proteolytic enzymes – breaks down proteins ​ Proteases ​ Peptidases The liver ​ The largest visceral organ/gland ​ Left lobe and the right lobe ​ Lies mainly in the upper right abdominal cavity, under the diaphragm ​ Composed of liver lobules (structural and functional units) ​ Produce bile ○​ Bile - contains bicarbonate ions (neutralize acids), cholesterol, phospholipids, organic wastes and bile salts ​ Gallbladder ○​ Stores bile and secretes it during a meal ○​ People lacking a gallbladder can digest fat, but may need to limit how much is eaten at once Organization of liver lobules The liver and the pancreas Hepatic circulation ​ Hepatic artery ○​ Derived from the aorta to bring oxygenated blood to the liver ​ Hepatic vein ○​ Take deoxygenated blood away from the liver and empties into the inferior vena cava ​ Hepatic portal vein ○​ Brings nutrient-rich blood toward the liver from the small intestine Functions of the liver ​ The liver carries out more than 200 functions! Functions of the liver Hormonal control and regulation of digestion ​ Secretion of digestive juices is controlled by the nervous system and digestive hormones ​ When you look at or smell food, the parasympathetic nervous system stimulates gastric secretion ​ A meal rich in protein causes the stomach to produce the hormone gastrin ○​ Increases the secretory activity of gastric glands  ​ Secretin - secreted by the duodenum ○​ Release is stimulated by HCl (present in chyme) ​ Cholecystokinin (CCK) - secreted by the duodenum when proteins and fat are present ○​ Causes the liver to increase production of bile and causes the gallbladder to contract and release stored bile ○​ These hormones increase the production of pancreatic juice Heartburn (GERD) ​ The lining of the esophagus is thinner than the lining of the stomach; if chyme enters the esophagus, it produces a burning sensation ​ Can be caused by pregnancy and excess fat pushing on the stomach ​ Gastroesophageal reflux disease (GERD) - chronic heartburn Diverticulosis ​ A condition in which the mucosa of any part of the GI tract (usually the large intestine) pushes through the other layers and forms pouches where food collects ​ Diverticulitis - when the pouches become infected ​ This happens in 10 - 25% of people with diverticulosis Bowel disease ​ Inflammatory bowel disease (IBD) - chronic diarrhea, abdominal pain, fever, and weight loss ○​ An inflammatory condition ​ Irritable bowel syndrome (IBS) - contractions of the muscularis cause abdominal pain, constipation, and diarrhea ○​ A set of symptoms; no inflammation ○​ Most common intestinal disorder ○​ Symptoms include abdominal pain and alternating diarrhea and constipation ○​ The underlying cause is not known Inflammatory bowel disease (IBD) ​ Ulcerative colitis ○​ Affects the large intestine and rectum ○​ Results in diarrhea, rectal bleeding, abdominal cramps, and urgency to defecate ​ Crohn’s disease ○​ Usually in the small intestine ○​ Ulcers in the intestinal wall; they are painful and bleed as they erode the submucosal layer, where there are nerves and blood vessels ○​ Can’t absorb nutrients in the affected areas  ○​ Symptoms: diarrhea, weight loss, abdominal cramping, anemia, bleeding, and malnutrition Polyps and cancer ​ Polyps - small growths in the colon lining ​ Can be benign or cancerous ​ If colon cancer is detected while still confined to a polyp, the expected outcome is a complete cure ​ Increased dietary fat raises the risk of colon cancer ​ Fiber in the diet inhibits colon cancer, and regular elimination reduces the time that the colon wall is exposed to cancer-promoting agents in the feces Malabsorption disorders ​ Lactose intolerance ○​ Lactose is the primary sugar in milk ○​ Lactase - the brush border enzyme that digests lactose ○​ Characterized by diarrhea, gas, bloating, and abdominal cramps after ingesting milk and other dairy products ​ Diarrhea occurs because the undigested lactose causes fluid retention in the small intestine ​ Gas, bloating, and cramps occur when bacteria break down the lactose anaerobically ​ Celiac Disease ○​ Autoimmune response against a protein called