Organ Architecture Classification of Organs and Membrane Structure PDF

Atoms —> molecules —> cells —> tissues —> organs (tissues together to serve a specific function/ functions) —> organ system System —> assembly of organs that are homogenous with respect to function, structure, embryological origin and prevailing tissue (es: muscular system, all muscles serve the sa...

Atoms —> molecules —> cells —> tissues —> organs (tissues together to serve a specific function/ functions) —> organ system System —> assembly of organs that are homogenous with respect to function, structure, embryological origin and prevailing tissue (es: muscular system, all muscles serve the same function and originate from the same tissue) Apparatus —> assembly of organs which concur to a common general function but that also have specific functions and morphology and are composed of tissues with dissimilar embryological origin Organs of the same system/apparatus are physically interconnected Organ classification Solid or Parenchymal —> they lack an internal cavity (es:liver), they are characterised by the presence of a stroma and a parenchyma, they can be parallel/elongated, fibrous or filamentous (es: muscles and nerves are organs) Layered organs —> 1. Hollow organs: the wall (layers of tissues) delimits a cavity (es: stomach and trachea). They can either be visceral (saccular or tubular according to the shape) or vascular (blood and lymphatic vessels are organs) 2. Skin (delimits the whole structure of the human body) SOLOD or PARENCHYMAL ORGANS They’re delimited by a capsule and are made of a stroma and parenchyma. There’s no cavity Capsule —> made of dense connective tissue (collagen, elastic fingers and sometimes smooth muscle cells). It delimits the organ, supports vessels and nerves, regulates organ volume (es: spleen that changes blood volume thanks to muscular fibers) and provides a site of attachment for ligaments Stroma —> either loose or dense connective tissue (collagen and elastic fibers), sometimes reticular connective tissue or muscular fibers. The stroma of an organ doesn’t contain a functional component of the organ, it is just the supporting framework that may also divide the organ in different compartments (septa and trabeculae form lobes or lobules). Vessels and nerves travel in the stroma so that it also serves an important tropic function. Its connective tissue is looser inside and denser out. Parenchyma —> they can be epithelial cells or other types of cells. The parenchyma of organs might be separated by septa or trabeculae of stroma. Here the functional features of the organ are contained Hilum —> thickening of the capsule, invagination that allows the passage of vessels, nerves and ducts fetalkidney spleen  kidney Parenchymal cells can either be homogeneously or adrenalgeena heterogeneously distributed a In highly cellular organs there might be a network of fibers that creates a reticulum supporting the cells pancreas liver Radiological appearance of solid organs —> the normal liver liver is homogeneous while the kidney is heterogenous pathologicalliver normal 9 kidney solid hollow The lungs are special solid organs (they’re filled with hair). Inside the lungs there is a tubing system (es: bronchi) which is considered a hollow organ abnormallungs normallungs Filamentous organs are made of elongated parallel multifunctional units like muscle fibers, collagen fibers and nerve fibers arranged into bundles and organised by connective tissues. Examples of filamentous organs are muscles, tendons and nerves ofanerve crosssection Tendons are made of collagen fibers HOLLOW ORGANS Their wall is made by tunicae (different layers) and it delimits a lumen. Hollow organs communicate directly or indirectly with the outside. Hollow organs are divided into visceral hollow organs and vascular hollow organs Visceral hollow organ The inner most layer (towards the lumen) is called mucosa or tunica mucosa, below the mucosa there is the submucosa, then the muscolaris externa (or muscolaris propria) and then a serosa or an adventitia (or both, serosa if they remain the serosal cavity, otherwhise only connective tissue called adventitia) Visceral tubular hollow organs: Mucosa —> membrane made by epithelium + lamina propria (loose connective tissue that contains fibroblasts, plasma cells, macrophages, leukocytes and mast cells). In the digestive tube there is the muscolaris mucosae (muscle layer that belongs to the mucosa) Submucosa —> typically made of loose connective tissue (it contains blood and lymphatic vessels, cells of the immune system and neurons) oesophagus Muscolaris externa —> arranged in 2 layers (circular inner layer and longitudinal outer layer, made of smooth muscle) Adventitia—> connective tissue Serosa (if the organ is in a serosal cavity) —> mesothelium + connective tissue A mucosa can be smooth or it can present folds (to increase surface area)  squamousstratified Invaginations of epithelia lining the mucosa form prevaostmengicaciriarea glands its anorgandictates wecontenthe function funciongonogenbylooking transitional simple atitsmucosa own extension glands of Glands can be present in the mucosa and unimprome submucosa and they can be also extramural (liver and pancreas). Es: byle is released by the liver in the duodenum even though it is not submucose located in the intestine (it just maintains a connection) gaubeaderer as Visceral saccular hollow organs —> the muscolaris propria has an organisation more difficult to distinguish while the submucosa is absent or poorly developed Vascular hollow organs Different tunicae (layers): tunica intima (endothelium + CT) —> tunica media (CT + smooth muscle cells) —> tunica adventitia (CT) Inner elastic lamina (between the tunica intima and media) and outer elastic lamina (between tunica media