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Anatomy2x2Week7.pptxRespiratory & Urinary
System
Week 7- 2x2
LS of Epiglottis
The epiglottis is a flap made of elastic cartilage covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. It stands open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration, forcing the swallowed liquids or food to go down the esophagus instead. It is thus the valve that diverts passage to either the trachea or the esophagus.
The body consists of elastic cartilage. The epiglottis has two surfaces, a lingual and a laryngeal surface, related to the oral cavity and the larynx respectively.
The entire lingual surface and the apical portion of the laryngeal surface are covered by stratified squamous non-keratinized epithelium. However, some parts of the laryngeal surface has respiratory epithelium (pseudostratified ciliated columnar) cells and mucus secreting goblet cells.
During swallowing, elevation of the hyoid bone draws the larynx upward; as a result, the epiglottis folds down to a more horizontal position, with its superior side functioning as part of the pharynx. In this manner, the epiglottis prevents food from going into the trachea and instead directs it to the esophagus, which is at the back. Should food or liquid enter the windpipe due to the epiglottis failing to close properly, the gag reflex is induced to protect the respiratory system.
Cross Section of Trachea
The trachea, also called the windpipe, is a cartilaginous tube that connects the pharynx and larynx to the lungs, allowing the passage of air. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea the cricoid cartilage attaches it to the larynx. This is the only complete tracheal ring, the others being incomplete rings of reinforcing hyaline cartilage.
Frontal Section of larynx
The larynx, commonly called the voice box, is involved in breathing, producing sound, and protecting the trachea against food aspiration. The larynx houses the vocal cords, and manipulates pitch and volume, which is essential for phonation (phonation is the process by which the vocal folds produce certain sounds through quasi-periodic vibration). It is situated just below where the tract of the pharynx splits into the trachea and the esophagus.
The laryngeal skeleton consists of six cartilages: three single (epiglottic, thyroid and cricoid) and three paired (arytenoid, corniculate, and cuneiform). The hyoid bone is not part of the larynx, though the larynx is suspended from the hyoid. The larynx extends vertically from the tip of the epiglottis to the inferior border of the cricoid cartilage.
The thyroid cartilage forms the Adam's apple. It is usually larger in males than in females. The thyrohyoid membrane is a ligament associated with the thyroid cartilage that connects the thyroid cartilage with the hyoid bone.
The cricoid cartilage is a ring of hyaline cartilage that forms the inferior wall of the larynx. It is attached to the top of the trachea.
Respiratory Tract
Respiratory Pathway:
Oxygen rich air from environment travels into the nasal cavaties>pharynx>trachea>bronchi>bronchioles>alveoli>oxygen and carbon dioxide exchange occurs in alveoli>bronchioles>bronchi>trachea>pharynx>nasal cavaties>carbon dioxide rich air flows out to the environment
The bronchus, is a passage of airway in the respiratory tract that conducts air into the lungs. The first bronchi to branch from the trachea are the right main bronchus and the left main bronchus. These are the widest and enter the lungs at each hilum (indentation), where they branch into narrower secondary bronchi known as lobar bronchi, and these branch into narrower tertiary bronchi known as segmental bronchi. Further divisions of the segmental bronchi are known as 4th order, 5th order, and 6th order segmental bronchi, or grouped together as subsegmental bronchi. The bronchi when too narrow to be supported by cartilage are known as bronchioles. No gas exchange takes place in the bronchi.
The cartilage and mucous membrane of the primary bronchi are similar to those in the trachea. They are lined with respiratory epithelium. The epithelium in the main bronchi contains goblet cells. Mucus plays an important role in keeping the airways clear in the mucociliary clearance process. As branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the bronchioles. As the cartilage decreases, the amount of smooth muscle increases. The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium.
LS of Respiratory Bronchioles continuing into an alveolar duct
The respiratory bronchioles are the narrowest airways of the lungs, one fiftieth of an inch across. The bronchi divide many times before evolving into the bronchioles. The bronchioles deliver air to the exchange surfaces of the lungs. They are interrupted by alveoli. Alveolar ducts are distal continuations of the respiratory bronchioles.
Terminal Bronchiole to Respiratory Bronchiole
The terminal bronchiole is the most distal segment of the bronchioles. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Club cells are non-ciliated, rounded protein-secreting cells. Their secretions are a non-sticky, proteinaceous compound to maintain the airway in the smallest bronchioles. The secretion, called surfactant, reduces surface tension, allowing for bronchioles to expand during inspiration and keeping the bronchioles from collapsing during expiration. Club cells, a stem cell of the respiratory system, produce enzymes that detoxify substances dissolved in the respiratory fluid. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells.
Cross Section of Alveoli
An alveolus (pl. alveoli) is a hollow cavity found in the lungs and is the basic unit of ventilation. Lung alveoli are the ends of the respiratory tree, branching from either alveolar sacs or alveolar ducts, which like alveoli are both sites of gas exchange with the blood as well. The alveolar membrane is the gas exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the capillaries that surround the alveoli where, carbon dioxide is released and oxygen absorbed via diffusion.