gluten, which is naturally found in grains such as wheat, barley, and rye ○​ The presence of gluten in the small intestine results in an inflammatory response, which damages the villi and microvilli of the small intestine ○​ Can lead to abdominal pain, diarrhea, and malnutrition Liver diseases ​ Hepatitis ○​ Inflammation of the liver ○​ Has different forms ○​ Hepatitis A - usually acquired from sewage-contaminated drinking water and food ○​ Hepatitis B - usually from sexual contact, but also from blood transfusions or contaminated needles ​ More contagious than the AIDS virus and is spread in the same way ​ Vaccines are available for hepatitis A and B ○​ Hepatitis C - usually acquired by infected blood ​ Can lead to chronic hepatitis, liver cancer, and death Liver diseases ​ Cirrhosis  ○​ Chronic disease; first, liver becomes fatty, and then filled with fibrous scar tissue ○​ Often seen in people with obesity and alcohol use disorder, due to malnutrition and the excessive alcohol (a toxin) the liver is forced to break down ○​ The liver can regenerate and recover if the rate of regeneration exceeds the rate of damage ​ During liver failure there may not be enough time to let the liver heal so will need a liver transplantation The respiratory system ​ Ensures that oxygen enters the body and carbon dioxide leaves the body ​ During inspiration, or inhalation, air moves from the atmosphere to the lungs through cavities and tubes ​ During expiration, or exhalation, air moves from the lungs to the atmosphere via the same structures ​ Ventilation (breathing) - inspiration and expiration ○​ Depends on the cardiovascular system to transport oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs ○​ During cellular respiration, cells use up oxygen and produce carbon dioxide The respiratory system and homeostasis ​ Ways the respiratory system works with the cardiovascular system to maintain homeostasis: ○​ External respiration, the exchange of gases (oxygen and carbon dioxide) between air and the blood ○​ Transport of gases to and from the lungs and the tissues ○​ Internal respiration, the exchange of gases between the blood and tissue fluid ​ Blood supply to the airway: Bronchial artery and bronchial vein The upper respiratory tract ​ The nasal cavities ​ The pharynx ​ The larynx The nose ​ The nose opens at the nares (nostrils), which lead to the nasal cavities ​ The nasal cavities are separated from each other by a septum  composed of bone and cartilage ​ Hairs filter the air and trap small particles, so they don’t enter air passages ​ Lined with mucous membrane ○​ The mucus helps trap particles and move them to the pharynx, where they can be swallowed or expectorated ​ Under the mucous layer is the submucosa, which contains lots of capillaries that help warm and moisten the incoming air ​ The abundance of capillaries makes us susceptible to nosebleeds ​ Contain odor receptors (olfactory receptors) ​ Tear glands in the eye drain into the nasal cavities by way of tear ducts ○​ Crying causes a runny nose ​ The nasal cavities also connect with the sinuses of the skull ○​ Fluid may accumulate in these sinuses, causing an increase in pressure, sinus headache ​ Air in the nasal cavities passes into the nasopharynx, the upper portion of the pharynx ​ Auditory tubes (eustachian tubes) connect the nasopharynx to the middle ear ○​ When air pressure inside the middle ears equalizes with the air pressure in the nasopharynx, the auditory tube openings may create a “popping” sensation The pharynx and larynx ​ The pharynx (throat) - funnel-shaped cavity that connects the nasal and oral cavities to the larynx ○​ Has three portions: nasopharynx, oropharynx, and laryngopharynx ​ Tonsils - made of lymphoid tissue at the junction of the oral cavity and pharynx ○​ Provide defense against inhaled pathogens ​ The larynx - cartilaginous structure between the pharynx and the trachea ​ The Adam’s apple (laryngeal prominence) is located at the front of the neck The larynx ​ Houses the vocal cords - mucosal folds supported by elastic ligaments ○​ The slit between the vocal cords is called the glottis ○​ When air passes through the glottis, the vocal cords vibrate, producing sound ○​ The greater the tension in the vocal cords, the higher the pitch ○​ When the glottis is wider, the pitch is lower ○​ Loudness depends on the degree to which the vocal cords vibrate  ​ When food is swallowed, the larynx moves upward against the epiglottis - a flap of tissue that prevents food from passing into the larynx Lower respiratory tract ​ The trachea ​ The bronchial tree ​ The lungs The trachea ​ Commonly called the “windpipe” ​ Connects the larynx to the primary bronchi ​ Its walls are reinforced by C-shaped cartilaginous rings, which prevent the trachea from collapsing ○​ The C shape allows the esophagus to expand when swallowing ​ Lined with pseudostratified ciliated columnar epithelium and goblet cells ○​ The goblet cells produce mucus, which traps debris from the air as it passes through the trachea ○​ The mucus is then swept away from the lungs and toward the pharynx by the cilia ​ Smoking damages the cilia, causing smoker’s cough ​ Tracheostomy - a breathing tube inserted into the trachea The bronchial tree ​ Two primary bronchi (sing., bronchus) lead from the trachea into the lungs ​ The primary bronchi branch into secondary bronchi, which continue to branch until they are small bronchioles about 1 mm in diameter ​ Bronchi have cartilage like the trachea, but as they get smaller, the cartilage disappears ​ During an asthma attack, the smooth muscle of the bronchioles contracts, constricting it and causing wheezing ​ Each bronchiole leads to an elongated space enclosed by many air sacs called alveoli (sing., alveolus) The lungs ​ Made up of the secondary bronchi, bronchioles, and alveoli ​ The right lung has three lobes while the left lung has two lobes (to make room for the heart) ​ Each lobe is divided into lobules ​ Each lung is enclosed by pleurae (sing., pleura) - two layers of serous membrane that produce serous fluid ​ The pleural fluid has surface tension, which adheres the parietal and visceral pleurae ○​ Surface tension is due to hydrogen bonds between water molecules  ○​ Because of surface tension, when the thoracic cavity enlarges, the parietal pleura “pulls” the visceral pleura, and therefore the lungs expands ​ This increases the size of the lungs ​ Pleurisy - inflammation of the pleurae; painful The alveoli ​ The lungs have about 300 million alveoli ​ Each alveolar sac is surrounded by blood capillaries ​ The walls of the sac and the capillaries are both made of simple squamous epithelium ​ Gas exchange occurs between air in the alveoli and blood in the capillaries Gas exchange Networks of airways and blood vessels Gas exchange in the body ​ Oxygen is needed to produce ATP, so must be supplied to all the cells, and the carbon dioxide produced must be removed from the body ​ Respiration includes the exchange of gases not only in the lungs but also in the tissues ​ The principles of diffusion govern whether O2 or CO2 enters or leaves the blood Gas exchange in the body ​ Gases exert pressure, and the amount of pressure each gas exerts is called its partial pressure, symbolized as PCO2 or PO2 ​ If the partial pressure of a gas differs across a membrane, it will diffuse from higher to lower partial pressure External respiration ​ Exchange of gases between the lung alveoli and the blood capillaries ​ PCO2 is higher in the lung capillaries than the air; thus, CO2 diffuses out of the blood into the lungs ​ The partial pressure pattern for O2 is just the opposite, so O2 diffuses from the alveolar air into the red blood cells in the pulmonary capillaries External respiration ​ Most of the CO2 is carried in plasma as bicarbonate ions (HCO3-) ​ In the low-PCO2 environment of the lungs, this reaction proceeds to the right: ​ Carbonic anhydrase - the enzyme that speeds the breakdown of carbonic acid (H2CO3) in red blood cells ​ Hyperventilation (breathing at a high rate) pushes the reaction to the right; blood has fewer hydrogen ions; alkalosis (high blood pH) occurs ​ Hypoventilation (breathing at a low rate) pushes the reaction to the left; acidosis (low blood pH) occurs ​ Hemoglobin carrying carbon dioxide - carbaminohemoglobin External respiration ​ Pulmonary capillary blood is low in oxygen, and alveolar air has a higher partial pressure of oxygen ​ Therefore, O2 diffuses into plasma and then into red blood cells in the lungs ​ Hemoglobin takes up oxygen and becomes oxyhemoglobin (HbO2) Internal respiration ​ Exchange of gases between the blood in systemic capillaries and the tissue cells  ​ Blood entering systemic capillaries is bright red because red blood cells contain oxyhemoglobin ​ After HbO2 gives up O2, it diffuses out of the blood into the tissues ​ Oxygen diffuses out of the blood into the tissues because the PO2 of interstitial fluid is lower than that of blood ○​ The lower PO2 is due to cells continuously using up oxygen during cellular respiration ​ Carbon dioxide diffuses into the blood from the tissues because the PCO2 of interstitial fluid is higher than that of blood ○​ Carbon dioxide is produced during cellular respiration and collects in interstitial fluid The relationship between air pressure and volume ​ Ventilation is governed by Boyle’s Law ○​ At a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume ​ This relationship controls inhalation and exhalation Mechanism of breathing ​ Ventilation (breathing), has two phases: ○​ Inspiration (inhalation) moves air into the lungs ○​ Expiration (exhalation) moves air out of the lungs ​ To understand ventilation, it is necessary to remember the following facts: ○​ Normally there is a continuous column of air from the pharynx to the alveoli of the lungs ○​ The lungs lie within the sealed thoracic cavity ○​ Rib cage - top and sides of the thoracic cavity ○​ Intercostal muscles - between the ribs ○​ Diaphragm - floor of the thoracic cavity ○​ The lungs adhere to the thoracic wall by way of the pleura ​ Space between the two pleurae is minimal and filled with pleural fluid Inspiration ​ The active phase of ventilation ​ The diaphragm and the external intercostal muscles contract ​ In its relaxed state, the diaphragm is dome-shaped; during inspiration, it contracts and becomes flattened ​ Contraction of the external intercostal muscles causes the rib cage to move upward and outward ​ Both actions increase the size of the thoracic cage  ​ As the thoracic volume increases, the lungs increase in volume as well, because the lung adheres to the wall of the thoracic cavity ​ As the lung volume increases, the air pressure in the alveoli decreases ​ Alveolar pressure is now less than atmospheric pressure, so air flows from outside the body into the lungs ​ Both actions increase the size of the thoracic cage ​ As the thoracic volume increases, the lungs increase in volume as well, because the lung adheres to the wall of the thoracic cavity ​ As the lung volume increases, the air pressure in the alveoli decreases ​ Alveolar pressure is now less than atmospheric pressure, so air flows from outside the body into the lungs Expiration ​ The passive phase of breathing; the diaphragm and external intercostal muscles relax ​ The rib cage returns to its resting position, moving down and inward ​ The lungs recoil, and the air pressure inside increases; air flows out ​ Surfactant keeps the alveoli from collapsing during expiration ​ Also, as the lungs recoil, the pressure between the pleurae decreases, and this keeps the alveoli open ○​ When, in an accident, the thoracic cavity is punctured (a “punctured lung”), air enters the space between the two pleurae, causing the lung to collapse Measuring the air capacity of the lungs Volumes of air exchanged during ventilation ​ Tidal volume - the amount of air that moves in and out with each normal breath ​ Vital capacity - the maximum volume that can be moved in plus the maximum amount that can be moved out during one breath ○​ The sum of tidal, inspiratory reserve, and expiratory reserve volumes ​ Inspiratory and expiratory reserve volume - the increased volume of air moving in or out of the body with forced inspiration and expiration ​ Some inhaled air never reaches the lungs; it fills the nasal cavities, trachea, bronchi, and bronchioles ○​ These