Block Theory 3 Flashcards
Explain the respiratory system.
The respiratory system facilitates breathing and allows the body to acquire oxygen, which is required for metabolic function and cell survival. This system is made up of many organs that contribute to the conduction of air to and from the lungs, as well as gas exchange within the lungs.
What are the cyclic phases of breathing?
- Inspiration: draws oxygen rich air into the lungs.
- Expiration: forces oxygen poor air out of the lungs.
What are the functions of the respiratory system?
The respiratory system not only provides the structures for mechanical breathing, but also contributes to the functional mechanisms of respiration and immunity.
Gas exchange: involves the movement of gases across membranes. External respiration is the exchange of gas between the air and blood, where inspired oxygen moves across the cellular membranes of the alveolus of the lung and its associated capillaries into the blood, while carbon dioxide, moves in the opposite direction and out of the body through expiration. Internal respiration is a similar, exchanging gases between the blood and cells of the body.
Gas conditioning: gases entering the lungs need to be warmed and cleansed to prevent damage to the lungs. The conditioning of gases occurs in the nasal cavities and paranasal sinuses where air is swirled around to become warmed and humidified. Inhaled air is cleansed of particulate matter, through contact with the mucosal lining of respiratory epithelium.
Sound production: singing or speech, occurs by forceful expiration of air through the vocal cords in the larynx, causing them to vibrate. Different tensions of the vocal cords produce different sounds with help from the teeth, lips, and tongue.
Olfaction: olfactory epithelium covers the top of the nasal cavity with receptors for the sense of smell located within. When air is inhaled, airborne molecules dissolve in the mucus which lines the cavity and stimulates the receptors. Signals from these receptors travel to the brain through the olfactory nerve resulting in a sense of smell.
Defense: many airborne molecules and microbes can cause disease. The respiratory system has a line of defence against these molecules that cause infection. Course hairs of the nostrils, the ciliated cells of the respiratory epithelium, and the mucus lining help to trap particles and microorganisms from entering the nose and respiratory system.
What chamber of the heart does the deoxygenated blood exit from to enter the lungs?
The right ventricle
What chamber of the heart does oxygenated blood re-enter after exiting the lungs?
The left atrium
Discuss the respiratory tract epithelium.
RTE plays a large part in the defence of this system and lines most of the surfaces from the nasal cavity down to the terminal bronchi.
Pseudostratified ciliated columnar epithelium: the epithelium of the respiratory tract is pseudostratified, meaning that all cells are attached to the basal lamina, but only some reach the surface. The apical surface of the epithelium is covered in cilia, which are small finger like projections extending from the cell to increase surface area for conditioning air. These cilia also function to trap particles and microorganisms caught in mucus, and sweep them out of the respiratory tract.
Goblet mucus cells: found interspersed throughout the pseudostratified epithelium to produce mucus that forms a protective layer over the epithelium and traps particulate matter that may be inhaled. It also provides moisture to humidify the air.
What are the regions of the respiratory system?
Conducting portion: functions to transfer inhaled air from the outside world to the lung tissue, also conducting air from the lungs to the outside world. This is where humidification and trapping of debris occurs. No oxygen is absorbed into the blood in this region as the walls of the organs are too thick.
Respiratory portion: functions to transfer gases between the lungs and pulmonary capillaries. The pulmonary capillaries are the terminal structures within the lungs that have walls thin enough to facilitate the movement of gases from air to blood and vice versa.
Discuss the paranasal sinuses.
Paranasal sinuses are collection of air filled spaces within the bones of the skull communicating with the nasal cavity. The sinuses aid in the conditioning of air, defense, and act as resonance chambers for speech.
Paranasal sinuses are named after the bones of the skull that contain them. These include the frontal sinus, maxillary sinus, ethmoid sinus, and sphenoid sinus.
Paranasal sinuses are lined with respiratory tract epithelium for defence and conditioning.
Discuss the nasal cavity.
The nasal cavity is the first line of defence against invading pathogens, trapping them in coarse hairs and mucus. Air enters the vestibules of the nostrils and is passed into the nasal cavity where it is conditioned.
What are the nasal cavity boundaries?
The nasal cavity is surrounded by boney structures that create the 6 boundaries of the cavity.
Roof: the ethmoid bone
Floor: the hard palate
Medial wall: the nasal septum, composed of the vertical bones in the skull, separating the two halves of the nasal cavity
Lateral wall: contain structures known as nasal conchae that create turbulence in the air for conditioning and catching debris
Anterior: made of nares, the opening between the nose and nasal cavity
Posterior: opening to the nasopharynx (choanae), where the nasal cavity connects to the pharynx
Discuss the nasal cavity Histology.
The nasal cavity is mostly covered in RTE because if it’s role in protection and the conditioning of air. However, the roof of the nasal cavity is lined with olfactory epithelium which contains sensory receptors for smell. Olfactory epithelium is composed of pseudostratified ciliated columnar epithelium and bipolar olfactory receptor neurons.
