Human Anatomy and Physiology: Blood Vessels, Respiratory, Digestive, and Urinary Systems
Blood Vessels
Types and Functions
- Coronary Artery: Carries oxygenated blood from the aorta to the heart muscle.
- Cardiac Vein: Carries deoxygenated blood from the heart muscle to the superior vena cava.
- Mesenteric Arteries: Carry oxygenated blood from the aorta to the intestines.
- Hepatic Portal Vein: Carries deoxygenated blood (full of nutrients) from the intestines to the liver.
- Hepatic Vein: Carries deoxygenated blood from the liver to the inferior vena cava.
- Renal Artery: Carries oxygenated blood from the aorta to the kidneys.
- Renal Vein: Carries deoxygenated blood from the kidneys to the inferior vena cava.
- Iliac Artery: Carries oxygenated blood from the aorta to the lower body.
- Iliac Vein: Carries deoxygenated blood from the lower body to the inferior vena cava.
- Arteries: Carry blood away from the heart to other organs.
- Arterioles: Receive blood from arteries; very small arteries that carry blood to capillaries.
- Capillaries: Sites of exchange of substances between blood and body cells.
- Venules: Receive blood from capillaries.
- Veins: Carry blood toward the ventricle of the heart.
Heart Valves and Sounds
Question 1: Structural Differences Between AV and Semilunar Valves
Answer: The AV valves have chordae tendinae attached to them and separate the atria from the ventricles, while the semilunar valves are located between the ventricles and the aorta/pulmonary artery.
Question 2: Blood Vessels Supplying Blood to the Heart
Answer: Coronary arteries
Question 3: Pathways of Systemic and Pulmonary Circuits
Answer:
- Pulmonary Circuit: Right atrium -> Right ventricle -> Pulmonary arteries -> Capillaries in lungs -> Pulmonary veins -> Left atrium -> Left ventricle
- Systemic Circuit: Superior and inferior vena cava -> Right atrium -> Tricuspid valve -> Right ventricle -> Pulmonary semilunar valve -> Pulmonary trunk -> Right and left pulmonary arteries -> Lungs/pulmonary capillaries (gas exchange) -> Right and left pulmonary veins -> Left atrium -> Bicuspid/mitral valve -> Left ventricle -> Aortic semilunar valve -> Aorta -> Branching arteries -> Arterioles -> Capillary beds (gas exchange in the body) -> Venules -> Veins -> Superior and inferior vena cava. Note: The right ventricle has deoxygenated blood, and the left atrium has oxygen-rich blood.
Question 4: Causes of Heart Sounds and Heart Murmur
Answer:
- The closing of heart valves causes the heart sounds “lub” and “dub”.
- The first sound (“lub”) occurs as the AV valves close.
- The second sound (“dub”) occurs when the semilunar valves close.
- A heart murmur is an abnormal heart sound, most often indicative of valve problems.
Intrinsic Conduction System of the Heart
The intrinsic conduction system follows this pathway: SA Node -> AV node -> AV bundle -> Bundle of His -> Purkinje fibers.
Question 5: Pacemaker of the Heart and Its Significance
Answer: The sinoatrial (SA) node is the pacemaker of the heart. It is specialized nervous tissue in the right atrium that initiates the heartbeat.
Question 6: Extrinsic Factors Affecting Heart Rate and Nervous System Control
Answer:
- Extrinsic factors affecting heart rate include hormonal responses, nervous system commands, environmental stress, and fitness.
- The cardiac control center is located in the ventrolateral medulla.
- Sympathetic stimulation increases the rate and strength of contractions.
- Parasympathetic stimulation decreases the rate and strength of contractions.
Fetal Heart Structures
- Foramen Ovale: Located in the interatrial septum, it permits blood flow directly from the right atrium to the left atrium (fossa ovalis).
- Ductus Arteriosus: Shunts blood from the pulmonary trunk into the aorta to bypass the nonfunctioning lungs (ligamentum arteriosum).
Respiratory System
Functions of the Respiratory System
- Pulmonary Ventilation: The inhalation and exhalation of air, involving the exchange of air between the atmosphere and alveoli.
- External Respiration: Exchange of gases between the alveoli of the lungs and the blood in pulmonary capillaries across the respiratory membrane. During this process, pulmonary capillary blood gains O2 and loses CO2.
- Internal Respiration: Exchange of gases between blood in systemic capillaries and tissue cells. This process involves the delivery of O2 and removal of CO2.
Pathway of Air
Air travels through the following pathway: External naris -> Internal naris -> Nasal pharynx -> Oral pharynx -> Laryngopharynx -> Larynx -> Trachea -> Left primary bronchus -> Secondary bronchus -> Tertiary bronchus.
Upper and Lower Respiratory Tracts
- Upper Respiratory Tract: Nose, nasal cavity (air enters the body), mouth, throat (pharynx), and larynx (voice box).