passages are not used for gas exchange; they contain dead air space ​ Residual volume - the air remaining in the lungs after exhalation Control of ventilation ​ 1. Nervous control of breathing ○​ Respiratory control center in the brain automatically sends out nerve signals to the diaphragm and the external intercostal muscles of the rib cage, causing inspiration to occur ​ When the respiratory center stops sending nerve signals to the diaphragm and the rib cage, the muscles relax, and expiration occurs ○​ Although the respiratory center automatically controls the rate and depth of breathing, it is influenced by the nervous system ​ Can voluntarily change our breathing pattern for speaking, singing, eating, swimming underwater ​ Following forced inspiration, stretch receptors in the airway walls initiate inhibitory nerve impulses that stop the respiratory center from sending out nerve signals and overstretching the lungs 2. Chemical control of breathing ​ Cells produce CO2 during cellular respiration ​ CO2 then enters the blood, where it combines with water, forming an acid that breaks down and gives off hydrogen ions ○​ These H+ decrease the pH of the blood ​ Chemoreceptors - sensory receptors that are sensitive to the chemical composition of body fluids ​ Two sets of chemoreceptors sensitive to pH can cause breathing to speed up ○​ One set is in the medulla oblongata of the brain stem ○​ The other set is the carotid bodies of the carotid arteries, and aortic bodies of the aorta ○​ These chemoreceptors mostly respond to carbon dioxide levels of the blood  ​ When blood pH decreases, the respiratory center increases the rate and depth of breathing to remove CO2 from the blood ​ This increases the pH, so the breathing rate returns to normal ​ When you hold your breath, CO2 begins accumulating in the blood, decreasing the pH ​ The respiratory center, stimulated by the chemoreceptors, is able to override a voluntary inhibition of respiration, forcing breathing The Urinary System involves in maintaining the fluid balance Organs of the Urinary System ​ The urinary system consists of the ​ Kidneys (retroperitoneal) ​ Ureters (retroperitoneal) ​ Urinary bladder ​ Urethra Kidneys ​ One on each side of the vertebral column; partially protected by the rib cage ​ Due to the liver, the right kidney is positioned slightly lower than the left ​ Bean-shaped and reddish to brown in color ​ Covered by the renal capsule ○​ Fibrous connective tissue ​ Kidneys are retroperitoneal: lie behind the peritoneum Kidney structure: Gross anatomy ​ The three regions of a kidney ○​ Renal cortex - outer layer that dips down in between the inner layer called the renal medulla ○​ Renal medulla - consists of cone-shaped tissue masses called renal pyramids ○​ Renal pelvis - a central space that is continuous with the ureter Kidneys: Blood supply ​ The concave side of the kidney (renal hilum) is where a renal artery enters and a renal vein and ureter exit ○​ A branch from the aorta forms the renal artery ○​ The renal artery transports blood to the kidneys ○​ The renal vein carries filtered blood away from the kidneys ○​ The renal vein empties into the inferior vena cava Kidney structure: Microscopic features ​ Kidneys are composed of over 1 million nephrons ​ The nephrons filter the blood and produce urine ○​ Structural and functional unit of the urinary system ​ Several nephrons empty urine into one collecting duct ​ The collecting ducts empty into the renal pelvis ​ Two kinds of nephrons (refer to the diagram) ○​ 1. Cortical nephrons: the glomerulus is closer to the outer part of the cortex ○​ 2. Juxtamedullary nephrons: the glomerulus is closer to the cortex-medulla junction, the loop of Henle penetrates deep into the medulla ​ The glomerular capsule and the convoluted tubules always lie within the renal cortex ​ The loop of the nephron dips down into the renal medulla ​ Collecting ducts are also located in the renal medulla, and together they give the renal pyramids their striped appearance Structure of the nephron ​ Bowman’s capsule ○​ Receives filtered substances ​ Proximal convoluted tubule ​ Loop of