Discuss the pharynx
The pharynx is a muscular tube that connects the nasal cavity in the larynx in the respiratory system. It also connects the oral cavity with the esophagus in the digestive system.
Nasopharynx: superior aspect of the pharynx
Oropharynx: middle aspect of the pharynx, acting as part of both the respiratory and digestive systems, passing air from the nasopharynx and food from the oral cavity into the laryngopharynx
Laryngopharynx: inferior aspect of the pharynx involved in both the digestive and respiratory systems, passing food and air into the respective systems
What is a Histology of the pharynx?
The nasopharynx is mostly RTE, because of its main respiratory function, while the oropharynx and laryngopharynx are lined with stratified squamous epithelium for durability when swallowing food.
When on an airplane, what is a good solution to equalize pressure in the middle ear?
A good solution is to swallow forcefully. The part of the pharynx that is associated with this is the nasopharynx.
Discuss the larynx
The larynx is the organ that produces sound, it is also known as the voicebox. It is made up of cartilage, ligaments, and associated muscles to serve its purpose. The larynx sits anterior to the esophagus, connecting the pharynx with the trachea and preventing food from entering the trachea.
What are the cartilages that make up the larynx?
Many cartilages serve to protect, attach, and aid in the function of the vocal cords.
Epiglottis: spoon shaped elastic cartilage that prevents food from passing into the trachea. During swallowing, the epiglottis flips downwards, and covers the opening of the trachea.
Thyroid cartilage: shield shaped hyaline cartilage that provides attachment for muscles as well as the vocal cords.
Cricoid cartilage: complete ring of hyaline cartilage that is narrow anteriorly and broad posteriorly, functioning as an attachment for muscles and vocal cords.
What are vocal cords?
Vocal cords are small ligaments attach to the laryngeal cartilages that vibrate when air is forced out of the lungs. When they vibrate, sound is produced. Different sounds can be made by altering the tension on the cords. True vocal cords are protected by a membranous flap, called the false vocal cords.
Discuss the trachea
The trachea extends from the larynx to the level of T4/T5 where it splits at the carina. The function of the trachea is the conduction of air to the lungs. The trachea is made up of 15 to 20 C-shaped cartilaginous rings which are incomplete posteriorly and function to keep the airway open. These rings are connected posteriorly by the trachealis muscle.
What is the Histology of the trachea?
Mucosa: RTE to clear debris that make it into the lower respiratory tract
Submucosa: made up of loose connective tissue containing larger vessels and nerves, as well as mucus, secreting glands.
Adventitia: outer layer of connective tissue surrounding the trachea and enclosing the C-shaped cartilaginous rings made of hyaline cartilage. These rings make the trachea flexible and durable for when organs in the thoracic cavity shift with breathing.
What type of cartilage are the cartilaginous rings of the trachea?
Hyaline
What are primary bronchi?
The left and right primary bronchi have the same functional and histological features as the trachea. Each primary bronchus enters its respective lung on the medial side at the hilus. The right primary bronchus is wider, shorter, and more vertical than the left primary bronchus.
Discuss the end of the conducting portion
The end of the conducting portion is characterized by bronchi dividing into smaller and smaller tubes. They move from a larger diameter, thick walled tube to a smaller diameter, thin walled tube for gas exchange. There’s also a corresponding change in histology as you move down the tree.
What is the order in which air travels from the environment to the end of the conducting portion of the respiratory system?
Nasal cavity, pharynx, larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, terminal bronchioles.
What is the respiratory portion?
The respiratory portion serves to allow for gas exchange between air and blood. It is important to cells in the body need to absorb oxygen and expel carbon dioxide to survive. At this level of the bronchial tree, the walls of the remaining structures are one cell layer thick and gases are able to cross the membrane easily.
Discuss the lungs
The respiratory portion makes up a majority of the lung tissue within both lungs. The lungs are located on either side of the heart within the thoracic cavity. The right lung is larger than left, due to the positioning of the heart.
Right lung: has three lobes (superior, middle, inferior) and two fissures (horizontal, oblique)
Left lung: has two lobes (superior, inferior), a cardiac notch, the lingula which covers the heart from the superior lobe, and one fissure (oblique)
What are the surfaces of the lungs?
Apex: superior point of the lungs sitting above the first rib
Diaphragmatic: base of the lung that rests on the diaphragm
Costal: named after the adjacent ribs, curving around the lateral aspect of the lung
Mediastinoscopy: the medial surface that contains the entry and exit points for all vessels and airways at the hilus
What are pleural membranes?
The pleura consists of two continuous membranes that form a sac around each lung. The pleura secretes pleural fluid to fill the pleural space between those two membranes. This fluid acts as a lubricant, allowing the visceral pleura to slide freely on the parietal pleura during inflation and deflation.
Parietal pleura: outer serous membrane attached to the walls and floor of the thoracic cavity around the lungs, being continuous with the visceral pleura at the hilus of the lung where it reflects inwards.
