They can all happen simultaneously and share the same in Q: Describe the similarities between pain and the other somatic sensations? A: The somatic sensation is referred to as the body sensation related to touch, pain, temperature, and Q: What are the target tissues and effects of calcitonin and parathyroid hormone? A: Calcitonin is a hormone produced by the parafollicular cells C-cells present in the thyroid.
Q: describe the components and physical properties ofblood;. A: The different components of blood can be enlisted as Plasma : it is the liquid component of the blo Q: describe in general terms how blood is produced.
A: One of the most abundant and well-distributed tissues in our body is the connective tissue. It provi Q: Which of these bones does not contain a paranasal sinus? A: Paranasal sinus is referred to as the air-filled spaces present around the nasal cavity. There are f Q: A muscle located on the chest wall is the a. A: Muscle referred to as soft body tissue principally responsible for causing the movement in the body Q: Which of these is not a suprahyoid muscle?
A: Suprahyoid muscle is a group of muscle present in the neck superior to the hyoid bone. It is involve A: Anatomical terms of bone.
Trauma is a significant component in the aetiology of xiphoid syndrome. Q: My answer is incorrect, i want to use this to study can you please provide me with the correct answe A: A capillary is a microscopic tube like structure or channel that delivers blood to the tissues via p Q: List several abnormal urine components, and name the condition characterized by the presence of dete A: Urine, a typically sterile liquid by-product of the body, is secreted by the kidneys through a proce Q: What structures in the embryo are derived from the somites?
A: During early embryonic development a single layer hollow sphere of cells known as blastula converted Q: ventricular relaxation immediately follows. A: Heart Heart is a mesodermal origin. It is located in the thoracic chest cavity under the rib cage Q: Which of the following rows correctly identifies the endocrine disorder, the level of the hormones i A: The hormone imbalance is a serious issue that threatens the homeostasis of the human body due to its Q: List the vessels through which blood flows from the aorta to the myocardium and back to the right at A: The heart is a hollow muscular organ that pumps blood through the circulatory system by dilation and Q: Describe the flow of blood from the heart through allmajor parts of the body.
A: Right Side Blood enters the heart through two large veins, the inferior and superior vena cava, empt Q: What type of cellular process is most likely the mechanism employed by osteoblasts to release bone m A: Osteoblasts are the bone cells that function to synthesize the skeletal system's component called th A: Erythrocytes or Red blood cells undergo a continuous breakdown known as hemolysis.
Erythrocytes circ Q: We are focusing mainly on synovial joints, because this is the main type of joint that allows you to A: Our body has many bones which are held together at joints and synovial joint is the most common Q: describe the typical anatomy of a gland;. A: A gland is an organ that generates and produces chemical compounds that in the body serve a particul Q: The short-term response to stress occurs faster than the long-term response to stress because Selec A: The action potential is an electrochemical process carried out by neurons in order to transfer signa Q: Match the chromosome disorder to its descriptionin the key.
Turner syndrome a. A: Chromosomal disease, any condition of any of the body's structures marked by abnormalities or defect Q: Compare eccrine sweat gland density on the forehead, forearm, palm, and anterior leg. In addition, many veins, particularly in the lower limbs, contain valves formed by sections of thickened endothelium that are reinforced with connective tissue, extending into the lumen. Under the microscope, the lumen and the entire tunica intima of a vein will appear smooth, whereas those of an artery will normally appear wavy because of the partial constriction of the smooth muscle in the tunica media, the next layer of blood vessel walls.
The tunica media is the substantial middle layer of the vessel wall see Figure 2. It is generally the thickest layer in arteries, and it is much thicker in arteries than it is in veins.
The tunica media consists of layers of smooth muscle supported by connective tissue that is primarily made up of elastic fibers, most of which are arranged in circular sheets. Toward the outer portion of the tunic, there are also layers of longitudinal muscle. Contraction and relaxation of the circular muscles decrease and increase the diameter of the vessel lumen, respectively. Specifically in arteries, vasoconstriction decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure.
Similarly, vasodilation increases blood flow as the smooth muscle relaxes, allowing the lumen to widen and blood pressure to drop. These are generally all sympathetic fibers, although some trigger vasodilation and others induce vasoconstriction, depending upon the nature of the neurotransmitter and receptors located on the target cell.
