Name: exhalation and lung pressure changes
Uploaded: 2024-09-12T13:22:46.000Z
Duration: 1 min 17 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

Pulmonary Cycle: Exhalation

يعتمد الزفير - عملية طرد الهواء - أثناء التنفس الهادئ لدى الأفراد الأصحاء على مرونة الرئتين بدلا من تقلص العضلات.
يؤدي ارتداد الألياف المرنة الممتدة أثناء الاستنشاق في المقام الأول إلى ارتداد الرئتين.
بالإضافة إلى ذلك ، فإن السحب الداخلي للتوتر السطحي الناتج عن طبقة السائل داخل الجنبة بين غشاء الجنب الحشوي والجداري يساهم في ارتداد الرئة.
عندما تتوقف العضلات المشاركة في الاستنشاق عن نشاطها ، يرتاح الحجاب الحاجز والوربية الخارجية ، مما يتسبب في صعود الحجاب الحاجز ونزول الأضلاع.
تقلل هذه الحركات من أبعاد التجويف الصدري ، وبالتالي تقلل من حجم الرئة.
أثناء الزفير ، يرتفع الضغط داخل الرئة إلى 1 مم زئبق فوق الضغط الجوي. وعندما يكون الضغط داخل الرئة أكبر من الضغط الجوي ، يتدفق الغاز من الرئتين.
على عكس هذا الزفير الهادئ ، يشمل الزفير القوي تقلص عضلات البطن والوربية. يجبر الحجاب الحاجز على الصعود من موضعه الطبيعي لطرد الهواء بالقوة.

التهوية الرئوية: الزفير

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فيما يتعلق بالتنفس البشري، فإن عملية إخراج الهواء، المعروفة بالزفير، تعمل على مبدأ تدرجات الضغط. أثناء الزفير، يتجاوز الضغط داخل الرئتين ضغط الغلاف الجوي المحيط. في الظروف العادية، يتضمن التنفس الهادئ زفيرًا سلبيًا وخاليًا من الانقباضات العضلية. وذلك لأن عملية الزفير مدفوعة بالارتطام المرن الطبيعي للرئتين وجدار الصدر، وكلاهما لديه ميل متأصل للعودة إلى وضعهما الأصلي بعد التمدد.

مع توقف العضلات المشاركة في الشهيق عن نشاطها، يسترخي الحجاب الحاجز والعضلات بين الأضلاع الخارجية. وهذا يتسبب في صعود الحجاب الحاجز ونزول الأضلاع. تعمل هذه الحركات على تقليل أبعاد التجويف الصدري، مما يقلل من حجم الرئة ويزيد من ضغط الحويصلات الهوائية إلى حوالي 762 ملم زئبق. يجبر هذا الفرق في الضغط تدفق الهواء من الرئتين (ضغط أعلى) إلى الغلاف الجوي (ضغط أقل). لا يتطلب الزفير سوى بذل جهد نشط أثناء بذل مجهود بدني شديد، مثل ممارسة الرياضة أو عند العزف على آلة النفخ. في مثل هذه الأوقات، تنخرط العضلات المشاركة في الزفير - العضلات البطنية والعضلات الوربية الداخلية - مما يسبب الضغط داخل منطقة البطن والصدر. يضغط تقلص عضلات البطن على الأعضاء البطنية، مما يدفع الحجاب الحاجز إلى الأعلى، بينما تسحب العضلات الوربية الداخلية الأضلاع إلى الأسفل من خلال امتدادها السفلي والخلفي بين الأضلاع المجاورة. على الرغم من أن الضغط داخل الجنبة يظل دائمًا أقل من الضغط داخل الحويصلات الهوائية، إلا أنه يمكن أن يتجاوز الضغط الجوي مؤقتًا أثناء الزفير القوي، مثل السعال.

بعض الحالات السريرية المرتبطة بالتهوية الرئوية

1. متلازمة الضائقة التنفسية عند حديثي الولادة

تؤثر متلازمة الضائقة التنفسية عند حديثي الولادة، أو مرض الغشاء الزجاجي، في المقام الأول على الأطفال الخدج. تنشأ هذه الحالة بسبب عدم كفاية إنتاج المادة الخافضة للتوتر السطحي في الرئتين، وهي مادة تساعد في إبقاء الحويصلات الهوائية مفتوحة. بدون وجود مادة فعالة سطحية كافية، تنهار الحويصلات الهوائية أثناء الزفير، مما يجعل التنفس أكثر صعوبة بالنسبة للرضيع.

تتضمن أعراض متلازمة الضائقة التنفسية التنفس السريع والضحل، وتوسع فتحتي الأنف، وأصوات الشخير، ولون مزرق للجلد (زرقة). غالبًا ما يتضمن العلاج توفير الأكسجين الإضافي وإعطاء علاج بديل للمادة الفعالة السطحية لتحسين وظائف الرئة. يتعافى معظم الأطفال من متلازمة الضائقة التنفسية في غضون بضعة أيام إلى أسابيع مع التدخل الطبي المناسب.

