Name: bronchial branching and airflow control
Uploaded: 2025-05-22T09:06:18.000Z
Duration: 1 min 23 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

Absorption And Excretion

Respiratory System

The Bronchial Tree

An der Carina, die sich an der oberen Grenze des fünften Brustwirbels befindet, teilt sich die Luftröhre in die rechte und die linke Primärbronchie, die jeweils zur jeweiligen Lunge führen. Der rechte Primärbronchus ist kürzer, breiter und vertikaler als der linke.
Ähnlich wie die Luftröhre bestehen beide primären Bronchien aus unvollständigen Knorpelringen und einer flimmerigen, pseudogeschichteten säulenförmigen Epithelauskleidung.
Beim Eintritt in die Lunge verzweigt sich jeder primäre Bronchus in kleinere lappenförmige oder sekundäre Bronchien, wobei ein Bronchus jeden Lappen in beiden Lungen bedient.
Diese lappenförmigen Bronchien verzweigen sich in kleinere segmentale Bronchien, die spezifische bronchopulmonale Segmente innerhalb der Lappen versorgen.
Die Segmentierung setzt sich fort und bildet Bronchiolen, die sich in terminale Bronchiolen verzweigen und das Ende der leitenden Zone des Bronchialbaums markieren.
Die Bronchiolen enthalten Keulzellen oder Clara-Zellen, eine Art nicht-ciliatisierter Säulenzellen, die sich gegen eingeatmete Toxine verteidigen, Tensid produzieren und als Stammzellen fungieren können.
Darüber hinaus weisen die Äste des Bronchialbaums ein flimmerndes säulenförmiges und quaderförmiges Epithel, schleimproduzierende Becherzellen und einen höheren Anteil an glatter Muskulatur auf.

bronchialbaum

Die menschlichen Bronchien und der Bronchialbaum spielen eine entscheidende Rolle im Atmungssystem, da sie den Austausch von Sauerstoff und Kohlendioxid erleichtern. Im Folgenden werden die komplizierte Struktur und die Funktionen dieser Atmungskomponenten näher erläutert.

Die Trachea, allgemein als Luftröhre bekannt, ist ein Schlauch, der den Kehlkopf (Stimmapparat) mit den Bronchien verbindet. An einem Punkt, der Carina genannt wird, gabelt sie sich in zwei Hauptbronchien. Der rechte Hauptbronchus ist breiter, kürzer und vertikaler als der linke Hauptbronchus. Dieser anatomische Unterschied führt häufig zu einer höheren Inzidenz von Fremdkörperaspiration und Infektionen in der rechten Lunge.

Die Carina befindet sich am Verzweigungspunkt und ist ein Knorpelkamm, der dazu beiträgt, die Durchlässigkeit der Atemwege zu gewährleisten. Sie besitzt außerdem eine hohe Dichte an Hustenrezeptoren, wodurch sie sehr empfindlich auf Reizstoffe reagiert und einen Hustenreflex auslöst, um die Atemwege freizumachen.

Die Hauptbronchien teilen sich weiter in Nebenbronchien oder Lappenbronchien auf, wobei sich drei rechts (obere, mittlere und untere) und zwei links (obere und untere) befinden. Diese Lappenbronchien führen in die Lunge und versorgen bestimmte Lappen mit Luft.

Die Lappenbronchien verzweigen sich weiter in Segmentbronchien, auch tertiäre Bronchien genannt. Diese Segmentbronchien versorgen bestimmte Segmente innerhalb jedes Lappens mit Luft und sorgen so für eine effiziente Luftstromverteilung in der Lunge.

Weiter unten im Bronchialbaum teilen sich die Segmentbronchien in kleinere Bronchiolen. Diese Bronchiolen haben keinen Knorpel und bestehen überwiegend aus glatter Muskulatur. Die glatte Muskulatur ermöglicht die Bronchodilatation und Bronchokonstriktion und reguliert den Luftstrom je nach Bedarf des Körpers.