Parasympathetic stimulation does trigger vasodilation as well as erection during sexual arousal in the external genitalia of both sexes. Nervous control over vessels tends to be more generalized than the specific targeting of individual blood vessels. Local controls, discussed later, account for this phenomenon.
Seek additional content for more information on these dynamic aspects of the autonomic nervous system. Hormones and local chemicals also control blood vessels. Together, these neural and chemical mechanisms reduce or increase blood flow in response to changing body conditions, from exercise to hydration. Regulation of both blood flow and blood pressure is discussed in detail later in this chapter. The smooth muscle layers of the tunica media are supported by a framework of collagenous fibers that also binds the tunica media to the inner and outer tunics.
Along with the collagenous fibers are large numbers of elastic fibers that appear as wavy lines in prepared slides. Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane also called the external elastic lamina , which also appears wavy in slides. This structure is not usually seen in smaller arteries, nor is it seen in veins.
The outer tunic, the tunica externa also called the tunica adventitia , is a substantial sheath of connective tissue composed primarily of collagenous fibers. Some bands of elastic fibers are found here as well. The tunica externa in veins also contains groups of smooth muscle fibers. This is normally the thickest tunic in veins and may be thicker than the tunica media in some larger arteries.
The outer layers of the tunica externa are not distinct but rather blend with the surrounding connective tissue outside the vessel, helping to hold the vessel in relative position.
If you are able to palpate some of the superficial veins on your upper limbs and try to move them, you will find that the tunica externa prevents this. If the tunica externa did not hold the vessel in place, any movement would likely result in disruption of blood flow. An artery is a blood vessel that conducts blood away from the heart.
All arteries have relatively thick walls that can withstand the high pressure of blood ejected from the heart. However, those close to the heart have the thickest walls, containing a high percentage of elastic fibers in all three of their tunics.
This type of artery is known as an elastic artery see Figure 3. Vessels larger than 10 mm in diameter are typically elastic. Their abundant elastic fibers allow them to expand, as blood pumped from the ventricles passes through them, and then to recoil after the surge has passed.
If artery walls were rigid and unable to expand and recoil, their resistance to blood flow would greatly increase and blood pressure would rise to even higher levels, which would in turn require the heart to pump harder to increase the volume of blood expelled by each pump the stroke volume and maintain adequate pressure and flow.
Artery walls would have to become even thicker in response to this increased pressure. The elastic recoil of the vascular wall helps to maintain the pressure gradient that drives the blood through the arterial system.
An elastic artery is also known as a conducting artery, because the large diameter of the lumen enables it to accept a large volume of blood from the heart and conduct it to smaller branches. Figure 3. Comparison of the walls of an elastic artery, a muscular artery, and an arteriole is shown. In terms of scale, the diameter of an arteriole is measured in micrometers compared to millimeters for elastic and muscular arteries.
The artery at this point is described as a muscular artery. The diameter of muscular arteries typically ranges from 0. Their thick tunica media allows muscular arteries to play a leading role in vasoconstriction. In contrast, their decreased quantity of elastic fibers limits their ability to expand. Fortunately, because the blood pressure has eased by the time it reaches these more distant vessels, elasticity has become less important. Rather, there is a gradual transition as the vascular tree repeatedly branches.
In turn, muscular arteries branch to distribute blood to the vast network of arterioles. For this reason, a muscular artery is also known as a distributing artery. An arteriole is a very small artery that leads to a capillary.
Arterioles have the same three tunics as the larger vessels, but the thickness of each is greatly diminished. The critical endothelial lining of the tunica intima is intact. The tunica media is restricted to one or two smooth muscle cell layers in thickness. The tunica externa remains but is very thin see Figure 3. With a lumen averaging 30 micrometers or less in diameter, arterioles are critical in slowing down—or resisting—blood flow and, thus, causing a substantial drop in blood pressure.
Because of this, you may see them referred to as resistance vessels. The muscle fibers in arterioles are normally slightly contracted, causing arterioles to maintain a consistent muscle tone—in this case referred to as vascular tone—in a similar manner to the muscular tone of skeletal muscle. In reality, all blood vessels exhibit vascular tone due to the partial contraction of smooth muscle. The importance of the arterioles is that they will be the primary site of both resistance and regulation of blood pressure.
