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By the end of this section, you will be able to:
  • Describe the anatomy of erythrocytes
  • Discuss the various steps in the lifecycle of an erythrocyte
  • Explain the composition and function of hemoglobin

The erythrocyte    , commonly known as a red blood cell (or RBC), is by far the most common formed element: A single drop of blood contains millions of erythrocytes and just thousands of leukocytes. Specifically, males have about 5.4 million erythrocytes per microliter ( µ L) of blood, and females have approximately 4.8 million per µ L. In fact, erythrocytes are estimated to make up about 25 percent of the total cells in the body. As you can imagine, they are quite small cells, with a mean diameter of only about 7–8 micrometers ( µ m) ( [link] ). The primary functions of erythrocytes are to pick up inhaled oxygen from the lungs and transport it to the body’s tissues, and to pick up some (about 24 percent) carbon dioxide waste at the tissues and transport it to the lungs for exhalation. Erythrocytes remain within the vascular network. Although leukocytes typically leave the blood vessels to perform their defensive functions, movement of erythrocytes from the blood vessels is abnormal.

Summary of formed elements in blood

This table shows the different types of cells present in blood, the number of cells, their appearance, and a summary of their function.

Shape and structure of erythrocytes

As an erythrocyte matures in the red bone marrow, it extrudes its nucleus and most of its other organelles. During the first day or two that it is in the circulation, an immature erythrocyte, known as a reticulocyte    , will still typically contain remnants of organelles. Reticulocytes should comprise approximately 1–2 percent of the erythrocyte count and provide a rough estimate of the rate of RBC production, with abnormally low or high rates indicating deviations in the production of these cells. These remnants, primarily of networks (reticulum) of ribosomes, are quickly shed, however, and mature, circulating erythrocytes have few internal cellular structural components. Lacking mitochondria, for example, they rely on anaerobic respiration. This means that they do not utilize any of the oxygen they are transporting, so they can deliver it all to the tissues. They also lack endoplasmic reticula and do not synthesize proteins. Erythrocytes do, however, contain some structural proteins that help the blood cells maintain their unique structure and enable them to change their shape to squeeze through capillaries. This includes the protein spectrin, a cytoskeletal protein element.

Erythrocytes are biconcave disks; that is, they are plump at their periphery and very thin in the center ( [link] ). Since they lack most organelles, there is more interior space for the presence of the hemoglobin molecules that, as you will see shortly, transport gases. The biconcave shape also provides a greater surface area across which gas exchange can occur, relative to its volume; a sphere of a similar diameter would have a lower surface area-to-volume ratio. In the capillaries, the oxygen carried by the erythrocytes can diffuse into the plasma and then through the capillary walls to reach the cells, whereas some of the carbon dioxide produced by the cells as a waste product diffuses into the capillaries to be picked up by the erythrocytes. Capillary beds are extremely narrow, slowing the passage of the erythrocytes and providing an extended opportunity for gas exchange to occur. However, the space within capillaries can be so minute that, despite their own small size, erythrocytes may have to fold in on themselves if they are to make their way through. Fortunately, their structural proteins like spectrin are flexible, allowing them to bend over themselves to a surprising degree, then spring back again when they enter a wider vessel. In wider vessels, erythrocytes may stack up much like a roll of coins, forming a rouleaux, from the French word for “roll.”