The alveoli consist of an epithelial layer and an extracellular matrix surrounded by capillaries. The alveoli contain some collagen and elastic fibers. The elastic fibers allow the alveoli to stretch as they are filled with air during inhalation. They then spring back during exhalation in order to expel the carbon dioxide-rich air.
There are three major types of cell in the alveolar wall–two types of alveolar cell and a phagocyte:
Type I cells are thin and flat and form the structure of the alveoli
Type II cells secrete surfactant to lower the surface tension of water and allows the membrane to separate, therefore increasing its capability to exchange gases. Surfactant is continuously released by exocytosis. It forms an underlying aqueous protein-containing hypophase and an overlying phospholipid film composed primarily of dipalmitoyl phosphatidylcholine.
The phagocytes are macrophages, that destroy foreign material, such as bacteria.
Renal corpuscle
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Distal Tubule with Macula Densa
Epithelium of Bowman’s Capsule
Basement Membrane of Bowman’s Capsule
Beginning of Proximal Tubule
Nephron
The nephron is the functional unit of the kidney. Each nephron is composed of a renal corpuscle, the initial filtering component; and a renal tubule that processes and carries away the filtered fluid.
The renal corpuscle is the site of the filtration of blood plasma. The renal corpuscle consists of the glomerulus, and the Bowman's capsule (glomerular capsule). The renal corpuscle has two poles – a vascular pole and a urinary pole.
The arterioles from the renal circulation enter and leave the glomerulus at the vascular pole. The glomerular filtrate leaves the Bowman's capsule at the renal tubule at the urinary pole.
The glomerulus is the network of filtering capillaries located at the vascular pole of the renal corpuscle in the Bowman's capsule. Each glomerulus receives its blood supply from an afferent arteriole of the renal circulation. The glomerular blood pressure provides the driving force for water and solutes to be filtered out of the blood plasma, and into the space in Bowman's capsule.
Only about a fifth of the plasma is filtered in the glomerulus. The rest passes into an efferent arteriole. The diameter of the efferent arteriole is smaller than that of the afferent, and this difference increases the hydrostatic pressure in the glomerulus.
The Bowman's capsule, also called the glomerular capsule, surrounds the glomerulus. It is composed of a visceral inner layer formed by specialized cells called podocytes, and a parietal outer layer composed of simple squamous epithelium. Fluids from blood in the glomerulus are filtered through the visceral layer of podocytes, resulting in the glomerular filtrate.
The glomerular filtrate next moves to the renal tubule, where it is further processed to form urine. The different stages of this fluid are collectively known as the tubular fluid.
The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system.
Components of the renal tubule:
Proximal convoluted tubule, Loop of Henle (descending portion, ascending portion), distal convoluted tubule
The proximal tubule as a part of the nephron can be divided into an initial convoluted portion and a following straight (descending) portion. Fluid in the filtrate entering the proximal convoluted tubule is reabsorbed into the peritubular capillaries, including approximately two-thirds of the filtered salt and water and all filtered organic solutes (primarily glucose and amino acids)
The loop of Henle is a U-shaped tube that extends from the proximal tubule. It consists of a descending limb and an ascending limb. The primary role of the loop of Henle is to concentrate the salt in the interstitium (the tissue surrounding the loop). The descending limb is permeable to water and noticeably less permeable to salt, and thus only indirectly contributes to the concentration of the interstitium. The ascending limb is impermeable to water, a critical feature of the countercurrent exchange mechanism employed by the loop. The ascending limb actively pumps sodium out of the filtrate, generating the hypertonic interstitium that drives countercurrent exchange.
The distal convoluted tubule has a different structure and function to that of the proximal convoluted tubule. Cells lining the tubule have numerous mitochondria to produce enough energy (ATP) for active transport to take place. Much of the ion transport taking place in the distal convoluted tubule is regulated by the endocrine system. In the presence of parathyroid hormone, the distal convoluted tubule reabsorbs more calcium and secretes more phosphate. When aldosterone is present, more sodium is reabsorbed and more potassium secreted.
Each distal convoluted tubule delivers its filtrate to a system of collecting ducts, the first segment of which is the connecting tubule. The collecting duct system begins in the renal cortex (of the kidney) and extends deep into the medulla (of the kidney). As the urine travels down the collecting duct system, it passes by the medullary interstitium which has a high sodium concentration as a result of the loop of Henle's countercurrent multiplier system.
Blood from the efferent arteriole, containing everything that was not filtered out in the glomerulus, moves into the peritubular capillaries, tiny blood vessels that surround the loop of Henle and the proximal and distal tubules, where the tubular fluid flows. Substances then reabsorb from the latter back to the blood stream.
The peritubular capillaries then recombine to form an efferent venule, which combines with efferent venules from other nephrons into the renal vein, and rejoins the main bloodstream.