- Lower Respiratory Tract: Trachea, bronchi (branches from the trachea that are passageways of air to bronchioles), bronchioles (bring air into the lungs), and alveoli (allow gas exchange between O2 and CO2).
Question 7: Structure for Gas Exchange in the Lungs
Answer: Alveoli
Question 8: Serous Membrane Surrounding the Lungs and Its Layers
Answer:
- The serous membrane surrounding the lungs is called the pleura.
- Parietal Pleura: Forms the outer layer of the membrane.
- Visceral Pleura: Forms the inner layer of the membrane, covering the outside surface of the lungs.
Question 9: Central Nervous System Control of Breathing and Factors Affecting Rate and Depth
Answer: The central nervous system controls breathing through the medullary inspiratory center, pneumotaxic area, and apneustic area. Factors affecting the rate and depth of breathing include the chemistry of cerebrospinal fluid, blood chemistry, and stretch receptors in the lungs.
Digestive System
Pathway of Food
Food travels through the following pathway: Mouth -> Pharynx -> Esophagus -> Stomach -> Duodenum -> Jejunum -> Ileum -> Ascending colon -> Transverse colon -> Descending colon -> Sigmoid colon -> Rectum -> Anus.
Functions of the Digestive System and Its Structures
- Ingestion: Takes place in the mouth.
- Secretion: Salivary glands secrete saliva, the stomach secretes gastric juice, and the liver secretes bile.
- Mixing and Propulsion: Involves the movement of food through the digestive tract.
- Digestion: Includes mechanical digestion (physical breakdown of food) and chemical digestion (breakdown of food into simpler nutrients).
- Absorption: Primarily occurs in the small intestine.
- Defecation: Elimination of feces.
Mechanical and Chemical Digestion
- Mechanical Digestion: The physical breakdown of food into smaller pieces, starting in the mouth with chewing and continuing in the stomach with muscular contractions.
- Chemical Digestion: The breakdown of food into simpler nutrients through the action of enzymes, beginning in the mouth with saliva and continuing throughout the digestive tract.
Peristalsis
Peristalsis is the involuntary, wave-like contractions of the longitudinal and circular muscles that propel food through the digestive tract. It occurs in the esophagus, stomach, and intestines.
Layers of the Digestive Tract
- Outer Layer (Serosa): Areolar connective tissue.
- Muscularis: Circular muscle and longitudinal muscle.
- Submucosa: Dense irregular connective tissue.
- Mucosa: Simple columnar or stratified squamous epithelium.
Salivary Glands
- Parotid Gland: Located between the inferior surface of the zygomatic arch and the anterior margin of the sternocleidomastoid muscle. It is the largest salivary gland and produces saliva.
- Sublingual Gland: Located along either side of the lingual frenulum. It produces 10% of mucous.
- Submandibular Gland: Located on the floor of the mouth along the medial surfaces of the mandible. It produces 65% of mixed fluid (saliva).
Types of Teeth
- Canine: Located at the corners of the mouth, used for tearing food.
- Premolars: Located between the canines and molars, used for crushing and grinding food.
- Molars: Located at the back of the mouth, used for grinding food.
- Incisors: Located at the front of the mouth, used for biting and cutting food.
Pharynx
The pharynx is located in the throat and functions in swallowing. Muscular contractions of the oropharynx and laryngopharynx help propel food into the esophagus and then into the stomach.
Epiglottis
The epiglottis is a leaf-shaped flap of cartilage that covers the glottis (opening of the vocal cords) during swallowing, preventing food and liquid from entering the trachea.
Histological Layers of the GI Tract
- Mucosa: Contains the lamina propria (loose connective tissue) and muscularis mucosae.
- Submucosa: Consists of moderately dense irregular connective tissue and contains large blood vessels.
- Muscularis Externa: Typically smooth muscle tissue organized into circular and longitudinal layers. Contains the myenteric plexus.
- Serosa: Same as the visceral peritoneum. Contains mesothelium (simple squamous epithelium).
Stomach
The stomach functions in bulk storage of ingested matter, mechanical breakdown of resistant materials, and chemical digestion through the disruption of chemical bonds.
Microscopic View: The stomach wall contains gastric glands with secretory cells, including parietal cells (secrete intrinsic factor and hydrochloric acid), chief cells (secrete pepsinogen), and G cells (secrete gastrin).
Sphincters in the GI Tract
- Cardiac Sphincter: Located at the opening where the esophagus meets the stomach.
- Pyloric Sphincter: Located at the pylorus, connecting the stomach and small intestine.
- Anal Sphincter: Located at the anus.
Function: Sphincters regulate food movement and prevent backflow of undigested food.
Small Intestine
- Duodenum: 10 inches long (25 cm), connected to the pylorus of the stomach.
- Jejunum: 3 feet long (2.5 m), where most digestion occurs.
- Ileum: 6 feet long (3.5 m), the final segment of the small intestine.
Digestive Enzymes
- Pepsin: Produced by the stomach, breaks down proteins.