Außerdem teilen sich diese Bronchiolen weiter in immer kleinere Röhren. Zudem umfasst der Bronchialbaum auch Endbronchiolen, Atembronchiolen sowie Alveolargänge und Alveolen. Die Alveolen sind winzige Luftsäcke, in denen der eigentliche Gasaustausch stattfindet, wodurch Sauerstoff in den Blutkreislauf gelangt und Kohlendioxid ausgeschieden wird.

Im gesamten Bronchialbaum unterliegen die Strukturen erheblichen Veränderungen in ihrer Zusammensetzung. So besteht die Schleimhaut in den Hauptbronchien aus pseudostratifizierten Zylinderepithel. Diese Zusammensetzung ändert sich in den größeren Bronchiolen zu pseudostratifizierten säulenförmigen Flimmerepithel mit Becherzellen, in den kleineren Bronchiolen zu einfachen quaderförmigen Flimmerepithel ohne Becherzellen und in den terminalen Bronchiolen zu einfachen quaderförmigen Epithel ohne Flimmerhärchen. Diese Schleimhautschicht trägt zur Befeuchtung und Filterung der eingeatmeten Luft bei und hält Fremdpartikel und Krankheitserreger zurück.

Die Submukosa liegt unter der Schleimhaut und enthält Drüsen, die Schleim produzieren, der zum Auffangen und Entfernen schädlicher Partikel erforderlich ist. Darüber hinaus enthält die Submukosa Blutgefäße, Nerven und Lymphgefäße, die zur Gesamtfunktion des Bronchialbaums beitragen. Knorpel bieten den größeren Atemwegen wie der Luftröhre, den Hauptbronchien und den Lappenbronchien strukturelle Unterstützung. Tiefer im Bronchialbaum nimmt der Knorpel jedoch allmählich ab und glatte Muskeln werden zum vorherrschenden Bestandteil. Diese Verschiebung ermöglicht eine erhöhte Flexibilität und Kontrolle des Luftstroms in den kleineren Atemwegen.

Verschiedene Störungen oder Krankheiten können den Bronchialbaum beeinträchtigen und zu Atemwegskomplikationen führen. Asthma ist eine chronische Erkrankung, die durch Entzündungen und Verengungen der Atemwege gekennzeichnet ist, was zu Atembeschwerden führt. Die chronisch obstruktive Lungenerkrankung (COPD) bezeichnet eine Gruppe fortschreitender Lungenerkrankungen wie chronische Bronchitis und Emphyseme, die eine langfristige Behinderung der Atemwege verursachen. Weitere Erkrankungen sind Bronchitis, Bronchiektasen und Bronchiolitis, die jeweils unterschiedliche Symptome und Behandlungsstrategien aufweisen.

Das Verständnis der Struktur und Funktion der menschlichen Bronchien und des Bronchialbaums bietet wertvolle Einblicke in die komplexe Funktionsweise des Atmungssystems.

Bronchialbaum

An der Carina, die sich an der oberen Grenze des fünften Brustwirbels befindet, teilt sich die Luftröhre in die rechte und die linke primäre Bronchie, die jeweils zu ...

Education

Lehre

JoVE Core

Anatomy and Physiology

Anatomie und Physiologie

Unit 1

Einheit 1

The Respiratory System

Das Atmungssystem

KEY TERMS AND CONCEPTS

ZENTRALE BEGRIFFE UND KONZEPTE

bronchial branching and airflow control

The bronchial tree carries air from the trachea into the lungs and helps control breathing. The trachea, or windpipe, connects the larynx to the bronchi. At the carina, the trachea splits into two primary bronchi. The right primary bronchus is wider, shorter, and more vertical than the left. Because of that shape, foreign objects and infections are more likely to enter the right lung.

The carina is a cartilaginous ridge at the split in the airway. It helps keep the airway open. It also has many cough receptors, so it is very sensitive to irritants and can trigger a cough to clear the airways.

The primary bronchi branch into secondary, or lobar, bronchi. The right lung has three lobar bronchi: superior, middle, and inferior. The left lung has two: superior and inferior. These lobar bronchi enter the lungs and carry air to specific lobes. They then divide into segmental, or tertiary, bronchi that supply air to specific segments within each lobe.

