Ingegneria delle tecnologie per la salute

Fondamenti di anatomia e istologia

aa. 2017-18

Respiratory System

Sistema respiratorio

RESPIRATORY SYSTEM

• every human cell needs to run oxidative cellular respiration (=oxidative phosphorylation, process where energy is produced in the form of ATP) where oxygen is a reactant and carbon dioxide is a waste product

• it is actually the accumulation of carbon dioxide that primarily drives the need to breathe

• carbon dioxide is exhaled and oxygen is inhaled through the RS, which includes:

1.muscles to move air into and out of the lungs, 2.passageways through which air moves, and 3.microscopic gas exchange surfaces covered by capillaries.

RESPIRATORY SYSTEM

Functionally, RS divided in: conducting zone = organs and structures not directly involved in gas exchange respiratory zone = where gas exchange occurs

Major RS function: to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. RS also used for non-vital functions: sensing odors, speech production, and for straining, such as during childbirth or coughing

RESPIRATORY SYSTEM

Conducting Zone

major functions: to provide a route for

incoming and outgoing air, remove debris and

pathogens from the incoming air,

warm and humidify the incoming air.

other functions: epithelium of the nasal

passages is essential to sensing odors,

bronchial epithelium that lines the lungs can metabolize some airborne carcinogens.

Nose (+ its Adjacent Structures)

root = region located between the eyebrows bridge = part that connects the root to the

dorsum dorsum nasi = length of the nose apex = tip of the nose alae (singular = ala) = cartilaginous structure

on either side of the apex forming the nostrils naris (plural = nares), or nostril opening =

the “holes” philtrum = concave surface that connects the

apex of the nose to the upper lip nasal bone = one of a pair lying under the root

and bridge, articulating superiorly with frontal bone and laterally with maxillary bones.

septal cartilage = flexible hyaline cartilage connected to the nasal bone, forming the dorsum nasi.

alar cartilage = apex of the nose surrounding naris.

major entrance and exit for the RS through the nose, divided into 2 sections: 1. external nose = surface and skeletal structures outward appearance +

numerous functions

Nose (+ its Adjacent Structures)

Nose (+ its Adjacent Structures)

2. Nasal cavity = separated into left and right sections by the nasal septum

nasal septum = anteriorly by a portion of the septal cartilage and posteriorly by the perpendicular plate of the ethmoid and the vomer lateral walls = 3 bony projections, called the superior, middle, and inferior nasal conchae (turbinate), inferior conchae are separate bones, whereas the superior and middle conchae are portions of ethmoid. floor = palate (hard palate at the anterior region composed of bone + soft palate at the posterior portion consists of muscle tissue)

Nose (+ its Adjacent Structures)

Vomeronasal organ (Jacobson’s)

Nose (+ its Adjacent Structures)

paranasal sinuses = air-containing spaces lined with a mucosa in the bones that form the walls of the nasal cavity, serving to warm and humidify incoming air, producing mucus and lightening the weight of the skull, named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus

Nose (+ its Adjacent Structures)

• olfactory epithelium is located in the roof of the nasal cavity, on each side of the dividing septum, and on the surface of the superior concha. The olfactory epithelium is specialized for the reception of smell. Pseudostratified tall columnar epithelium without goblet cells and without motile cilia. The underlying lamina propria contains olfactory (Bowman) glands producing a serous secretion. Small nerves that are located in the lamina propria are the olfactory nerves

• Other conchae, meatuses, and paranasal sinuses lined by respiratory epithelium composed of pseudostratified ciliated columnar epithelium + goblet cells cilia of the respiratory epithelium help remove the mucus and debris with a constant beating motion, sweeping materials towards the throat to be swallowed

histology

Serous and mucus-producing cells also secrete the lysozyme enzyme and proteins called defensins, with antibacterial properties and immune cells that patrol the connective tissue deep to the respiratory epithelium provide additional protection

Nose (+ its Adjacent Structures) histology

Nose (+ its Adjacent Structures) histology

Nose (+ its Adjacent Structures) histology

Pharynx

= tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities, divided into 3 major regions:

1. Nasopharynx 2. Oropharynx 3. Laryngopharynx

Pharynx

Nasopharynx = flanked by the conchae, shows at the top the pharyngeal tonsil (= adenoid, aggregate of lymphoid reticular tissue), down the uvula (= small bulbous, teardrop-shaped structure located at the apex of the soft palate) and an opening of auditory (Eustachian) tubes

Pharynx

Eustachian Tube

Pharynx Eustachian Tube

Bartolomeo Eustachi meglio conosciuto come Eustachio (San Severino Marche, 1500-1510 – Fossombrone, 27 agosto 1574) è stato un anatomista italiano. Redige e completa tutti i suoi scritti sulla base di osservazioni ed esperimenti. Inaugura quell'anatomia sottile, proemio a quella microscopica. Teorizzò lo studio della tuba auditiva destra, ricordata tutt'oggi come la Tromba di Eustachio. Individuò inoltre le valvole coronarie, precisò ulteriormente la struttura di alcune ossa craniche, inietta di acqua calda le arterie renali, cercò di determinare la struttura dei reni e dei denti. Descrisse per la prima volta le ghiandole surrenali e fu il primo scopritore della vena alba, ora dotto toracico. Indaga con acutezza e logica lungimiranza sui cadaveri per malattie varie.