The precise diameter of the lumen of an arteriole at any given moment is determined by neural and chemical controls, and vasoconstriction and vasodilation in the arterioles are the primary mechanisms for distribution of blood flow.
A capillary is a microscopic channel that supplies blood to the tissues themselves, a process called perfusion. Exchange of gases and other substances occurs in the capillaries between the blood and the surrounding cells and their tissue fluid interstitial fluid. The diameter of a capillary lumen ranges from 5—10 micrometers; the smallest are just barely wide enough for an erythrocyte to squeeze through. Flow through capillaries is often described as microcirculation. The wall of a capillary is different from other vessels, as it consists only of an endothelial layer surrounded by a basement membrane with occasional smooth muscle fibers.
There is some variation in wall structure: In a large capillary, several endothelial cells bordering each other may line the lumen; in a small capillary, there may be only a single cell layer that wraps around to contact itself.
For capillaries to function, their walls must be leaky, allowing substances to pass through. The most common type of capillary, the continuous capillary , is found in almost all vascularized tissues. Continuous capillaries are characterized by a complete endothelial lining with tight junctions between endothelial cells. Although a tight junction is usually impermeable and only allows for the passage of water and ions, they are often incomplete in capillaries, leaving intercellular clefts that allow for exchange of water and other very small molecules between the blood plasma and the interstitial fluid.
Substances that can pass between cells include metabolic products, such as glucose, water, and small hydrophobic molecules like gases and hormones, as well as various leukocytes. Continuous capillaries not associated with the brain are rich in transport vesicles, contributing to either endocytosis or exocytosis. Those in the brain are part of the blood-brain barrier. Here, there are tight junctions and no intercellular clefts, plus a thick basement membrane and astrocyte extensions called end feet; these structures combine to prevent the movement of nearly all substances.
Figure 4. The three major types of capillaries: continuous, fenestrated, and sinusoid. A fenestrated capillary is one that has pores or fenestrations in addition to tight junctions in the endothelial lining. These make the capillary permeable to larger molecules. The number of fenestrations and their degree of permeability vary, however, according to their location. Fenestrated capillaries are common in the small intestine, which is the primary site of nutrient absorption, as well as in the kidneys, which filter the blood.
A: Stimulus is the signal that causes changes in the membrane potential of an excitable cell. If the st A: The human skin is formed of layers like- epidermis, dermis and hypodermis. The epidermis is the oute Q: nerve cells characterized by. A: A neuron, also known as a nerve cell, is an electrically excitable cell that communicates with other Q: List and describe seven important functions of bones. A: A bone is a hard tissue We know that is a part of the vertebrate skeleton.
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A: Hormones are chemical messengers or signaling molecules that are secreted by various glands to help A: Arteries and veins are the two primary types of blood vessels in the body.
Arteries are blood channe Q: What is the rotator cuff? Name the muscles forming rotator cuff. A: Introduction: The contractile tissue responsible for movement is muscle.
Muscles can be regarded as A: Labored breathing can be problematic and effect you to feel exhausted. Q: Answer the following questions about the position of each organ on the torso model. The stomach i A: Since you have posted a question with multiple sub-parts, we will solve first three sub-parts for yo Q: joint True O False The external carotid artery terminates behind the neck of the mandible by div A: The common Carotid artery is the largest vessel which provides blood to the head and neck.
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Q: During the first two years, when do reflexes begin being replaced by voluntary actions? A: Since you have posted multiple questions, we will solve the first question for you. If you want any Q: What are the five roles that proteins can play as part of the plasma membrane?
A: The plasma membrane is the physical and chemical barrier, responsible for separating the intracellul Q: The following structures are not the. Inguinal ligament A: The inguinal canal is fenced by superior and inferior walls and anterior, posterior. Q: Epithelial cells that reabsorb solutes are cuboidal, but epithelial cells involved in filtration are A: Epithelial cells are the cells that line your body's surfaces.
They live on your skin, blood vessels Q: Describe the neurotransmitters shown in Section
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