Deeper in the bronchial tree, the segmental bronchi become smaller bronchioles. Bronchioles do not have cartilage. They are mostly made of smooth muscle. This muscle allows bronchodilation and bronchoconstriction, which changes airflow based on the body’s needs. The airways continue to branch into smaller tubes, including terminal bronchioles, respiratory bronchioles, alveolar ducts, and alveoli. The alveoli are tiny air sacs where gas exchange happens. Oxygen enters the bloodstream, and carbon dioxide leaves the body.

The airway lining also changes as the bronchial tree branches. The mucosa in the main bronchi is pseudostratified columnar epithelium. In larger bronchioles, it becomes ciliated pseudostratified columnar epithelium with goblet cells. In smaller bronchioles, it becomes ciliated simple cuboidal epithelium without goblet cells. In terminal bronchioles, it becomes nonciliated simple cuboidal epithelium. This mucosal layer helps humidify and filter inhaled air while trapping particles and pathogens.

Beneath the mucosa is the submucosa. It contains glands that make mucus, which helps trap and remove harmful particles. The submucosa also contains blood vessels, nerves, and lymphatics. Larger airways such as the trachea, primary bronchi, and lobar bronchi have cartilage for support. Farther into the bronchial tree, cartilage decreases and smooth muscle becomes more important. This shift gives the smaller airways more flexibility and control over airflow.

Several diseases can affect the bronchial tree and make breathing harder. Asthma is a chronic condition that causes airway inflammation and narrowing. Chronic obstructive pulmonary disease, or COPD, includes progressive lung diseases such as chronic bronchitis and emphysema. Other conditions include bronchitis, bronchiectasis, and bronchiolitis. Learning the structure of the human bronchi and bronchial tree helps explain how the respiratory system works.

Bronchial Branching and Airflow Control

overview of respiratory system

How Breathing Moves Air and Gases

The respiratory system moves air in and out of the body and exchanges oxygen and carbon dioxide with the environment. This gas exchange is part of respiration, which is essential for life. The system supplies the blood with oxygen so it can carry that oxygen to the rest of the body. Breathing starts when air enters through the nose or mouth. The nose and nasal cavity form the main external opening and the first part of the airway. Air then passes through the pharynx, or throat, which is shared...

nose and nasal cavity

How the Nose Filters and Senses Air

The nose filters, warms, moistens, and senses the air that enters the body. It also helps shape speech as sound vibrations pass through its large air spaces. The nose has an external part that is visible on the face and an internal part called the nasal cavity. The external nose is built from bone and hyaline cartilage, which gives it flexibility. It is covered by skin and muscle and lined with a mucous membrane. The frontal bone, nasal bones, and maxillary bone support this structure. The...

pharynx

Pharynx Pathways for Air and Food

The pharynx is a muscular tube lined with mucous membrane that connects the nasal cavities to the throat. It is divided into three parts: the nasopharynx, oropharynx, and laryngopharynx. Each part has a different role in moving air and food through the upper throat. The nasopharynx sits behind the nasal cavity and serves only as an air passage. Its upper region contains the pharyngeal tonsils, also called adenoids. These are clusters of lymphoid reticular tissue, similar to a lymph node, and...

larynx

Voice Box Anatomy and Function

The larynx is the voice box in the neck. It carries air into the lungs and helps produce voice. Its structure is complex because it must support both breathing and sound production. The larynx contains cartilage, muscles, and the vocal cords, also called vocal folds. It includes three large unpaired cartilages: the thyroid, cricoid, and epiglottis. It also includes three paired cartilages: the arytenoids, corniculates, and cuneiforms. Ligaments and membranes hold these parts together. The...