Visceral pleura: a serous membrane attached to the surface of the lung that is continuous with the parietal pleura at the hilus.
What are the structures of the respiratory portion?
Respiratory bronchioles: branch from the terminal bronchioles and are the first structures to contribute to gas exchange in the lungs. These are thin walled ducts with simple ciliated cuboidal epithelium that continue to branch into alveoli.
Alveoli: the functional unit of the lung where gas exchange takes place. Each alveolus is surrounded by capillaries to maximize the amount of oxygen going into the body and carbon dioxide leaving the body.
What is the digestive system?
The digestive system is a multi organ system of the body divided into two groups. The digestive tract is a continuous tube that starts in the oral cavity and ends inferiorly with the anal canal. Each organ plays an integral role in the breakdown of food and uptake of nutrients.
Alimentary canal: mouth, oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
Accessory digestive organs: tongue, teeth, salivary, glands, liver, biliary ducts, gallbladder, and pancreas.
What are the functions of the digestive tract?
Digestion: mastication crashes food in the mouth into smaller pieces to facilitate chemical processing by enzymes into small molecules.
Absorption: digestion is completed in the small intestine, where most nutrients are absorbed. In the large intestine, water and vitamins are absorbed.
Secretion: in the presence of food, cells of the stomach’s mucosal wall release gastric acid to perform chemical digestion.
Motility: muscles of the esophageal wall contract and relax to push food through the esophagus down to the stomach.
Elimination of waste: leftover materials that are not absorbed or utilized by the body are eliminated by the process of defecation.
What is the general histological organization of the digestive tract wall?
Mucosa: the innermost layer of the digestive tract wall composed of the surface epithelium (reflecting the organs function), the lamina propria (loose connective tissue), and the muscularis mucosa (smooth muscle fibres under the lamina propria).
Submucosa: below the mucosa, composed of dense irregular connective tissue containing blood vessels, lymphatics, glands, and nerve plexuses.
Muscularis Externa: composed of circular and longitudinal layers of smooth muscle with nerve plexuses for muscular contraction to propel food through the digestive tract.
Serosa/Adventitia: the outer most layer of the digestive tract. Serosa secretes lubricating fluid, while adventitia is just a layer of loose connective tissue.
What is the oral cavity?
The oral cavity is the first part of the digestive tract, consisting of two parts:
The vestibule: the space between the cheeks/lips and the gums/teeth
The oral cavity proper: includes the other areas of the mouth
What is the palate?
The palate makes up the superior border of the oral cavity. It is divided into the hard palate (bone) and
soft palate (muscle). The posterior extension of the soft palate is the uvula.
What is the tongue?
The tongue is a muscle associated with speech, taste, and the mechanical manipulation of food. It is made up of intrinsic muscle that control the shape of the tongue and extrinsic muscles that move the tongue during chewing and speech.
On the inferior surface of the tongue is the frenulum, which anchors the tongue to the floor of the
mouth.
What are papillae?
Papillae are bumps that cover the superior and lateral surfaces of the tongue are covered in papillae. There are four types of papillae, some of which contain taste buds, allowing humans the sense of gustation.
What are salivary glands?
Salivary glands secrete digestive enzymes and mucus to help break down food during mastication. There are three major glands with different secretions.
Parotid: secretes serous fluid
Submandibular: secretes serous and mucous (viscous) fluid
Sublingual: secretes mucus
Discuss teeth
Humans have two sets of teeth. The first are deciduous teeth, the second are permanent teeth. Teeth are important for the mechanical digestion of food.
Deciduous: consist of 2 incisors, 1 canine (cuspid), and 2 molars in each quadrant of the jaw. This totals to 20 teeth in the whole mouth.
Permanent: consists of 2 incisors, 1 canine (cuspid), 2 premolars (bicuspids), and 3 molars in each quadrant of the jaw. This totals 32 teeth in the whole mouth.
What are tonsils?
Tonsils are collections of lymphoid tissue in areas of the pharynx. They play a role in the
immune system.
There are three tonsils:
- Palatine tonsils
- Pharyngeal tonsil
- Lingual tonsils
Explain the gross anatomy of the esophagus
The esophagus is a muscular tube, measuring 25 cm in length and extending from the pharynx to the stomach.
Explain the histology of the esophagus
Mucosa: stratified squamous epithelium protects the esophagus from friction as food travels to the stomach.
Submucosa: contains mucus‑secreting glands, which help lubricate the passage of food.
Muscularis Externa: consists of both smooth and skeletal muscle.The upper 1/3 is only skeletal muscle, the middle 1/3 is mixed, and the lower 1/3 is smooth muscle.
Serosa/Adventitia: covered by adventitia.
Discuss the stomach
The stomach is a J-shaped organ divided into the fundus, body, and antrum which is continuous with the duodenum.
The shape of the stomach gives rise to the lesser and greater curvatures.
The greater omentum is a structure that hangs off of the greater curvature of the stomach to cover and protect abdominal viscera.