and adventitia) Differences between arteries and veins —> arteries contain lots of elastic fibers and their tunica media is thicker Skin (also classified as a cutaneous membrane): Squamous stratified epithelium —> keratinised in many places Dermis —> fibro-collagenous tissue and elastic fibers + vessels nerves and receptors. It is divided in a papillary layer (outermost, loose CT) and a reticular layer (innermost, dense CT). The subcutis (below dermis) are mainly adipose tissue Membranes in the body inmobilejoints MEMBRANES Mucous membranes —> they line the organs communicating with the outside and they are the innermost layer of hollow organs. The are humidified and lubricated by mucus, glandular secretions and other fluids. They’re made of an epithelium (on a basement membrane) and a lamina propria. Synovial membranes —> they’re made of connective tissue and they’re between the articular cavity and the joint capsule. Surface layer (intima): fibroblast-like synoviocytes and macrophages. Underlying tissue (subintima): loose CT, blood vessels, lymphatics, fibroblasts, collagen fibers, nerve fibers and extra cellular matrix. They’re lubricated (synovial fluid) Serous membrane —> mesothelium (flattened epithelium on basal membrane) and loose connective tissue. Lines ventral body cavities and surrounds some organs. It is very thin and it adheres to body cavities (parietal layer) and to surfaces of organs (visceral layer). They produce a liquid (lubricant). Serousal membranes reduce friction, avoid sticking of adjacent organs and allow them to move freely Some organs may be completely enveloped by serosa (like lungs) while other may only be partially enveloped. Intestine: the duodenum is not covered by serosa (it is reabsorbed) while most of the intestine is covered by it. What we know about an organ is gonna tell us something about how they will respond to a trauma. For example organs in the thoracic cavity may be more protected than those in the abdominal cavity (thanks to bones) but they can also be more at risk of puncturing due to bones shattering Trauma —> serious damage to body regions due to mechanical forces. It can be closed (blunt force trauma) or penetrating (an object pierces the skin or the body). Motor vehicle crashes cause over 1 million deaths per year (due to traumatic impacts) Position —> can guarantee more protection but more risks at the same time Type —> hollow or solid —> in blunt trauma solid organs are more likely to be damaged (they absorb more kinetic energy) State —> full hollow organs are injured more than empty hollow organs Mobility —> the more mobile an organ is the more it can move according to other organs Newton’s first law of motion —> a body in motion or a body at rest will remain in that site until acted upon by an outside force Law of conservation of energy —> energy can’t be created or destroyed, it can just change form Blunt trauma —> the transfer of energy produces damages to the body without penetrating it. Blunt trauma can change the characteristics of a organ Abdominal trauma is responsible for 10% of trauma induced death (leading cause of death under the age of 40) hematoma mane contusion blood inthe peritonealcavity bead poorbetween capsuleonaparenchymal Vehicular collision: when a vehicle collides three separate impacts will take place as a result First impact —> collision of the vehicle itself when the vehicle is brought to an abrupt stop, the kinetic energy is absorbed by the vehicle causing its deformation Second impact —> collision of the unrestrained occupants against the vehicle structure or other structures outside the vehicle if the victims are ejected. The forward motion of the occupants, travelling at the same speed of the car, continues as the vehicle comes to an abrupt stop. This motion is arrested when the passengers collide with part of the vehicle structure. Kinetic energy is absorbed partly by the car and partly by the occupant’s bodies. This may result in denting of the car structure and injuries to car occupants  Third impact —> patient’s organ collision against the body framework, it occurs then the victim’s body meets a stationary object. The organs move inside the cavities and collide against body structures. Deceleration forces cause the brain to move backwards colliding with the skull. Shear forces may be generated causing stretching and linear shearing between relatively fixed and free adjacent structures. During acceleration or deceleration the different consistency of different parts of the brain makes them to move at different speeds thus causing stretching of the neural axons Hollow organ injuries —> a trauma can cause a spillage of the infectious content of hollow organs thus producing a painful inflammatory reaction called peritonitis Penetrating trauma —> it can be caused by gun shot wounds, stab wounds or impalement Solid organs = more bleeding Hollow organs = inflammation Mechanisms that cause trauma in gunshots —> depends on the distance from the target, the shape/size of the bullet, the velocity of the bullet (most important), the surface area impacted (fragmentation of the bullet) and the anatomy involved Three types of damage inflicted by bullets: Laceration —> shredding of tissue/bone, most common of bullets moving at a low velocity. Fragmentation of bone can cause further damage Cavitations —> permanent cavity is caused by the path of the bullet, temporary cavity is formed by continued forward acceleration of the medium in the wake of the bullet, causing the wound cavity to be stretched outward Shock Waves —> air at te front and sides of a very fast moving bullet can become compressed, the explosive relaxation of the compression generates a damaging shock wave that can be several hundreds atmospheres in pressure. Fluid-filled organs can burst by pressure.