trachea

Trachea: Layers, Rings, and Airflow

The trachea is the windpipe, and it is a key airway in the human respiratory system. It carries air between the larynx and the bronchi so oxygen can reach the lungs. About half of the trachea lies in the neck, and it sits in front of the esophagus. In an average adult, the trachea is about 10 to 12 cm long. It extends from the larynx at the level of the sixth cervical vertebra to the level of the fifth thoracic vertebra. Its wall is supported by C-shaped cartilaginous rings. The back side is...

the bronchial tree

The bronchial tree carries air from the trachea into the lungs and helps control breathing. The trachea, or windpipe, connects the larynx to the bronchi. At the carina, the trachea splits into two primary bronchi. The right primary bronchus is wider, shorter, and more vertical than the left. Because of that shape, foreign objects and infections are more likely to enter the right lung. The carina is a cartilaginous ridge at the split in the airway. It helps keep the airway open. It also has...

alveoli and alveolar ducts

How Alveoli Enable Gas Exchange

The respiratory zone of the human body is where gas exchange happens. It begins when the terminal bronchioles branch into respiratory bronchioles, the smallest bronchiole type. These then lead into alveolar ducts and finally into clusters of alveoli. Alveoli are tiny air sacs that look like bunches of grapes. They connect to alveolar ducts, and a group of alveoli forms an alveolar sac. A single alveolus is about 200 μm wide, and its elastic shape lets it expand during inhalation. Nearby...

gross anatomy of the lungs

Lung Lobes, Airways, and Blood Flow

The lungs are paired organs that connect to the trachea through the left and right bronchi. Their base rests against the diaphragm, the dome-shaped muscle below the lungs. The lungs are covered by the pleurae and sit next to the mediastinum, the central space in the chest. The right lung is shorter and wider than the left lung, and it has a larger volume. The left lung has a cardiac notch, which is an indentation for the heart. The top of each lung is the apex, and the lower part is the base.

pleura of the lungs

Pleura Layers and Lung Protection

The pleura are membranes that protect the lungs inside the chest cavity. They are a type of serous membrane and wrap around each lung. The pleura have two layers: the visceral pleura and the parietal pleura. The visceral pleura covers the surface of the lung. The parietal pleura is the outer layer. It lines the thoracic wall, the mediastinum, and the diaphragm. The hilum is the point where the visceral and parietal layers connect. The space between these layers is called the pleural cavity. <br...

pressure relationships in thoracic cavity

pressure-relationships-in-thoracic-cavity

How Pressure Drives Breathing in the Lungs

Breathing depends on pressure changes in the lungs, chest, and airways. Pulmonary ventilation is the movement of air into and out of the lungs. It is driven by atmospheric pressure, intra-alveolar pressure inside the alveoli, and intrapleural pressure in the pleural cavity. Inhalation and exhalation rely on pressure differences between the atmosphere and the lungs. Gas pressure comes from the movement of confined molecules. Boyle’s law explains that pressure and volume are inversely...

pulmonary ventilation: inhalation

Pulmonary Ventilation and Breathing Pressures

Pulmonary ventilation depends on breathing movements and the pressure changes that move air into and out of the lungs. It supports the exchange of oxygen and carbon dioxide by letting the body take in oxygen and remove waste carbon dioxide. Boyle's law is important here because changes in volume and pressure affect how air moves in the respiratory system. Several respiratory volumes help describe how much air the lungs move. Tidal volume is the air inspired or expired during normal, quiet...

pulmonary cycle: exhalation

Exhalation and Lung Pressure Changes

Exhalation is the process of expelling air from the lungs. It depends on pressure differences between the lungs and the atmosphere. During normal quiet breathing, exhalation is passive and does not require muscle contraction. The elastic recoil of the lungs and chest wall helps both structures return to their resting positions after inhalation. When the muscles used for inhalation stop working, the diaphragm and external intercostal muscles relax. The diaphragm moves upward, and the ribs move...

factors affecting pulmonary ventilation

What Changes Breathing Ease in the Lungs

Breathing ease in the lungs depends on alveolar surface tension, lung compliance, and airway resistance. These factors affect how hard it is to move air during pulmonary ventilation, along with the pressure difference between the outside environment and the lungs. Alveolar surface tension comes from the fluid lining the inside of the alveoli. Water molecules in this fluid attract each other more strongly than they attract the air, so the liquid tends to pull the alveoli inward. That force must...