Explain the histology of the stomach
Mucosa: folded into rugae that
allow the stomach to expand. The epithelium is simple columnar and contains gastric glands that secrete acids for chemical digestion. Epithelium secretes mucus to protect the stomach from acids secreted by the gastric glands.
Submucosa: contains blood vessels, lymphatics, glands, and nerve plexuses, which supply the stomach tissue with oxygen and control contraction of the musculature.
Muscularis Externa: has three layers of smooth muscle: an outer longitudinal, middle circular, and inner oblique layer.
Serosa: the stomach is covered in serosa.
Discuss the intestines
Digested material travels from the stomach into the intestines, where is it further digested and excreted from the body. The intestines are composed of small intestines and large intestines.
Explain the gross anatomy of the small intestine
The small intestine is 6 metres long and is attached to the posterior abdominal wall.
Duodenum (25 cm): C-shaped and encloses the head of the pancreas.
Jejunum (2.5 m): lies in the left upper quadrant of the abdomen.
Ileum (3.5 m): lies in the right lower quadrant of the abdomen.
Explain the mucosa of the small intestine
Villi: fingerlike projections that extend into the lumen
of the small intestine.
Epithelium: found on the villi as simple columnar with many
absorptive cells whose apical surfaces have microvilli to increase the surface area of absorption.
Lamina Propria: forms the core of each villus, containing blood and lymphatic capillaries. Collections of lymphatic tissue, Peyer’s patches, are abundant in the ileum.
Intestinal Glands: deep folds
of mucosa between villi that secrete intestinal juices.
Pilcae Circulares: mucosa and submucosa form plicae circulares, permanent
transverse folds, that increase the surface area for absorption.
Explain the submucosa of the small intestine
The submucosa of the duodenum has duodenal (Brunner’s) glands that secrete alkaline mucus to protect the small intestine from stomach acid. These glands are only in the duodenum.
Explain the muscularis externa of the small intestine
The small intestine has two smooth muscle layers (circular and longitudinal). Between these layers is a nerve plexus.
Is the small intestine covered by serosa or adventitia?
Serosa
Explain the gross anatomy of the large intestine
The large intestine is the terminal portion of the digestive tract consisting of the cecum, colon, the rectum.
Cecum: first portion of the large intestine, with an extension off of it called the vermiform appendix.
Colon: the second portion of the large intestine, divided into four sections.
- Ascending Colon
-Transverse Colon
-Descending Colon
-Sigmoid Colon
Rectum: extends from the sigmoid colon to the anal canal. It temporarily stores fecal matter before defecation.
Explain the mucosa of the large intestine
The mucosa of the large intestine is similar to the small intestine, but does not contain plicae circulares or villi.
Epithelium: simple columnar with an increasing amount of goblet cells as you move
towards the anus. In the anal canal, a change from simple columnar to stratified squamous epithelium takes place.
Intestinal Glands: like in the small intestine, intestinal glands are also present in the large intestine. In addition,
accumulations of lymphatic tissue are present in the lamina propria and submucosa.
Explain the submucosa of the large intestine
The submucosa contains blood vessels, lymphatics, glands, and nerve plexuses.
Explain the muscularis externa of the large intestine
Depending on its location, the muscularis externa has a unique arrangement.
Cecum & Colon: the outer longitudinal layer forms three teniae coli that contract the wall of the large intestine, forming sac-like haustra.
Rectum: the three teniae coli merge to form the continuous longitudinal muscular layer.
Anal Canal: the circular muscle layer thickens into the internal anal sphincter.
Is the large intestine covered in serosa or adventitia?
The large intestine can be covered in either adventitia or serosa
Discuss the anal canal
The anal canal is the last portion of the digestive tract that leads into the external world.
Anal Column: longitudinal ridges in the canal.
Internal/External Anal Sphincters: help with the excretion of waste.
Explain the pathway of food
Oral Cavity, Esophagus, Stomach, Duodenum, Jejunum, Ileum, Cecum, Colon, Rectum, and Anal Canal
What are accessory organs for the digestive system?
The accessory organs are a significant part of acquiring nutrients from food. They provide enzymes for the breakdown of food molecules and bile for the digestion of dietary fat. This is an
important process in the storage of molecules that provide energy for the body.
Liver: produces bile for the digestion of fats and stores glucose in the form of glycogen, so that it can be later broken and used for energy. The liver also plays a role in the metabolism of toxins, drugs, and alcohol in the blood.
Gallbladder: functions in the storage and release of bile in
the digestive system.
Pancreas: mixed gland with endocrine functions that control levels of blood glucose, and exocrine functions that secrete digestive enzymes into the intestine.
Discuss the liver
The liver sits in the URQ, inferior to the diaphragm and anterior to the inferior vena cava (IVC). The liver has four lobes: right, left, caudate, quadrate.
Ligaments of the liver attach the liver to the surrounding abdominal peritoneum and the
diaphragm. The right and left lobes are separated by the falciform ligament. The coronary ligament suspends the liver from the inferior surface of the diaphragm
What is the porta hepatis?
