16.3: Blood Vessel and Respiratory System (2023)

Respiratory system

Inhale and hold your breath. Wait a few seconds and then release it. People, when not exercising, breathe on average about 15 times per minute. This equates to approximately 900 breaths per hour or 21,600 breaths per day. With each inhalation, air fills the lungs, and with each exhalation, it comes back out. This air does more than inflate and deflate the lungs in the chest cavity. Air contains oxygen that passes through lung tissue, enters the bloodstream, and travels to organs and tissues. There, oxygen is exchanged for carbon dioxide, which is a cellular waste material. Carbon dioxide leaves the cells, enters the bloodstream, travels back to the lungs, and is expelled from the body during exhalation.

Breathing is both a voluntary and an involuntary event. The frequency with which one inhales and the amount of air one inhales or exhales is regulated by the respiratory center of the brain in response to signals it receives about the carbon dioxide content in the blood. However, it is possible to override this automatic regulation for activities such as speaking, singing and swimming underwater.

During inhalation, the diaphragm descends, creating a negative pressure around the lungs and the lungs begin to inflate, drawing air out of the body. Air enters the body through the nasal cavity located directly inside the nose (image \(\PageIndex{1}\)). As the air passes through the nasal cavity, it warms to body temperature and becomes moist with moisture from the mucous membrane. These procedures help balance the air with the body's condition, reducing the damage that cold, dry air can cause. Airborne particles are removed in the nasal passages by hairs, mucus, and villi. Air is also chemically absorbed by the sense of smell.

From the nasal cavity, air passes through the pharynx (throat) and larynx (voice box) on its way to the trachea (image \(\PageIndex{1}\)). The main function of the trachea is to channel inhaled air into the lungs and exhaled air out of the body. The human trachea is a cylinder, approximately 25–30 cm (9.8–11.8 in) long, located in front of the esophagus and extending from the pharynx through the chest cavity to the lungs. It is built from incomplete rings of cartilage and smooth muscle. Cartilage provides strength and support to the windpipe to keep the passageway open. The trachea is lined with cells that have cilia and secrete mucus. The mucus traps the inhaled particles, and the cilia move the particles toward the pharynx.

The final part of the trachea divides into two bronchi that enter the right and left lung. Air enters the lungs through the primary bronchi. The primary bronchus divides, producing smaller and smaller bronchi until the passages are less than 1 mm (0.03 in) in diameter, when they are called bronchioles because they rupture and spread through the lungs. Like the trachea, the bronchi and bronchioles are made up of cartilage and smooth muscle. The bronchi are innervated by nerves from the sympathetic and parasympathetic nervous systems that control muscle contraction (parasympathetic) or relaxation (sympathetic) in the bronchi and bronchioles, based on signals from the nervous system. Terminal bronchioles are respiratory bronchioles. The alveolar ducts join at the end of each respiratory bronchiole. At the end of each duct are alveolar sacs, each containing 20 to 30 alveoli. Gas exchange takes place only in the alveoli. The alveoli have thin walls and look like small bubbles inside sacs. The alveoli are in direct contact with the capillaries of the blood vessel system. This close contact ensures that oxygen will diffuse from the alveoli into the blood. Also, carbon dioxide will diffuse from the blood into the alveoli to be exhaled. The anatomical arrangement of capillaries and alveoli emphasizes the structural and functional connection of the respiratory and circulatory systems. Estimates of the alveolar surface area in the lungs vary by about 100 m². This large area is about half the size of a tennis court. This large surface area, combined with the thin-walled nature of alveolar cells, allows gases to diffuse easily into the cells.

THE ART CONNECTION

Which of the following statements about the human respiratory system is false?

See Also

Which of the following maintains tracheal patency?How does feedback inhibition affect enzyme activity?Unusual intravenous catheter sites in small animals

1. When we inhale, the air travels from the pharynx to the trachea.
2. The bronchioles branch into bronchi.
3. The alveolar ducts are connected to the alveolar sacs.
4. Gas exchange between the lungs and the blood takes place in the alveoli.

Sistema cardiovascular

The circulatory system is a network of blood vessels - arteries, veins and capillaries - and a pump, the heart. In all vertebrates, this is a closed-loop system, in which blood is largely separated from the body's second extracellular fluid compartment, the interstitium, the fluid that bathes the cells. Blood circulates within the blood vessels and circulates unidirectionally from the heart around one of the two circulatory pathways and then back to the heart again. this is a closed circulatory system. Open circulatory systems are found in invertebrates in which the circulatory fluid directly bathes the internal organs, although it may be powered by a cardiac pump.

Heart

The heart is a complex muscle made up of two pumps: one that pumps blood through the pulmonary circulation to the lungs, and another that pumps blood through the systemic circulation to the rest of the body's tissues (and to the heart itself).

The heart is asymmetric, with the left side larger than the right, which correlates with the different sizes of the pulmonary and systemic circuits (Figure \(\PageIndex{2}\)). In humans, the heart is about the size of a clenched fist. divided into four chambers: two atria and two ventricles. On the right side are the atrium and ventricle, and on the left side are the atrium and ventricle. The right atrium receives deoxygenated blood from the systemic circulation through the main veins: the superior vena cava, which drains blood from the head and the veins branching from the arms, and the inferior vena cava, which drains blood from the veins They come from the lower organs and the legs. This deoxygenated blood then passes into the right ventricle through the tricuspid valve, preventing backflow of blood. After filling, the right ventricle contracts and pumps blood to the lungs for reoxygenation. The left atrium receives oxygen-rich blood from the lungs. This blood passes through the bicuspid valve into the left ventricle, where the blood is pumped into the aorta. The aorta is the main artery in the body, carrying oxygen-enriched blood to the organs and muscles of the body. This pumping pattern is called double circulation and is found in all mammals. (Image \(\PageIndex{2}\)).