respiratory volumes and capacities

Lung Volume Measurements in Breathing

Lung volume measurements show how air moves in and out of the respiratory system during breathing. They help explain how the body takes in oxygen and removes carbon dioxide. Respiratory volumes and capacities also give useful information about lung function. Tidal volume is the air breathed in and out during normal, quiet breathing. Inspiratory reserve volume is the extra air that can be forcefully inhaled beyond tidal volume. Expiratory reserve volume is the extra air that can be forcefully...

physical principles governing gas exchange

physical-principles-governing-gas-exchange

Gas Laws in Lung Gas Exchange

Gas laws explain how oxygen and carbon dioxide move during respiration. External respiration is the exchange of gases in the lungs. Oxygen diffuses into the blood, and carbon dioxide diffuses out. Internal respiration happens in body tissues, where the gases move in the opposite directions. Two gas laws guide this process: Dalton's law of partial pressures and Henry's law. Dalton's law says the total pressure of a gas mixture equals the sum of the pressures of each gas acting alone. The...

external and internal respiration

Gas Exchange in Lungs and Tissues

Gas exchange in the lungs and body tissues moves oxygen into the blood and removes carbon dioxide. External respiration happens in the lungs, where inhaled oxygen enters the alveoli, the tiny air sacs that provide a large surface area for diffusion. Oxygen moves across the thin alveolar membrane into the pulmonary capillaries because its partial pressure is higher in the alveoli than in the blood. At the same time, carbon dioxide moves in the opposite direction and is later breathed out during...

oxygen transport in the blood

How Hemoglobin Loads and Releases Oxygen

Hemoglobin is the main molecule that carries oxygen in blood. It is found in red blood cells and has four polypeptide chains, each attached to an iron-containing heme group. This structure lets one hemoglobin molecule bind up to four oxygen molecules quickly and reversibly. When hemoglobin is fully loaded with oxygen, it is called oxyhemoglobin. When it has released oxygen, it is called reduced hemoglobin, or deoxyhemoglobin. As hemoglobin binds oxygen, its shape changes, which helps it pick...

carbon dioxide transport in the blood

How Blood Carries Carbon Dioxide

Carbon dioxide is carried in the blood from body tissues to the lungs. Cells make about 200 mL of CO2 each minute, and the lungs remove about the same amount. The blood moves this waste gas in three main forms. A small amount, about 7-10%, stays dissolved in the plasma. Just over 20% binds to hemoglobin and forms carbaminohemoglobin. In this case, CO2 attaches to the amino acids of globin, not to the heme part of hemoglobin. The rest, about 70%, is carried as bicarbonate ions, or HCO3-. CO2...

hypoxia

Hypoxia: Types and Carbon Monoxide Poisoning

Hypoxia is a medical condition in which body tissues do not get enough oxygen. It can cause a bluish color in the skin and mucosae, especially in fair-skinned people. This sign is often seen when hemoglobin (Hb) saturation drops below 75%. Hypoxia can happen for several different reasons. Anemic hypoxia occurs when there are too few red blood cells (RBCs) or when RBCs have abnormal or too little Hb. Ischemic hypoxia comes from poor blood circulation or blocked blood flow, so blood becomes...

neural control of respiration

Brainstem Centers That Control Breathing

Breathing is controlled by nerve centers in the brainstem. These respiratory centers send nerve signals to the muscles that move the lungs. The main centers are in the medulla oblongata and the pons.

chemical factors affecting respiration centers

chemical-factors-affecting-respiration-centers

How Blood Gases Control Breathing Rate

Blood gases and blood pH help control breathing rate and depth. Changes in carbon dioxide, oxygen, and hydrogen ion levels in arterial blood are detected by chemoreceptors, which are special sensors in the body. Central chemoreceptors are found throughout the brain stem, including the ventrolateral medulla. Peripheral chemoreceptors are located in the aortic arch and carotid arteries. Together, these sensors help the respiratory system respond to chemical changes in the blood. Carbon dioxide...