The porta hepatis, or hilum, of the liver is where the hepatic vessels and ducts enter and
leave the liver.
What structures enter and exit the porta hepatis?
Common Hepatic Duct: drains bile produced in the liver, joining with the cystic duct of the gallbladder to form the common bile duct.
Portal Vein: carries nutrient rich blood from the digestive system to the liver, where nutrients can be stored or toxins can be metabolized.
Hepatic Artery: carries oxygenated blood to the liver and branches to supply each lobe.
Discuss the histology of the liver
The functional unit of the liver is the hexagonal-shaped liver lobule. Each lobule is made up of simple cuboidal hepatocytes, arranged in plates that radiate outward from a central vein. Between the plates are sinusoids where venous blood flows.
What are portal triads?
The portal triads are branches of the hepatic artery, portal vein, and common hepatic duct from the porta hepatis. Each lobule is surrounded by six triads, one at each corner of the hexagon.
How does blood flow through the liver?
Nutrient rich blood from the portal veins travels into the sinusoids to be taken up into hepatocytes. Then, the blood in the sinusoids drains into the central veins, which join to form the hepatic veins. Finally, blood from each hepatic vein drains to the inferior vena cava and eventually to the heart
portal veins - sinusoids - hepatocytes - sinusoids - central veins - hepatic veins - inferior vena cava - heart
how does bile flow through the liver?
Bile is produced by hepatocytes to aid in the digestion of dietary fats.
From the hepatocytes, bile drains into canaliculi channels that empty into the bile ductules of the portal triad, and eventually into the hepatic ducts. The hepatic ducts join to form the common hepatic duct.
Discuss the gallbladder
The gallbladder is a pear-shaped muscular sac that lies inferior to the right lobe of the liver. It stores and concentrate bile not immediately required for digestion.
Fundus: anterior
Body: between the fundus and the neck.
Neck: posterior - connected to the cystic duct.
What is the biliary system?
The biliary system consists of interconnected ducts that connect the liver and the gallbladder. This duct
system stores and drains bile into the duodenum.
Hepatic Ducts: right and left hepatic ducts from the right and left lobes of the liver drain bile into the common
hepatic duct.
Cystic Duct: attaches to the common hepatic duct and functions to transport bile to and from the gallbladder.
Common Bile Duct: meets the cystic duct to drain bile into the common bile duct, which
enters the duodenum.
What is the pancreas?
The pancreas is a lobular organ that lies deep to the stomach. It is a mixed gland with both 99% exocrine and 1% endocrine function.
The exocrine function of the pancreas involves the secretion of pancreatic juices from the pancreatic acini into the duodenum. Pancreatic juices are rich in digestive enzymes and contain bicarbonate ions to neutralize acid from the
stomach
The pancreas is divided into three sections: the head, body, and tail. The head of the pancreas sits at the duodenum, the tail abuts the spleen.
What is the main pancreatic duct?
The main pancreatic duct collects the exocrine products of the pancreas and fuses with the common bile duct to empty into the duodenum at the hepatopancreatic ampulla of Vater.
What are Kidneys?
The kidneys mark the beginning of the urinary system. They filter blood to produce urine which is excreted from the body through a series of tubes and organs to get rid of waste and excess ions.
The kidneys are a pair of bean-shaped organs located on either side of the T12-L2 vertebrae. They are roughly ‘fist-sized’ organs that lay against the posterior abdominal wall.
Their average size is:
* 12 cm in length
* 6.5 cm in width
* 2.5 cm in thickness
The right kidney sits slightly lower in the abdominal cavity than the left one. This is because of the liver’s location.
Discuss the kidney’s surface anatomy
Medially, the kidneys have a hilum where the renal arteries and nerves enter, and renal veins as well as the ureters exit. The hilum is continuous with the renal sinus, which is filled with fatty tissue.
Each kidney is surrounded by supportive tissue layers that protect and cushion the kidneys.
Renal Capsule: covers the outer surface of the kidney. It is composed of dense irregular connective tissue that protects the kidneys from injury
or pathogens and maintains the shape of the kidneys.
Adipose Capsule: perinephric fat, is a layer of adipose tissue external to the renal capsule. It
offers cushion and protection by completely surrounding the kidney.
Describe the internal anatomy of the kidneys
The kidney is divided into the cortex and medulla. These
regions filter blood to make urine.
Extensions of the cortex, called renal columns, separate the medulla into renal pyramids. The apex of each pyramid is termed the renal papilla. Based on this organization, the kidney is divided into renal lobes. Each lobe consists of a renal pyramid, its overlying cortex, and surrounding renal column.
Urine produced in the kidneys flows through the renal papilla into a funnel-shaped space termed the minor calyx. Each minor calyx drains into a major calyx, and then into the large renal pelvis, which continues on as the ureter.
How do the kidneys receive and drain blood?
Blood Supply: kidneys receive blood from paired renal arteries, branches of the abdominal aorta.
Blood Drainage: kidneys are drained by the renal veins, which are anterior to the arteries and drain into the inferior vena cava.