Henle ​ Distal convoluted tubule ○​ Empties into collecting duct ​ Collecting duct Blood supply of the nephron ​ From the renal artery, an afferent arteriole transports blood to the glomerulus, a knot of capillaries inside the glomerular capsule ​ The efferent arteriole carries blood away from the glomerulus ​ Blood pressure is higher in the glomerulus than anywhere else in the body because the efferent arteriole is narrower than the afferent arteriole ○​ Important for the glomerular filtration (next lecture) ​ The efferent arteriole empties into the peritubular capillary network, which surrounds the rest of the nephron ​ Then the blood goes into a venule that carries blood into the renal vein (follow arrows when you study) Anatomy of a nephron ​ Glomerular capsule ○​ The outer layer is made of squamous epithelial cells ○​ The inner layer is made of podocytes that cover the glomerulus, leaving pores that allow molecules from the blood inside the glomerulus out into the glomerular capsule ​ Proximal convoluted tubule ○​ Its cuboidal epithelial cells have numerous microvilli that form a brush border; these increase surface area ​ Loop of the nephron (loop of Henle) ○​ Has a descending limb and an ascending limb; each has different permeabilities to water and solutes ​ Distal convoluted tubule ○​ Primary function is ion exchange between the blood and the renal tubule ○​ The distal convoluted tubules of several nephrons enter one collecting duct, which carries urine to the renal pelvis Ureters ​ Conduct urine from the kidneys to the bladder ​ The wall has three layers: an inner mucosa, a smooth muscle layer, and an outer fibrous coat of connective tissue ​ Peristaltic contractions in the ureter push urine into the bladder even when lying down Urinary bladder ​ Stores urine ​ Has three openings: two for the ureters, and one for the urethra, which drains the bladder ​ Folds in the mucosa called rugae disappear as the bladder enlarges ​ A layer of transitional epithelium enables the bladder to stretch (note the thickness of the epithelium) ​ Small folds of bladder mucosa act as a valve to prevent backward flow of urine into the ureter ​ There are two sphincters where the urethra exits the bladder ○​ The internal sphincter is composed of smooth muscle and is involuntarily controlled ○​ The external sphincter is composed of skeletal muscle that can be voluntarily controlled Urethra ​ Extends from the urinary bladder to an external opening ​ The short length of the female urethra makes women more susceptible to infections ​ In males, as the urethra leaves the male urinary bladder, it is encircled by the prostate gland ○​ The prostate sometimes enlarges, restricting the flow of urine in the urethra ​ In females, the reproductive and urinary systems are not connected ​ In males, however, the urethra carries urine during urination and sperm during ejaculation Urination (micturition) ​ When the urinary bladder fills with urine, stretch receptors are activated ​ These receptors send sensory nerve signals to the spinal cord ○​ Subsequently, motor nerve impulses from the spinal cord cause the urinary bladder to contract and the sphincters to relax, so that urination is possible ○​ The brain has control over micturition, too, by controlling the external urethral sphincter The urinary system ​ Carries out excretion - removal of metabolic wastes from the body ○​ Metabolic wastes are by - products of the cells and tissues’ normal activities ○​ Excretion is performed by the formation and discharge of urine from the body ​ Plays a major role in maintaining the salt, water, and pH homeostasis of the blood Excretion of metabolic wastes ​ Most are nitrogenous, such as urea, creatinine, ammonium, and uric acid ​ Urea - a waste product of amino acid metabolism ○​ The main nitrogenous waste of metabolism ○​ The breakdown of amino acids in the liver releases ammonia, which is very toxic ○​ The liver combines ammonia with CO2 to produce urea, which is much less harmful ○​ Uremia - elevated levels of urea in the blood ​ Can cause cardiac arrhythmia, vomiting, respiratory problems, and potentially death