other factors affecting respiration centers

other-factors-affecting-respiration-centers

Respiratory Reflexes That Change Breathing

Breathing is controlled by the brainstem, but it can also be changed by the nervous system and by body signals. The cerebral motor cortex can override the medullary respiratory centers and send signals directly to the breathing muscles. This makes voluntary actions like holding your breath or taking deeper breaths possible. That control is limited. When carbon dioxide, or CO2, builds up in the blood to a critical level, the brainstem respiratory centers start breathing again. This is why a...

hyperpnea and hyperventilation

Breathing Changes in Exercise and Anxiety

Breathing changes in exercise and anxiety can look similar, but they do not have the same cause. Hyperventilation is a higher-than-normal rate and depth of breathing. It often happens during anxiety attacks and can push out more carbon dioxide than the body needs to remove. When too much carbon dioxide is lost, the blood develops hypocapnia, which means an unusually low level of carbon dioxide. Hypocapnia can narrow cerebral blood vessels and reduce blood flow to the brain. This may cause...

chronic obstructive pulmonary disease

COPD Signs, Causes, and Lung Damage

COPD is a lung condition that causes ongoing breathing problems. It leads to shortness of breath, cough, and sputum production because the airways become blocked and airflow is reduced. Smoking is the main risk factor for COPD, and more than 80% of patients have a history of it. People with COPD often develop worsening dyspnea, or labored breathing. They may also cough often and get repeated lung infections. Many patients with COPD can develop respiratory failure. This happens when...

other pulmonary disorders

Asthma, TB, Lung Cancer, and Sleep Apnea

Asthma, lung cancer, tuberculosis, and sleep apnea are major pulmonary disorders. They affect breathing in different ways. Some are chronic, some are infectious, and some can become life-threatening if not found and treated early. Asthma is marked by chronic airway inflammation and hypersensitivity. It can cause airway obstruction from bronchial spasms, mucosal edema, increased mucus secretion, or epithelial damage. Triggers vary and can include allergens or emotional upset. Treatment often...

key terms and concepts

Explore how the bronchi branch through the lungs, how bronchioles control airflow, and how cartilage, mucus, and alveoli support breathing in humans.

Bronchial Branching and Airflow Control | JoVE K12

anatomy and physiology

JoVE Core Anatomy and Physiology showcases the anatomical and physiological details of the human body in comprehensive, clear, and engaging video animations. This collection of lessons focuses on the structures, components, functions, and requirements of the human body. It is complemented by scientist-in-action videos that demonstrate the application of this knowledge in real-world medical and research settings.

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.43

Major Organs of the Digestive System

The human digestive system consists of two major parts: the gastrointestinal &#8212; GI &#8212; tract and the accessory organs.
The GI tract begins with ...

Peritoneum

The peritoneum is the body&#39;s largest serous membrane enveloping the abdominal cavity.
It has two portions &#8212; the parietal and visceral peritoneum ...

histology-of-the-gastrointestinal-gi-tract

Histology of the Gastrointestinal (GI) Tract

The gastrointestinal tract has four tissue layers.
The innermost layer, mucosa, is characterized as a mucous membrane. It consists of an epithelium, ...

Nerve Supply of the GI Tract

The gastrointestinal tract has its own intrinsic set of nerves forming the enteric nervous system or ENS,&#160; which is partly controlled by the ...

Regulation of the Digestive System

Along with the enteric nervous system, digestive activity is regulated by mechanical and chemical stimuli and hormones.
Various receptors located within ...

Blood Supply to the Digestive System

Splanchnic circulation refers to the network of blood vessels that supply and drain blood from the abdominal organs involved in digestion, including the ...

Oral Cavity

The oral cavity, or mouth, comprises the lips, cheeks, palate, and tongue.
The walls of the mouth are lined with thick, stratified squamous epithelium, ...