Pharynx

Oropharynx = passageway for both air and food, bordered superiorly by the nasopharynx and anteriorly by the oral cavity (fauces) nasopharynx becomes oropharynx, epithelium changes from pseudostratified ciliated columnar to stratified squamous epithelium, contains 2 distinct sets of tonsils, the palatine and lingual tonsils.

Pharynx tonsils

Tonsils are collections of lymphoid tissue facing into the aerodigestive tract. The set of lymphatic tissue known as Waldeyer's tonsillar ring includes the adenoid tonsil, two palatine tonsils, and the lingual tonsil. When used unqualified, the term most commonly refers specifically to the palatine tonsils, which are masses of lymphatic material situated at either side at the back of the human throat. The palatine tonsils and the nasopharyngeal tonsil are lymphoepithelial tissues located near the oropharynx and nasopharynx (parts of the throat).

Pharynx

Laryngopharynx = inferior to the oropharynx and posterior to the larynx, anteriorly opens into the larynx, whereas posteriorly, it enters the esophagus, stratified squamous epithelium continues

Pharynx

Larynx

= cartilaginous structure inferior to the laryngopharynx connecting pharynx to the trachea, regulating the volume of air that enters and leaves the lungs and producing speech, made of several pieces of cartilage, 3 large cartilage pieces: a) thyroid cartilage (anterior), largest piece of cartilage that makes up the larynx, consists of the laryngeal prominence, or “Adam’s apple,” which tends to be more prominent in males, b) epiglottis (superior), c) cricoid cartilage (inferior), thick cartilage forms a ring, with a wide posterior region and a thinner anterior region 3 smaller paired cartilages: a) arytenoids, b) corniculates c) cuneiforms—attach to the epiglottis and the vocal cords and muscle thathelp move the vocal cords

Larynx

Larynx

Il pomo d'Adamo è l'espressione con cui si designa comunemente la sporgenza della cartilagine tiroidea che circonda la laringe, che si osserva in alcuni individui pùberi e adulti in genere di sesso maschile, sulla linea mediana del collo. Nel linguaggio medico viene definito prominenza laringea. L'espressione trae origine da un'immagine di origine popolare, secondo la quale un boccone del frutto mangiato da Adamo gli sarebbe rimasto incastrato in gola.

Larynx

Larynx

Larynx

Epiglottis = very flexible piece of elastic cartilage attached to thyroid cartilage, covering the trachea opening, resting on the glottis. Glottis = composed of: a) vestibular folds or false vocal cord = a pair of folded sections of mucous membrane, b) true vocal cords = white, membranous folds attached by muscle to the thyroid and arytenoid cartilages of the larynx on their outer edges, and the space between these folds

Inner edges of the true vocal cords are free, allowing oscillation to produce sound. act of swallowing causes pharynx and larynx to lift upward, allowing pharynx to expand and epiglottis of the larynx to swing downward, closing the opening to the trachea. These movements produce a larger area for food to pass through, while preventing food and beverages from entering the trachea.

Larynx

Larynx

Larynx

Larynx histology

Continuous with laryngopharynx, larynx’ superior portion is lined by stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Similar to the nasal cavity and nasopharynx, this specialized epithelium produces mucus to trap debris and pathogens as they enter the trachea: cilia beat mucus upward towards laryngopharynx, where it can be swallowed down (esophagus).

Larynx

histology

Trachea

= extending from larynx to lungs, formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage that are connected by dense connective tissue (providing structural support and preventing the trachea from collapsing) + fibroelastic membrane (formed by trachealis muscle and elastic connective tissue together) a flexible membrane that closes the posterior surface of the trachea, connecting the C-shaped cartilages, allowing the trachea to stretch and expand slightly during inhalation and exhalation.

lined with pseudostratified ciliated columnar epithelium

Trachea

histology

Trachea

Bronchial Tree

Trachea branches into the right and left primary bronchi (still lined by pseudostratified ciliated columnar epithelium containing mucus-producing goblet cells, with rings of cartilage, similar to those of the trachea, supporting their structure and preventing their collapse: enter the lungs at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter lungs) at the carina (= raised structure containing specialized nervous tissue inducing violent coughing if foreign body is present).