THE ART CONNECTION

Which of the following statements about the circulatory system is false?

1. The blood in the pulmonary vein is deoxygenated.
2. The blood in the inferior vena cava is deoxygenated.
3. The blood in the pulmonary artery is deoxygenated.
4. The blood in the aorta is oxygenated.

Cardiac cycle

The main purpose of the heart is to pump blood throughout the body. it does so in a repetitive sequence called the cardiac cycle. The cardiac cycle is the flow of blood through the heart coordinated by electrochemical signals that cause the heart muscle to contract and relax. In each cardiac cycle, a series of contractions push blood out, pumping it throughout the body. This is followed by the relaxation phase, in which the heart fills with blood. These two phases are called contraction (contraction) and dilation (relaxation) respectively (image \(\PageIndex{3}\)). The signal for the contraction begins at a site on the outside of the right atrium. An electrochemical signal travels from there to the atria and causes them to contract. Contraction of the atria forces blood through the valves into the ventricles. The closure of these valves caused by the contraction of the ventricles produces a "lumping" sound. Until now, the signal passed under the walls of the heart, through the point between the right atrium and the right ventricle. The signal then causes the ventricles to contract. The ventricles contract and push blood into the aorta and pulmonary arteries. Closure of the valves in these arteries caused by blood returning to the heart during ventricular relaxation produces a monosyllabic "dub" sound.

The pumping of the heart is a function of the heart muscle cells or cardiomyocytes that make up heart muscle. Cardiomyocytes are special muscle cells that are striated like skeletal muscles, but pump rhythmically and involuntarily like smooth muscles. neighboring cells are connected by intercalated discs found only in heart muscle. These connections allow the electrical signal to travel directly to neighboring muscle cells.

Electrical impulses in the heart produce electrical currents that flow through the body and can be measured on the skin using electrodes. This information can be viewed as an electrocardiogram (ECG) as a recording of the electrical impulses from the heart muscle.

Blood vessels

Blood from the heart is carried throughout the body through a complex network of blood vessels (Figure \(\PageIndex{4}\)). Arteries carry blood away from the heart. The main artery of the systemic circulation is the aorta. it branches into major arteries that carry blood to various extremities and organs. The aorta and the arteries close to the heart have thick but elastic walls that respond to and smooth out the pressure differences caused by the heartbeat. Arteries farther from the heart have more muscle tissue in their walls that can constrict and affect blood flow. The main arteries divide into smaller arteries and then into smaller vessels called arterioles to go deeper into the muscles and organs of the body.

The arterioles separate into capillary layers. The capillary layers contain a large number of 10 to 100 capillaries that branch between the cells of the body. Capillaries are narrow-diameter tubes that can contain individual red blood cells and are the sites for the exchange of nutrients, wastes, and oxygen with tissues at the cellular level. Fluid also leaks from the blood into the interstitial space of the capillaries. The capillaries again converge into venules that join smaller veins that eventually join larger veins. Veins are blood vessels that return blood containing carbon dioxide to the heart. Veins do not have as thick walls as arteries because the pressure is lower, and they have valves along them that prevent blood from flowing back from the heart. The large veins drain blood from the same organs and extremities that supply the main arteries.

Unit Summary

Animal respiratory systems are designed to facilitate gas exchange. In mammals, the air is heated and humid in the nasal cavity. The air then travels down the pharynx and larynx, through the trachea, and into the lungs. In the lungs, air passes through the branching bronchi, reaching the respiratory bronchioles. The respiratory bronchioles open into the alveolar ducts, alveolar sacs, and alveoli. Because there are so many alveoli and alveolar sacs in the lungs, the surface area for gas exchange is very large.

The mammalian circulatory system is a closed system with a double circulation that passes through the lungs and the body. It consists of a network of blood vessels that circulate due to the pressure differences created by the heart.

The heart contains two pumps that move blood through the pulmonary and systemic circulation. On the right side are the atrium and ventricle, and on the left side are the atrium and ventricle. The pumping of the heart is a function of cardiomyocytes, characteristic muscle cells that are striated like skeletal muscle but pump rhythmically and involuntarily like smooth muscle. The contraction signal begins in the wall of the right atrium. An electrochemical signal causes the two atria to contract simultaneously. the signal then causes the ventricles to contract. Blood from the heart is carried throughout the body through a complex network of blood vessels. arteries take blood away from the heart and veins return it to the heart.

artistic connections

Figure \(\PageIndex{1}\): Which of the following statements about the human respiratory system is false?

A. When we inhale, air travels from the pharynx to the trachea.
B. Bronchioles branch into bronchi.
C. The alveolar ducts are connected to the alveolar sacs.
D. Gas exchange between the lungs and the blood takes place in the alveoli.

Answer

y

Figure \(\PageIndex{2}\): Which of the following statements about the circulatory system is false?

A. The blood in the pulmonary vein is deoxygenated.
B. The blood in the inferior vena cava is deoxygenated.
C. The blood in the pulmonary artery is deoxygenated.
D. The blood in the aorta is oxygenated.

Answer

ONE

Contributions and literature

• Samantha Fowler (Clayton State University), Rebecca Roush (Sandhills Community College), James Wise (Hampton University). Izvorni sadržaj s OpenStaxa (CC BY 4.0; besplatan pristup nahttps://cnx.org/contents/b3c1e1d2-83...4-e119a8aafbdd).