Physiology of the Respiratory System - Medicine Paper Example

Also called the voice box, is made up of cartilage that gives it structure to connect the trachea and laryngopharynx. It consists of epiglottis that covers the larynx during swallowing and the thyroid cartilage which also commonly referred to as Adam's apple very prominent on adult males. The thyroid protects the vocal folds by holding the interior of the larynx. The cricoid cartilage is ring shape found in below the thyroid cartilage helps to keep the larynx open. Inside the larynx are vocal folds that allow sound production to occur through the vibration of the mucous membrane.

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Trachea

Also known as the windpipe, is a c-shaped tube made of thick hyaline cartilage rings with a pseudostratified ciliated epithelium lining. It connects the bronchi to the larynx allowing air into the thorax. The trachea's primary function is to provide passage of air into and out of the lungs, and it traps contaminants by the mucus produced by the epithelium lining. Cilia moves the mucus up the surface of the trachea towards the pharynx so as to get rid of it.

Bronchi and Bronchioles

The primary bronchi consist of both the left and the right branches of the trachea splits. They both branch into secondary bronchi, two in the left lung and three in the right lung lobes. They branch into tertiary bronchi and then into many bronchioles spreading into the entire lungs. The bronchioles supply air to the alveoli. The bronchioles do not have cartilage but smooth muscles allowing them to be flexible and contractile so as to help regulate air flow into the lungs.

Lungs

These are the spongy pair of organs located in the thoracic cavity next to the heart above the diaphragm. Surround the lungs are pleural membranes that provide room for expansion during inhalation. The left lobe is smaller than the right portion since the heart points into the left side. Inside the lungs are spongy tissues hosting many capillaries in a tiny sac called the alveoli. Thin epithelium line the sacs allowing for air exchange to take place.

Respiratory muscles

These are muscles surrounding the lungs that are responsible for inhalation and exhalation of air. The diaphragm is a thin sheet-like collection of skeletal muscles forming the thorax and is the primary muscle controlling the respiratory cycle through contraction and relaxation. Intercostal muscles are found in between the ribs also assist the diaphragm with compressing and expansion of the lungs. They consist of the external and internal intercostal muscle. The external intercostal muscles contract as the internal relax expanding the thoracic cavity causing inhalation. The internal intercostal muscles collapse the libs compressing the thoracic cavity causing exhalation.

Physiology of the Respiratory System

Pulmonary Ventilation

It is the process of facilitating gas exchange through moving air into the lungs and out. The system works by using both contraction and negative pressure to accomplish pulmonary ventilation. When the lungs are at rest, the pleural membrane closes the lungs maintaining a slightly higher pressure than the environment causing a negative pressure gradient between the external atmosphere and the alveoli. Air flows into the lungs to equalize the lung pressure to the atmospheric pressure. More air flows into the lungs by the contraction of the diaphragm and the external intercostal muscles resulting in an increase in volume. During exhalation, the external intercostal muscle and the diaphragm relax as the intercostal muscles contract to reduce the volume of the thoracic cavity. The processes reverse the pressure gradient forcing air out to the environment.

External Respiration

It takes place when air from the atmosphere fills the alveoli. The air has a higher concentration of oxygen and a lower concentration of carbon dioxide than that in the capillaries. The difference in respective pressure gradients causes exchange of gasses through the simple epithelium lining resulting to external respiration. The oxygen is transported to the tissues while the carbon dioxide gets released into the atmosphere.

Internal Respiration

It refers to the exchange of respiratory gasses from the blood capillaries to the body tissues. Diffusion of these gasses occurs due to the partial pressure difference of the two. The capillaries have a higher partial pressure of oxygen and a lower partial pressure carbon dioxide compared to the tissues.