The right renal artery is longer than the left renal artery, whereas the right renal vein is shorter than the left renal vein. This is due to the positioning
of the IVC and descending aorta relative to one another.
Explain the kidney histology
The kidney is made up of millions of functional units, known as nephrons. These units filter the blood and produce urine. The nephron is composed of two parts: a renal corpuscle and a renal tubule.
Renal corpuscle: composed of a glomerulus and a glomerular capsule (Bowman’s capsule). The glomerulus: consists of a bundle of capillaries enclosed within the glomerular capsule which creates Bowman’s space between its walls and the glomerular capillaries. Blood flows into the kidney and to the glomerular capillaries. Filtration occurs when components of the blood move out from the capillary into Bowman’s space. The material in the Bowman’s space is filtrate. The capillaries of the glomerulus have fenestrations that allow ions, water, and other molecules to move through their membranes. The glomerular capillaries are also surrounded and supported by podocytes that wrap their foot-like processes around the
glomerular capillaries creating filtration slits that permit the passage of water and salts and restrict the passage of proteins.
Renal tubule: extends throughout the cortex and the medulla of the kidney. It is divided into three sections: the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. Each section has a specific function in the reabsorption or secretion of substances such as ions, proteins, and water to and from the filtrate.
What is the collecting system?
From the renal tubules, the filtrate travels into collecting tubules, and then to the collecting ducts that travel within the renal medulla. The final processing of the filtrate occurs in the collecting duct where it is further modified. Once the filtrate leaves the collecting duct at the renal papilla it can be called urine
What does the juxtaglomerular apparatus do?
The juxtaglomerular apparatus is a specialized structural unit that regulates the blood pressure of the body by monitoring ion concentrations in the filtrate
Juxtaglomerular Cells: smooth muscle cells of the afferent arteriole.
Macula Densa: cuboidal cells of the distal convoluted tubule.
What are the main functions of the kidneys?
The kidneys are the organs that filter the blood to rid the body of wastes, balance ion concentrations and body fluid volume, and produce erythropoietin. They produce urine via the nephrons, and pass the filtrate on to the minor and major calyces, and into the renal pelvis where it drains into the ureters.
What is the urinary tract?
The urinary tract transfers and stores the urine produced by the kidneys until it is ready for excretion. It consists of the ureters, bladder, and urethra.
Explain the ureters
The ureters are two long, thin, muscular tubes connecting the kidneys with the bladder. They begin as a continuation of the renal pelvis and extend towards the pelvic cavity where they penetrate the posterior wall of the bladder.
Histologically, the wall of the ureter is made up of three layers. The mucosa is lined with transitional epithelium, the muscularis consists of smooth muscle, and the ureters are lined with adventitia.
What is the bladder?
The urinary bladder is a muscular, expandable, sac-like pelvic organ that functions to temporarily store urine. The trigone overlies the base of the internal aspect of the bladder. It is enclosed by the two ureteric openings superiorly, and the internal urethral
opening inferiorly, and acts as a funnel that directs urine into the urethra. The trigone has a high density of afferent neurons that transmit the urge to void
The neck of the bladder is the constricted portion that is connected to the urethra inferiorly. It is surrounded by an internal urethral sphincter that is made up of smooth muscle and is under involuntary control.
What is the histology of the bladder?
The interior of the bladder has a folded appearance due to the presence of rugae that allow bladder expansion. This is in contrast to the trigone, which is smooth as it lacks rugae.
The mucosa is composed of transitional epithelium.
The muscularis is made up of three layers of muscle that are collectively called the detrusor muscle.
Where is the bladder located?
The bladder sits in the pelvic cavity posterior to the pubic bone. The spatial relationships of the bladder differ in males and females due to differences in pelvic structure and organs.
Female:
* Posterior to pubic symphysis
* Inferior to uterus
* Anterior to vagina
Male:
* Posterior to pubic symphysis
* Anterior to rectum
What is the urethra?
The urethra is a muscular tube connecting the neck of the bladder with the outside world at the external urethral meatus.
The epithelial lining of both the male and female urethrae starts out as transitional, gradually becoming stratified.
Unlike the female urethra which is 3-5 cm long, the male urethra is about 20 cm in length and is divided into three regions.
Prostatic Urethra: 3-4 cm passing through the prostate gland
Membranous Urethra: 2 cm from the prostate to the beginning of the penis. The voluntary external urethral sphincter surrounds this area.
Penile (Spongy) Urethra: 15 cm long through the penis
Explain the flow of urine
Glomerulus, Bowman’s Capsule, Proximal Convoluted Tubule, Loop of Henle, Distal Convoluted Tubule, Collecting Duct, Renal Papilla, Minor Calyx, Major Calyx, Renal Pelvis, Ureter, Bladder, Urethra, External Urethral Meatus
What is micturition?
Micturition is the act of urination. As the urinary bladder contracts, the external urinary sphincter relaxes to expel urine from the bladder into the urethra, and then outside the body.