Tongue

The tongue, an accessory digestive organ, forms the floor of the oral cavity and extends into the oropharynx.
It is composed of two types of skeletal ...

Salivary Glands and Saliva

Saliva is composed of 97 to 99.5% water. The remaining proportion includes enzymes such as lipases and amylases, electrolytes, dissolved gasses, IgA, ...

Teeth

Teeth are accessory digestive organs that aid in physically breaking down food.
&#160;The gums, or gingivae, of both the mandible and maxilla hold the ...

Tooth Anatomy

The tooth has a crown and a root connected via a constricted area known as the neck.
The crown is visible above the gingivae and is protected by enamel.
...

Esophagus

The esophagus is a muscular conduit approximately 25 cm long that helps transport food from the mouth to the stomach.
It courses through the mediastinum ...

Deglutition

Deglutition, or swallowing, is a mechanism that transports food from the mouth to the stomach.
This process has three stages &#8212; the buccal, ...

Gross Anatomy of the Stomach

The stomach is a J-shaped organ connecting the esophagus to the duodenal end of the small intestine in the abdominal cavity.
The size and shape of the ...

Stomach Histology

The stomach wall consists of several layers, including the serosa, muscularis externa, submucosa, and mucosa.
The outermost layer, the serosa, is composed ...

Hormones Secreted by the Stomach

The specialized enteroendocrine cells of the gastric glands secrete most of the digestive hormones.
These cells, such as the G, D, and ...

Cephalic Phase of Digestion

Digestion has three overlapping phases &#8212; cephalic, gastric, and intestinal &#8212; based on the location of their control center.
The cephalic phase ...

Gastric Phase of Digestion

Local, neural and hormonal mechanisms trigger the gastric phase after food enters the stomach, lasting approximately 3-4 hours.
The incoming food bolus ...

Diseases of the Liver and Gallbladder

Prominent liver and gallbladder diseases include cirrhosis, hepatitis, non-alcoholic fatty liver disease or NAFLD, and gallstones.
Cirrhosis is a liver ...

Intestinal Phase of Digestion

After the gastric phase, the chyme from the stomach moves into the small intestine, gradually decreasing the stomach distention.
In contrast, the arrival ...

Pancreas

The pancreas is a pinkish-gray organ located behind the stomach. It extends from the duodenum to the spleen.
It can be divided into a broad head located ...

Mucosal Barrier of the Stomach

In the gastric glands, the parietal cells are involved in hydrochloric acid or HCl formation.
These cells first synthesize carbonic acid, which ...

Pancreatic Juice and Secretion

Pancreatic juice is a colorless liquid composed of water, salts, sodium bicarbonate, and enzymes secreted by the exocrine cells.
During digestion, chyme ...

Gastric Motility

Gastric motility is the coordinated movement of stomach muscles and secretions, which propels food and liquids through the stomach.
As the swallowed food ...

Small Intestine

The small intestine is a tubular structure extending from the pyloric sphincter of the stomach to the ileocecal valve of the large intestine.
This long, ...

Gastric Emptying

Gastric emptying is the gradual release of chyme from the stomach into the duodenum.
Stomach distention triggers the gastroenteric reflex, releasing ...

Histology of the Small Intestine

The histology of each part of the small intestine varies. The jejunum has the most prominent folds and villi, while the distal ileum has fewer folds but ...

Gross Anatomy of the Liver

The liver is the largest gland in the body, weighing approximately 1.4 kg in adults.
It is wedge-shaped and located more in the right hypochondriac and ...

mechanical-and-chemical-digestion-in-the-small-intestine

Mechanical and Chemical Digestion in the Small Intestine

The small intestine plays a crucial role in our digestive system, performing both mechanical and chemical digestion.
Mechanical digestion in the small ...

Liver Histology

The liver comprises several histological components, such as hepatocytes, bile canaliculi, and sinusoids.
Hepatocytes are specialized epithelial cells ...

Large Intestine

The large intestine is divided into three main regions: the cecum, colon, and rectum. Extending from the ileocecal valve to the anus, it frames the small ...