- Hydrochloric Acid: Produced by parietal cells in the stomach, converts pepsinogen to pepsin.
- Intrinsic Factor: Produced by parietal cells in the stomach, required for vitamin B12 absorption.
- Pepsinogen: Inactive form of pepsin.
Nutrients Absorbed in the Small Intestine
- Proteins
- Lipids
- Carbohydrates
Accessory Organs of Digestion
- Oral Cavity: Mechanical processing, moistening, mixing with salivary secretions.
- Salivary Glands: Secretion of lubricating fluid containing enzymes.
- Pharynx: Muscular propulsion of materials into the esophagus.
- Esophagus: Transport of materials to the stomach.
- Liver: Secretion of bile.
- Stomach: Chemical breakdown of materials via acid and enzymes, mechanical breakdown through muscular contractions.
- Gallbladder: Storage and concentration of bile.
- Pancreas: Exocrine cells secrete buffers and digestive enzymes.
- Small Intestine: Enzymatic digestion and absorption of water.
- Large Intestine: Dehydration and compaction of indigestible materials in preparation for elimination.
Pancreas: Exocrine and Endocrine Functions
- Exocrine Function: Produces enzymes important for digestion.
- Endocrine Function: Produces hormones, such as insulin and glucagon, that regulate blood sugar levels.
The exocrine function is responsible for the digestive contributions of the pancreas.
Insulin and Glucagon
Insulin and glucagon are produced in the pancreas. Insulin is secreted by beta cells and lowers blood sugar levels, while glucagon is secreted by alpha cells and raises blood sugar levels.
Diabetes Mellitus (DM)
Diabetes mellitus is a group of metabolic disorders characterized by high blood sugar levels over a prolonged period. The three main types are:
- Type 1 Diabetes: The body’s immune system attacks and destroys the insulin-producing cells in the pancreas. People with type 1 diabetes require lifelong insulin therapy.
- Type 2 Diabetes: The body becomes resistant to insulin or doesn’t produce enough insulin. It is often associated with lifestyle factors such as obesity and physical inactivity.
- Gestational Diabetes: Develops during pregnancy and usually resolves after delivery. However, it increases the risk of developing type 2 diabetes later in life.
Importance of Treatment: Untreated diabetes can lead to serious complications, including heart disease, stroke, kidney disease, nerve damage, and blindness.
Treatment: Treatment for diabetes depends on the type and severity. It may include lifestyle modifications, medications, and insulin therapy.
Bile Emulsification of Fat
Bile, produced by the liver, emulsifies fat by breaking it down into smaller droplets, increasing its surface area for digestion by lipase.
Large Intestine
The large intestine consists of the cecum, colon, and rectum. Its functions include reabsorption of water and electrolytes, compaction of intestinal contents into feces, absorption of vitamins produced by bacteria, and storage of fecal material before defecation.
Anal Sphincters
The internal and external anal sphincters are made up of smooth muscle.
Urinary System
Organs and Functions
- Kidneys: Produce urine.
- Ureters: Transport urine from the kidneys to the bladder.
- Urinary Bladder: Stores urine.
- Urethra: Eliminates urine from the body.
Kidney Location
The kidneys are located on either side of the vertebral column between the last thoracic and third lumbar vertebrae.
Kidney Structures
- Medulla: Contains the renal pyramids and renal papilla.
- Cortex: Contains the nephrons and blood vessels.
Vasculature Pathway of the Kidneys
Renal artery -> Segmental arteries -> Interlobar arteries -> Arcuate arteries -> Interlobular arteries -> Afferent arterioles -> Glomerular arterioles -> Efferent arterioles -> Peritubular capillaries -> Interlobular veins -> Arcuate veins -> Interlobar veins -> Renal vein.
Renal Corpuscle
The renal corpuscle consists of the glomerulus (a capillary network) and Bowman’s capsule. The outer layer of Bowman’s capsule is lined by simple squamous parietal epithelium, while the visceral epithelium consists of podocytes that wrap around the glomerular capillaries.
Urine Formation
- Glomerular Filtration: Blood plasma is filtered through the glomerulus into Bowman’s capsule.
- Tubular Reabsorption: Substances needed by the body are reabsorbed from the filtrate back into the blood.
- Tubular Secretion: Waste products and excess substances are secreted from the blood into the filtrate.
Collecting Ducts
The collecting ducts gather the remaining filtrate and regulate electrolytes, ultimately producing urine.
Microscopic Layers of Ureters and Urinary Bladder
- Ureters: Inner mucosa (transitional epithelium), middle muscular layer (longitudinal and circular smooth muscle), outer connective tissue layer.
- Urinary Bladder: Mucosa (transitional epithelium), submucosa, muscularis layer (inner and outer longitudinal layers with a circular layer in between), serosa (covers the superior surface).
Disorders of the Urinary System
Age-related changes in the urinary system include a declining number of functional nephrons, reduced glomerular filtration, reduced sensitivity to ADH, and problems with the micturition reflex.