What is incontinence?
The inability to voluntarily control the expulsion of urine. This leads to patients urinating accidentally and has to do with the external urethral sphincter and somatic motor nervous system.
Discuss the male reproductive system
The male reproductive system involves a variety of structures working to create and transport the male gamete cell (sperm).
What are the testes?
The testes are the site of sperm creation and development in the male reproductive system.
They are two oval-shaped organs that measure 4-5 cm in length and 2.5-3 cm in diameter
The testes are covered and protected by two tissues:
Tunica Vaginalis: the outer protective covering.
Tunica Albuginea: the inner fibrous coat or capsule. Extensions penetrate into the testis, dividing it into 250-300 lobules. Each lobule contains four thin and elongated seminiferous tubules.
What are the semniferous tubules?
Within the testes are tightly coiled seminiferous tubules that produce sperm. Each testis contains about 600-1000 seminiferous tubules in its lobules, which are 80 cm in length when uncoiled. In the loose connective tissue between these tubules, Leydig cells produce and secrete testosterone.
What is sperm?
Sperm are gametes of the male reproductive system that carry paternal genetic information.
Head: flat with an oval shape. It contains the nucleus, which contributes either an X or Y
chromosome to fertilization. The head also contains the acrosomal cap, which contains
enzymes to help the sperm penetrate the layers of the egg.
Neck: connects the head to the midpiece.
Midpiece: a continuation of the neck with a mitochondrial collar that helps produce energy.
Tail (flagellum): the source of movement for the sperm.
What is the scrotum?
The scrotum is the sac of skin and fascia surrounding the testes. It is derived from the anterior abdominal wall and resides outside of the abdominopelvic cavity.
There are two muscles in the scrotum that control the temperature of the testes.
Dartos Muscle: located superficially in the skin of the scrotum. It is responsible for the rugose appearance of the scrotal sac, and helps to regulate temperature by altering the exposed surface area of the scrotum.
Cremaster Muscle: a covering of the testis found deep to the scrotal wall. It contracts in a cold environment, drawing the testes superiorly in the scrotum, closer to the body wall to absorb body heat.
What is the epidymisis?
The epididymis is the first portion of the male duct system that lies on the superior and posterior border of each testis.
The epididymis measures 4 cm in length, but contains long coiled tubules (4-5 meters total
length).
Head: contains and receives sperm from the seminiferous tubules.
Body: contains the highly coiled duct of the epididymis.
Tail: where the coiling of the duct has diminished and the tube reverses its direction and ascends into the vas deferens. The tail is where sperm are
stored prior to ejaculation.
Histologically, the ducts of the epididymis are lined with pseudostratified columnar epithelium.
What is the vas deferens?
The vas deferens is the second portion of the male duct system. It stores and transports sperm from the
epididymis to the urethra.
The vas deferens is lined with pseudostratified columnar epithelium containing stereocilia. It has a small lumen, but a thick muscularis composed of smooth muscle. The thick muscular layer helps propel sperm through the vas deferens.
What structures are associated with the vas deferens?
Ampulla of Vas Deferens: the expanded distal portion of the vas deferens.
Ejaculatory Duct: formed by the
ampulla of the vas deferens and the duct of the seminal vesicle.
Seminal Vesicles: accessory glands that secretes nutritive fluid for sperm.
What are the accessory glands of the male reproductive system?
There are three accessory glands that nourish the sperm as they travel through the duct system.
Seminal vesicles: large, coiled, tubular glands that provide fluid and nutrients to the ejaculate and make up 60% of the volume of semen.
Prostate gland: the size of a walnut, consisting of tubular glands embedded in a mass of smooth muscle and connective tissue. It produces and secretes sugars and enzymes, which account for about 33% of the volume of the seminal fluid.
Prostatic fluid is rich in proteases, particularly prostate-specific antigen, that aid in liquefaction and
dissolution of cervical mucus in the female reproductive system.
Bulbourethral Glands: secrete a thick, clear, alkaline mucus that drains into the penile urethra. Secretion is released before ejaculation to neutralize traces of acidic urine in the urethra and to lubricate the urethra and penis.
What is the pathway of sperm?
Sperm is produced in the seminiferous tubules of the testes and transported through a series of ducts. From the testes, sperm passes through the epididymis, vas deferens,
ejaculatory duct, and urethra. Along its course through the male duct system fluid is secreted from glands that contribute to the volume of semen.
What is the penis?
The penis has both urinary and reproductive functions.
Root: fixed portion that attaches the penis to the ischium.
Body: tubular, moveable portion of the penis that consists of three cylinders of erectile tissues and contains
the urethra.
Glans: expanded distal end that contains the external urethral opening.
The penis is made up of two different types of erectile tissues. The two tissue types create three cylinders of tissue.
Corpora Cavernosa: two erectile cylinders on the dorsal surface of the penis, which make up most of the penis mass. The proximal portions of the corpora cavernosa are known as the crura and are attached to the bony pelvis by muscles.