Bile

Bile is a yellow-green alkaline liquid secreted by the liver into the right and left hepatic ducts and then into the common hepatic duct. From here, it ...

Histology of the Large Intestine

The large intestine, a vital component of the gastrointestinal tract, is structured with four main layers: the mucosa, submucosa, muscularis, and serosa. ...

Gallbladder

The gallbladder is a muscular sac located in a shallow fossa on the inferior surface of the liver. It measures about 10 cm in length and is roughly the ...

Bacterial Flora of the Large

Intestine

The vast and varied community of bacteria colonizing the large intestine forms the gut microbiome.
Bacteria start residing in the gut at birth and ...

Liver Physiology

Liver functions primarily include bile production, metabolic regulation, and hematological functions.
During carbohydrate metabolism, the liver regulates ...

digestive-functions-of-the-large-intestine

Digestive Functions of the Large Intestine

The final stages of digestion occur in the large intestine when the cecum receives chyme, which has little nutritional value except for the indigestible ...

Absorption of Nutrients

During digestion in the small intestine, macromolecules&#8212; carbohydrates, proteins, and fats &#8212; are broken down into their simplest forms.
These ...

Feces Formation and Defecation

After spending 3 to 10 hours in the large intestine, chyme loses a lot of water and becomes feces, the final product of digestion. Feces consist of ...

Other Disorders of Digestive System

The gastrointestinal tract of the digestive system is susceptible to various disorders.
The incompetence of the lower esophageal sphincter results in the ...

Digestive System

Content elaboration: The digestive system consists of the gastrointestinal tract (alimentary canal) as well as various accessory organs including the teeth, tongue, salivary glands, liver, gallbladder and pancreas. The digestive system processes and supplies the molecules needed to sustain the living tissues within the body through the absorption of nutrients. Six major functions of the digestive system include secretion, ingestion, mechanical processing, enzymatic digestion, absorption and excretion. The lining of the digestive system protects surrounding tissues from the mechanical and enzymatic stresses of the digestive process. Processes of the digestive system include the mechanical and chemical breakdown of food into small molecules which are then absorbed by the digestive tract. Specific actions within the digestive system include mastication, peristalsis, segmentation and the release of hormones and enzymes necessary for digestion. The metabolic functions of the accessory organs play strategic roles in the breakdown of food products, the maintenance of glucose levels within the blood and the regulation of homeostasis in the body. Indigestible material is excreted as waste. Homeostatic imbalances are explored. These include, but are not limited to, conditions such as gallstones, heartburn, ulcers, dehydration, diarrhea, cirrhosis and cancers of the digestive system. Investigations are used to understand and explain the digestive system in a variety of inquiry and design scenarios that can incorporate evolutionary concepts, scientific reasoning, comparative analysis, communication skills and real-world applications.

Digestive System

Overview of Respiratory System

The respiratory system includes both upper and lower respiratory organs.
The upper respiratory organs consist of the nose and nasal cavity, paranasal ...

Respiratory System

Content elaboration: The respiratory system is comprised of the airways, lungs and diaphragm. The airways include the nasal and oral cavities, pharynx, larynx, trachea, bronchi, bronchioles and alveoli. The respiratory system transports and exchanges gases including oxygen and carbon dioxide. Processes involved in the respiratory system include respiration mechanics and gas exchange. Respiration mechanics is the process by which humans breathe and includes the movement of the diaphragm and pressure-volume relationships. Gas exchange refers to the diffusion of gas across the alveolar epithelium in the respiratory system and capillary endothelium of the cardiovascular system. Lung volumes and capacities can be measured using spirometry. Homeostatic imbalances are explored. These include, but are not limited to, asthma, chronic obstructive pulmonary disease (COPD), tuberculosis, cystic fibrosis and the effects of smoking and pollution. Investigations are used to understand and explain the respiratory system in a variety of inquiry and design scenarios that can incorporate evolutionary concepts, scientific reasoning, comparative analysis, communication skills and real-world applications.

Bronchial Branching and Airflow Control

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