Questions & Answers

type 2 is controled by diet
Chloe Reply
Diet and life style
Diet how? maybe eating food containing less sugar?
what is hypotension
regina Reply
hypotension is when the blood pressure is less than 60/50
hypo means low so it implies low blood pressure
what is mild DKA
mild diabetic ketoacidosis is when there is high level of sugar in the blood and the ketone bodies build up in the body ,is a type 1 which can lead to type 2
what is the normal range for blood pressure?
120 over 80
low blood pressure; opposite of high blood pressure which is hypertension
what if your a type 2 diabetic and you have no way to get meds due to no insurance what is some good over the counter medications to take?
type 2 diabets is controlled by diet not meds.type 1 is contolled by insulin.
type 1 diabets cant be controlled type 2 can be controlled.type 1 is worse than type 2 diabets.
type 2 is purely a lifestyle disease, eat healthy, fresh, natural unprocessed real foods.
sometime , we already eat diabetic diet than the results of blood sugar level not turn good , what is the reason ?
What is a "diabetic diet" though? Be specific. Juvenile diabetes and/or Type 1 diabetes is something that one can be born with, this needs medical diagnosis and intervention.
what i mean by diabetic diet is we take fiber-rich food like vegetables,nut and also fish.
ok, no cause a doctor told me I needed metformin and my suger won't go under 300
what is the difference between plasma and serum
Gloria Reply
Plasma contains fibrinogen while serum doesn't
plasma ----- fibrinogen = serum
In what time stomach empty it's content in to doudemun? what is chyme?
Sneha Reply
write the chemical and mechanical digestion which occurs in stomach?
Does absorption take place in stomach? what are absorption in the stomach by which cell?
Chemical digestion---Mixtures of the food with the gastric acid Mechanical digestion--- churning of the food in the stomach making it become more involved into chyme
absorption takes place in the small intestine because of the presence of the villi
name the muscles supplied redina nerve
Appu Reply
mechanism of hormone releasing by gland
said Reply
why is muscle tissue not considered to be a type of connective tissue?
Ezel Reply
A Skeletal muscles consist of numerous muscles cells called Muscle Fibers . Three layers of connective tissues surrounded these fibers to make the muscles tissues
that's wny connective tissues is not considered as muscles fibers
there are 4 types of tissues : epithelial, connective tissue, nervous tissue and muscle tissue, each one has its own properties. The main function of connective tissue is nutrition, it supplies nutrientes to epithelial tissues that are responsible for protection.
Muscle tissue has properties that allow movement, the function here is movement and not nutrition like connective tissue.
In what time stomach empty it's content in to doudemun?
write the chemical and mechanical digestion which occurs in stomach?
Does absorption take place in stomach? what are absorption in the stomach by which cell?
Does absorption take place in stomach? what are the absorption in the stomach by which cell?
mechanism of hormone controlling releasing by gland
please can someone explain renin angiotensin aldosteron system for me
name the joint present between epichysif and diachysif
what is arteries
oxygenated blood carrying vessels
I think oxygenated blood carrying pulmonary vein
ya this stetment is right 4 pulmonary vein carrying the oxygenated blood
What is the relation between cold and clammy skin and disorders that cause poor perfusion?
Tyrone Reply
name the instruments used to measure the gas volume and flow in pulmonary function test
Preethi Reply
In a spirometry test, While you are sitting, you breath into a mouthpiece that is connected to an instrument called a spirometer . The spirometer records the amount and the rate of air that you breath in and out over a period of time. When standing, Some numbers might be slightly different.
tq soo much
u most wlcm
what is signal transduction?
Signal Transduction (Also know as cell signaling) is the transmission of molecular signal from a cell exterior to its interior.Signals receive by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell - surface receptors.
i know now didn't know
that's great respond
what is histological anatomy?
Thelma Reply
what is histological anatomy?
the study of form of structure seen under the microscope
is the branch of biology which studies the microscopic anatomy of biological tissues.
it's the study of the microscopic anatomy of cells and tissues in the plants and it's carried out by examining a thin slice of tissues under a microscope light / or an electronic microscope
is the study of anatomy in a microscopic level
thank you
what are the significance differrences can be donated between the female and male skeleton..
What is Ions and Ionic bonds
Ravi Reply
2 less stable atoms
Ionic bonding is the complete transfer of valence electron(s) between atoms. It is a type of chemical bond that generates two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively
what is osmosis
Brown Reply
it's out Body Fluid.
high pressure to low pressure flow
Osmosis is the movement of solvent from a region of lower solute concentration to a region of higher solute concentration through a semi- permeable membrane.
how many types of tissue
4, that is muscle tissue, connective, nerve and epithelial tissue
We have four types of tissue these are ,epithelial tissue,nerve tissue,muscle tissue and connective tissue
function of labia minora
why is a graph of plasma [glucose] superimposed
Sefai Reply

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