Corpus Spongiosum: contains the urethra and expands distally to form the glans of the penis. The proximal
end is enlarged and called the bulb of the penis.
What is the female reproductive system?
The female reproductive system differs largely from the male reproductive system but there are some similarities between the two. Both systems are required in the creation of a fetus. The female reproductive system involves a variety of structures working in synchrony to produce the
female gamete cell, an ovum, and to carry a fetus to full term.
What are the ovaries?
The ovaries are paired organs located near the lateral walls of the pelvis. They measure 2 cm in length, and 1-1.5 cm in thickness. The ovaries are where ova are produced and stored prior to ovulation.
Various ligaments protect and anchor the ovaries. The ovaries are also protected by an outer covering of dense connective tissue.
- Ovarian Ligament: anchor the ovaries to the uterus.
- Suspensory Ligament: anchor the ovaries to the pelvic wall.
Similar to the testes, the ovaries are surrounded by a connective tissue capsule, known as the tunica albuginea.
Deep to the tunica albuginea, the ovaries are each divided into a cortex and medulla.
- Cortex: contains ovarian follicles. One mature follicle is ovulated during a menstrual cycle.
- Medulla: the inner region of the ovary that contains blood vessels, nerves, and lymphatics that supply the tissue of the ovary.
What are the stages of ovarian follicles?
Primordial follicle: the most immature of the follicles and is made up of single layer of squamous cells surrounding the oocyte.
Primary follicle: develops from the primordial follicle. This has two or more layers of cells
surrounding the egg.
Secondary follicle: develops next and is surrounded by many layers of cells. It also contains an antrum, or fluid-filled space. The secondary follicle is also known as the antral follicle.
Corpus Luteum: after ovulation, the corpus luteum develops from the remnants of the mature follicle.The corpus luteum mainly produces progesterone and estrogen (less) to support fertilization. If fertilization does not occur, the corpus luteum degenerates.
Graafian (tertiary) follicle: the mature follicle that will be ovulated. Ovulation is the rupture of a Graafian follicle, where it is ejected from the ovary - surrounded by multiple layers of cells and contains an antrum, but is larger relative to the secondary follicle.
What are the uterine tubes?
The uterine tubes are the ducts of the female reproductive system. They are also called the fallopian tubes, or oviducts, and measure 10-12 cm in length.
Infundibulum: the funnel-shaped, distal end that opens into the peritoneal cavity and has finger like fimbriae. The function of the infundibulum is to capture the egg after it is
released from an ovary.
Ampulla: the longest and widest portion where fertilization normally occurs.
Isthmus: the proximal portion that passes through the uterine wall, opening into the lumen of the uterus.
Whats the uterus?
The uterus is a pear-shaped muscular organ that carries and supports the developing fetus during pregnancy and contracts to eject the fetus during childbirth.
Fundus: the most superior portion of the uterus. It is dome shaped and extends between the uterine tubes.
Body: the main part of the uterus and is composed of smooth muscle.
Cervix: inferior portion that projects into the vagina. In the cervix, there is a cervical canal with two openings.
- Internal OS: connects uterus and cervix
- External OS: connects cervix and vagina
Explain the histology of the uterine wall
The uterine wall has three layers.
Endometrium: glandular inner lining of the uterus which undergoes changes throughout the menstrual cycle. The
endometrium makes up 10% of the total mass of the uterus.
Myometrium: middle layer of smooth muscle that makes up 90% of the total mass of the uterus.
Perimetrium: thin outer layer composed of serosa.
What is the broad ligament of the uterus?
The broad ligament drapes over and supports the uterus.
Whats the vagina?
The vagina is located inferior to the cervix, and it is approximately 10 cm in length.
It connects the uterus to outside the body and acts as the birth canal.
Mucosa: stratified squamous to produce glycogen, which is metabolized into lactic acid. This serves to protect the vagina by creating an acidic environment.
Muscularis: elastic and loose connective tissue, with an inner circular and very thick outer
longitudinal layer of smooth muscle.
The vagina is covered by an adventitia.
Which gland is responsible for secreting alkaline mucus into semen?
Bulbourethral Gland
Describe the external female genitalia
The external genitalia, also known as the vulva or pudendum, lies external to the vagina.
Mons Pubis: the adipose tissue overlying the pubic bone.
Clitoris
Labia Majora: two elongated, fatty folds of skin that are homologous to the male scrotum and bear pubic hair.
Labia Minora: two thin, fat free folds of skin close to the vestibule of the vagina. The labia minora are devoid of pubic hair.
Vestibule: space bounded by the labia minora. It bears the external urethral and vaginal openings.
What are mammary glands?
The mammary glands are modified sweat glands in the female that produce and secrete milk. They consist of 15-20 lobes that contain glands. Connective tissue separate the lobes and
function as the suspensory ligaments that attach the breast to the underlying muscle and overlying
skin. The mammary glands include the lactiferous ducts, which drain into the nipple and the pigmented area around the nipple, known as the areola.