Bronchi continue to branch into bronchial tree (or respiratory tree = collective term used for multiple-branched bronchi) providing passageway for air to move into and out of each lung and trapping debris and pathogens.

Bronchiole (about 1 mm in ) branches from the tertiary bronchi and further branch until terminal bronchioles (more than 1000 in each lung, simple columnar epitelium) leading to the structures of gas exchange and their muscular walls do not contain cartilage like those of bronchi. This muscular wall can change the size of the tubing to increase or decrease airflow through the tube.

Bronchial Tree

Bronchial Tree histology

Bronchial Tree histology

Bronchial Tree histology

Bronchial Tree histology

Respiratory Zone = includes structures that are directly involved in gas exchange, beginning where the terminal bronchioles join a respiratory bronchiole (smallest type of bronchiole), which then leads to an alveolar duct, opening into a cluster of alveoli.

Respiratory Zone histology

Respiratory Zone histology

Alveoli alveolar duct = tube of smooth muscle and connective tissue, which opens into a cluster of alveoli. alveolar sac = cluster of many individual alveoli alveolus = one of the many small, grape-like sacs connected to the alveolar ducts responsible for gas exchange, approximately 200 µm with elastic walls that allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange and connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the alveoli and lung

Alveoli alveolar wall = 3 cell types: 1. type I alveolar cell = squamous epithelial cell of the alveoli, which constitute up to 97 % of the

alveolar surface area, 25 nm thick, highly permeable to gases, attached to a thin elastic basement membrane

2. type II alveolar cell = (club cells, Clara cells) interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins reducing surface tension of alveoli

3. alveolar macrophage = phagocytic cell of the immune system roaming around the alveolar wall that removes debris and pathogens

histology

respiratory membrane =

extremely thin epithelium borders endothelial membrane of capillaries, 0.5 mm thick, allowing gases to cross by simple diffusion, allowing oxygen to be picked up by the blood for transport and CO to be released into the air of the alveoli.

Alveoli histology

Club cells…

Club cells previously called Clara cells, as first described by Max Clara (1899–1966), in 1937. Clara (active member of Nazi Party) used tissue taken from executed victims of Third Reich for his research, including that leading to discovery of Clara cells [1].

In May 2012, editorial boards of most of major respiratory journals concluded that the continued use of Clara's eponym would be equivalent to honoring him, therefore introducing a name-change policy, which went into effect beginning January 1, 2013 [2].

The term "Clara" was to be used parenthetically after "club cell" for a 2-year period, at which point when "Clara cell" and "Clara cell secretory protein" were conclusively replaced with "club cell" and "club cell secretory protein", respectively [3].

1. Winkelmann A. et al. (2010). "The Clara cell - a "Third Reich eponym"?". European Respiratory Journal 36 (4): 722–7. 2. Irwin RS et al. (2013). "Spread the word about the journal in 2013: from citation manipulation to invalidation of patient-reported outcomes

measures to renaming the Clara cell to new journal features". Chest 143: 1–5. 3. Akram KM et al. (2013). "Club cells inhibit alveolar epithelial wound repair via TRAIL-dependent apoptosis". Eur Respir J 41: 683–694.

Alveoli histology

Alveoli histology

Lungs

= houses structures of both the conducting and respiratory zones, their main function to perform the exchange of respiratory gases across a very large epithelial surface area—about 70 square mts—that is highly permeable to gases.

= pyramid-shaped, paired organs connected to the trachea by the right and left bronchi and enclosed by the pleurae, which are attached to the mediastinum; on inf surface, lungs are bordered by the diaphragm (= flat, dome-shaped muscle located at the base of the lungs and thoracic cavity); right lung is shorter and wider than left, and left lung occupies a smaller volume than right; cardiac notch = indentation on the surface of the left lung allowing space for the heart; apex of the lung is superior region, whereas base is opposite region near the diaphragm, costal surface of lung borders ribs and mediastinal surface faces midline; composed of smaller units = lobes (right lung 3 lobes: sup, middle, and inf; left lung 2 lobes: sup and inf), separated by fissures. Bronchopulmonary segment = division of a lobe, each receiving air from its own tertiary bronchus and supplied with blood by its own artery. Pulmonary lobule = subdivision formed by terminal bronchioles and their branches, separated by interlobular septum (=wall, composed connective tissue)

Gross Anatomy

Lungs

Lungs

Lungs

Bronchopulmonary segment

Lungs

Lungs

Blood Supply Being major function of the lungs performing blood supply containing deoxygenated blood, traveling to the lungs where red blood cells pick up o2 to be transported to tissues throughout the body, pulmonary artery arises from the pulmonary trunk carrying deoxygenated arterial blood to the alveoli and branching multiple times as it follows the bronchi, becoming progressively smaller in diameter; one arteriole accompanied by venule supply drain one pulmonary lobule, becoming pulmonary capillary network, as they near the alveoli, consisting of tiny vessels with very thin walls that lack smooth muscle fibers, creating the respiratory membrane: once blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs through the hilum.