Transportation of Gases

Oxygen and carbon dioxide are the primary respiratory gasses that are transported by blood. Most of the gasses bind with the blood, but some get dissolved in the blood plasma. The red blood cells responsible for carrying the gasses do so by the help of hemoglobin molecules. Hemoglobin can take small amounts of carbon dioxide, but a majority gets transported as bicarbonate ion by blood plasma. The enzyme carbonic anhydrase facilitates the reaction of water and carbon to form carbonic acid that dissociates into a bicarbonate ion and hydrogen ion if the carbon dioxide is high in the tissues. When the pressure is lower in the lungs, the process reverses.

Homeostatic Control of Respiration

Eupnea is the usual depth and quiet breathing that the body maintains during resting when the oxygen demand is healthy. It refers to the unlabored ventilation as expiration involves only the elastic recoil of the lungs. The neural output to the external intercostal muscles and diaphragm is very regular and rhythmic.

The Gastrointestinal Tract

The system is a hollow muscular pipe running from the oral cavity where food is ingested into the body, through the pharynx, esophagus, stomach, intestines, rectum and finally to the anus where waste byproducts of digestion process get expelled. Other tertiary organs help by secreting enzymes that assist in the breaking down of food to nutrients. The muscular walls move the food through the system by peristaltic movement. Primarily the gastrointestinal tract extracts nutrients from food and makes them available for the body so as to produce energy.

Primary structure

The epithelium cells line the muscular tube of the gastrointestinal tract although each section has its specific functions. The tubular wall has two different layers recorded below.

Mucosa

Specialized epithelial cells are the innermost layer of the tract and draw support from the lamina propria which are a layer of connective tissue. The lamina propria has a lymphoid tissue, nerves, blood vessels and support for mucosa. The epithelium can be simple or stratified depending on function. Stratified squamous epithelium cells cover the mouth and the esophagus so as to survive wear and tear off food during chewing and swallowing. Granular epithelium covers the stomach and intestines to support absorption and secretion. The lining is scrapped and replaced regularly. Smooth muscles called the muscularis mucosa are found at the bottom of the lamina propriaa and can change the shape of the lumen by contracting

Submucosa

It consists of fatty, fibrous connective tissue with nerves and larger blood vessels surround the muscularis. Submucosal nerve plexus supply the mucosa and the submucosa.

Muscularis externa

These are smooth muscle having an outer longitudinal layer and the inner circular layer of muscle fibers. In between, they are the myenteric or Auerbach plexus. The nerves control the contraction of these muscles making it possible to break down food within the lumen mechanically.

Serosa/mesentery

They are the outer layer consisting of fat and a layer of mesothelium which is a type of epithelial cells.

Individual components of the gastrointestinal system

Oral cavity

The mouth takes in food, and it is lined by keratin-covered by stratified squamous mucosa making it resistant to abrasion. Examples of such parts are the tongue and mouth roof. The teeth perform the mechanical breakdown of food by chopping and chewing action. The tongue is a strong muscular organ that manipulates food and is also a sensory organ for taste and temperature by the help of the papillae. The mouth has serum amylase, which is an enzyme that starts the digestion process. Some of the water and glucose is absorbed across the mucosa and finally the bolus of passed to the esophagus through the pharynx by swallowing.

Salivary glands

The oral cavity has three salivary glands. Each gland has many acini which secrete into specialized ducts and separate into different lobes. During tasting or smelling, salivation occurs due to nerve signals that prepare the mouth for the incoming food. The content of each salivary gland is not similar in composition.

The parotid gland located below the zyomatic arch and the mandible, are large irregular in shape gland that secretes almost a quarter of the saliva. The secretions are rich in proteins and immunoglobins that assist in fighting microorganism. Breakdown of carbohydrates begins here due to the secretion of a-amylase proteins.

The submandibular glands found in the mouth floor are responsible for the secretion of most saliva in the mouth which is viscous. The secretions are rich in mucin glucose that further lubricates food.

The sublingual gland secrets about five percent of the saliva. These small glands located on the floor of the mouth and a thin layer of tissue covers it. The saliva produced is the most viscous due to the...