Excretion of metabolic wastes ​ The kidneys secrete creatinine and uric acid ​ Creatinine - results from the breakdown of creatine phosphate, an energy storage molecule in muscles ​ Uric acid - from the metabolic processing of nucleotides ○​ Insoluble; crystals form if too much is present in the blood ○​ Gout - collection of uric acid crystals in the joints Maintenance of water-salt balance ​ A principal function of the kidneys ​ Salts, such as NaCl, have the ability to influence the rate and direction of osmosis ○​ Therefore, the more salts there are in the blood, the greater the blood volume and the greater the blood pressure ​ By regulating the concentration of sodium (Na+) and potassium (K+) in the blood, the kidneys regulate blood pressure ​ The kidneys also maintain the appropriate levels of other ions such as bicarbonate (HCO3-) and calcium (Ca2+) Maintenance of acid-base balance ​ A healthy blood pH is about 7.4 ​ The kidneys monitor and help control pH by excreting H+ and reabsorbing HCO3- as needed ​ Urine usually has a pH of 6 or lower because the diet contains acidic foods Secretion of enzymes and hormones ​ The kidneys release renin, an enzyme that leads to aldosterone secretion ​ Aldosterone is a hormone produced by the adrenal glands, which lie atop the kidneys ​ Regulates the water-salt balance of the blood ​ The kidneys also release erythropoietin (EPO), a hormone that stimulates the production of red blood cells ​ Additional functions of the kidneys ○​ The kidneys also reabsorb filtered nutrients and participate in the synthesis of vitamin D ○​ Vitamin D is a hormone that promotes calcium ion (Ca2+) absorption from the digestive tract Urine formation ​ The formation of urine involves three stages: ○​ Glomerular filtration ○​ Tubular reabsorption ○​ Tubular secretion Glomerular filtration ​ Occurs when blood enters the glomerulus via the afferent arteriole ​ The afferent arteriole has a larger diameter than the efferent arteriole, resulting in an increase in glomerular blood pressure ​ This increased blood pressure forces more fluid and molecules to leave the glomerulus than in typical capillaries ○​ This fluid, called glomerular filtrate, enters the glomerular capsule ​ This process is called filtration because large molecules and formed elements are unable to pass through the capillary wall ○​ In effect, then, blood in the glomerulus has two portions: the filterable components and the nonfilterable components ​ Filterable blood components: ○​ Water, nitrogenous wastes, nutrients, salts (ions) ​ Nonfilterable blood components: ○​ Formed elements (blood cells and platelets), plasma proteins ​ The nonfilterable components leave the glomerulus by way of the efferent arteriole ​ Filtrate has the same concentration of filterable components as plasma Tubular reabsorption ​ Molecules are passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network ​ Na+ is actively transported by one of two ways: ○​ Symport - coupled to the movement of larger solutes, such as amino acids or glucose ○​ Antiport - moves Na+ into the cell while transporting out of the cell H+ ​ This also regulates the pH because the movement of H+ ions outward reduces the acidity of the blood ​ As Na+ is being moved, Cl- follows passively ​ The reabsorption of salt (NaCl) increases the osmolarity of the blood compared with the filtrate ○​ Therefore, water moves passively from the tubule into the blood ​ About 65% of Na+ is reabsorbed at the proximal convoluted tubule ​ Nutrients such as glucose and amino acids are reabsorbed at the proximal convoluted tubule ○​ Glucose is normally reabsorbed completely; there is a plentiful supply of carrier proteins Tubular secretion ​ The second way by which substances move from blood to the tubular fluid (the first is filtration) ​ H+, creatinine, and drugs such as penicillin are secreted  ​ Occurs along the length of the kidney tubule ​ In the end, urine contains: ​ Substances that have been filtered, but not reabsorbed, plus what has been secreted Homework ​ Label the diagram. ​ Label the diagram and show what happens in each step of urine formation.