2. انخماص الرئة

انخماص الرئة هو انهيار جزئي لجزء من الرئة. يمكن أن تحدث هذه الحالة لأسباب مختلفة، مثل انسداد مجرى الهواء، أو جروح الطعنات أو الطلقات النارية في الصدر، أو الفتح الجراحي للصدر، أو ضعف أنسجة الرئة. تشمل الأسباب الشائعة سدادات المخاط، والأورام، والأجسام الغريبة، والمضاعفات بعد الجراحة.

تعتمد أعراض انخماص الرئة على مدى انهيار الرئة وقد تشمل ألم الصدر، وضيق التنفس، وزيادة معدل ضربات القلب، والسعال. تتراوح خيارات العلاج من تمارين التنفس العميق وتقنيات السعال إلى موسعات الشعب الهوائية أو الجراحة في الحالات الشديدة.

3. التهاب الشعب الهوائية

التهاب الشعب الهوائية هو التهاب في الشعب الهوائية. يمكن أن تكون الحالة حادة أو مزمنة، حيث تعد العدوى الفيروسية السبب الأكثر شيوعًا لالتهاب الشعب الهوائية الحاد. من ناحية أخرى، غالبًا ما يرتبط التهاب الشعب الهوائية المزمن بالتعرض الطويل الأمد لمهيجات مثل دخان التبغ وتلوث الهواء.

قد تشمل أعراض التهاب الشعب الهوائية السعال المستمر وإنتاج المخاط وعدم الراحة في الصدر والصفير. يتضمن العلاج عادةً الراحة والبقاء رطبًا والأكسجين وموسعات الشعب الهوائية ومعالجة السبب الأساسي. إذا كانت هناك عدوى بكتيرية، فقد يتم وصف المضادات الحيوية.
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يعتمد الزفير - عملية طرد الهواء - أثناء التنفس الهادئ لدى الأفراد الأصحاء على مرونة الرئتين بدلا من ...

Education

JoVE Core

Anatomy and Physiology

التشريح وعلم وظائف الأعضاء

Unit 1

الوحدة الأولى

The Respiratory System

الجهاز التنفسي

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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 downward. These changes make the thoracic cavity smaller and reduce lung volume. As a result, alveolar pressure rises to about 762 mm Hg, and air flows out of the lungs into the lower-pressure atmosphere.

Active exhalation happens during exercise or when playing a wind instrument. In these cases, the abdominal muscles and internal intercostals contract. Abdominal muscle contraction compresses the abdominal organs and pushes the diaphragm upward. The internal intercostals pull the ribs downward because of their inferior and posterior position between adjacent ribs.

The pressure in the pleural space remains lower than the pressure inside the alveoli, but it can briefly rise above atmospheric pressure during forceful exhalation, such as coughing. The same pressure changes that help air leave the lungs can also relate to lung problems. Neonatal respiratory distress syndrome, atelectasis, and bronchitis are all conditions connected to pulmonary ventilation.

Neonatal respiratory distress syndrome, also called hyaline membrane disease, mainly affects premature infants. It happens when the lungs do not produce enough surfactant, a substance that helps keep alveoli open. Without enough surfactant, alveoli can collapse during exhalation, which makes breathing difficult. Common signs include rapid shallow breathing, nostril flaring, grunting, and cyanosis, or a bluish skin color. Treatment often includes supplemental oxygen and surfactant replacement therapy, and many infants recover within days to weeks.

Atelectasis is a partial collapse of part of a lung. It can result from blocked airways, stab or gunshot wounds, surgical opening of the chest, or weakened lung tissue. Common causes include mucus plugs, tumors, foreign objects, and post-surgical complications. Symptoms may include chest pain, shortness of breath, a faster heart rate, and coughing. Treatment can include deep breathing exercises, coughing techniques, bronchodilators, or surgery in severe cases.

Bronchitis is inflammation of the bronchial tubes. Acute bronchitis is most often caused by viral infections. Chronic bronchitis is often linked to long-term exposure to irritants such as tobacco smoke and air pollution. Symptoms can include a persistent cough, mucus production, chest discomfort, and wheezing. Treatment usually includes rest, hydration, oxygen, bronchodilators, and care for the underlying cause. If a bacterial infection is present, antibiotics may be used.

Exhalation and Lung Pressure Changes

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

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...

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 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

Learn how exhalation works through pressure changes, when breathing becomes active, and how conditions like RDS, atelectasis, and bronchitis affect ventilation.

Exhalation and Lung Pressure Changes | 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.

Alabama Course of Study Science

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From Molecules to Organisms: Structures and Processes

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Florida Department of Education

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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

Exhalation and Lung Pressure Changes

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