Lungs

Blood Supply Bronchial artery

Lungs

Nervous Innervation Dilation and constriction of the airway are achieved through nervous control by the parasympathetic ( bronchoconstriction) and sympathetic (bronchodilation) nervous systems: reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels.

Pleura

Each lung is enclosed within a cavity that is surrounded by the pleura (plural = pleurae) = serous membranes surrounding lungs, separated by the mediastinum. pleurae consist of 2 layers: 1. visceral pleura = layer that is superficial to the lungs, and extends into and lines the lung fissures; 2. parietal pleura = outer layer connected to the thoracic wall, the mediastinum, and the diaphragm; visceral and parietal pleurae connect to each other at the hilum; pleural cavity = space between visceral and parietal layers.

Pleura

Pleura histology

The visceral pleural surface is seen here at high power, with a normal mesothelial surface of low cuboidal cells. There is a thin layer of connective tissue, below which are peripheral alveolar walls and alveoli. Between the visceral pleura covering the lung and the parietal pleura on the chest wall is a potential pleural space that is ordinarily filled with only a few cc's of serous fluid.

Mesoderm origin!

Diaphragm

= dome-shaped curved upwards structure of muscle and fibrous tissue separating thorax from abdomen, with peripheral attachments to abdominal and chest walls, from which muscle fibres converge in a central tendon (crest of the dome); emerges from many surrounding structures: ant xifoid and along costal margin, lat ribs 6-12, post vertebra at T12 (+ 2 appendages, the right and left crus, descend and insert at L1 & L2) with 2 lumbocostal arches, medial and lateral, on either side.

Diaphragm

primarily innervated by phrenic nerves formed from cervical nerves C3, C4 and C5, while the central portion of the diaphragm sends sensory afferents via the phrenic nerve, the peripheral portions of the diaphragm send sensory afferents via the intercostal (T5-T11) and subcostal nerves(T12).

Hiccup = reflex causes a strong contraction of the diaphragm followed about

0.25 seconds later by closure of the vocal cords, which results in the classic "hic" sound

1. Clearance of air from stomach A recent explanation by Howes in 2012: hiccups may have evolved along with other reflexes developed in mammals that allow them to coordinate suckling milk and breathing. Hiccups are only found in mammals, and are most common in infants, becoming rarer as mammals age. This may suggest that they evolved to allow air trapped in the stomach of suckling infants to escape, allowing more milk to be ingested. The hypothesis suggests that the air bubble in the stomach stimulates the sensory limb of the reflex at receptors in the stomach, esophagus and along the diaphragm. This triggers the hiccup, which creates suction in the chest, pulling air from the stomach up and out through the mouth, effectively burping the animal. This theory is supported by the strong tendency for infants to get hiccups, the component of the reflex that suppresses peristalsis in the esophagus, and the existence of hiccups only in milk-drinking mammals.

Evolutionary causes

Howes, D. (2012). "Hiccups: A new explanation for the mysterious reflex". BioEssays. 34 (6): n/a. doi:10.1002/bies.201100194

hiccup

2. Phylogenetic hypothesis An international respiratory research group composed of members from Canada, France and Japan proposed that the hiccup is an evolutionary remnant of earlier amphibian respiration.[12] Amphibians such as tadpoles gulp air and water across their gills via a rather simple motor reflex akin to mammalian hiccuping. The motor pathways that enable hiccuping form early during fetal development, before the motor pathways that enable normal lung ventilation form. Thus, the hiccup is evolutionarily antecedent to modern lung respiration. Additionally, this group points out that hiccups and amphibian gulping are inhibited by elevated CO2 and may be stopped by GABAB receptor agonists, illustrating a possible shared physiology and evolutionary heritage. These proposals may explain why premature infants spend 2.5% of their time hiccuping, possibly gulping like amphibians, as their lungs are not yet fully formed.

Evolutionary causes

Straus C, Vasilakos K, Wilson RJ, Oshima T, Zelter M, Derenne JP, Similowski T, Whitelaw WA (February 2003). "A phylogenetic hypothesis for the origin of hiccough". BioEssays. 25 (2): 182–188. doi:10.1002/bies.10224. Jump up ^ P. Kahrilas and G. Shi (1997). "Why do we hiccup?". Gut. 41 (5): 712–713. doi:10.1136/gut.41.5.712. PMC 1891574Freely accessible.