What is Blood: Definition and 334 Discussions

Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.In vertebrates, it is composed of blood cells suspended in blood plasma. Plasma, which constitutes 55% of blood fluid, is mostly water (92% by volume), and contains proteins, glucose, mineral ions, hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and blood cells themselves. Albumin is the main protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are mainly red blood cells (also called RBCs or erythrocytes), white blood cells (also called WBCs or leukocytes) and platelets (also called thrombocytes). The most abundant cells in vertebrate blood are red blood cells. These contain hemoglobin, an iron-containing protein, which facilitates oxygen transport by reversibly binding to this respiratory gas and greatly increasing its solubility in blood. In contrast, carbon dioxide is mostly transported extracellularly as bicarbonate ion transported in plasma.
Vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, instead of hemoglobin. Insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this "blood" does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their tracheal system to suffice for supplying oxygen.
Jawed vertebrates have an adaptive immune system, based largely on white blood cells. White blood cells help to resist infections and parasites. Platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system.
Blood is circulated around the body through blood vessels by the pumping action of the heart. In animals with lungs, arterial blood carries oxygen from inhaled air to the tissues of the body, and venous blood carries carbon dioxide, a waste product of metabolism produced by cells, from the tissues to the lungs to be exhaled.
Medical terms related to blood often begin with hemo- or hemato- (also spelled haemo- and haemato-) from the Greek word αἷμα (haima) for "blood". In terms of anatomy and histology, blood is considered a specialized form of connective tissue, given its origin in the bones and the presence of potential molecular fibers in the form of fibrinogen.

View More On Wikipedia.org
  1. Ahmedbadr132

    Do all bactriophages cross the blood brain barrier?

    Hi Bactriophages can cross the blood brain barrier but do all of them cross? They are very diverse.
  2. Valentina Chianese

    B Understanding the Rheopectic Properties of Blood: Fact or Fiction?

    Hello everyone, I need your help. A teacher once told me that blood is a non-Newtonian, rheopectic, pseudo plastic fluid. I get the non-Newtonian/pseudo plastic part, but I can't understand why blood is rheopectic...is it or not? Thanks
  3. red65

    Medical Exploring Blood Pressure: Measuring Hydrostatic Pressure?

    Hello everyone, concerning blood pressure , we know that the pressure exerted by moving fluid has two components: a dynamic, flowing component that represents the kinetic energy of the system, and a lateral component that represents the hydrostatic pressure (potential energy) exerted on the...
  4. samy4408

    Medical The impact of the sympathetic nervous system on blood vessels

    Hello, I have some trouble understanding the role of the sympathetic nervous system in vasoconstriction and vasodilatation of blood vessels, I searched and found contradicting resources, does anyone have the right answer?
  5. Superlieutenant1

    Physics of Blood Pressure and Blood Energy

    Hello I am a physiology student who is curious about the physics underyling blood flow and pressure. I have taken physics classes however at the elementary level the focus is on ideal fluids in systems with no friction. I would appreciate any answers or if you could point me in the right...
  6. T

    Long COVID - Blood Markers linked to Mental Problems

    Viral particles linger in brain cells. The analysis detected much higher average levels of two SARS-CoV-2 viral proteins they measured—the nucleocapsid protein and the spike protein—in blood plasma samples collected between six and 12 weeks after diagnosis from patients infected with COVID who...
  7. J

    EMF generated in a blood cell by an oscillating magnetic field

    At first I tried plugging everything in with 60Hz in the numerator but that did not work. I was told to think about sinusoidal waves and derivates but I'm not sure how that works. Any ideas? Thanks a lot
  8. jaumzaum

    Understanding Increase in Peripheral Resistance & Blood Pressure

    Hello guys, can anyone help me to understand why an increase in peripheral resistance causes an increase in the blood pressure? If we assume the equation Delta P = R times Q If we assume Q is constant, the greater the resistance the greater the the decrease in pressure, so the pressure should...
  9. A

    Spike protein level in blood, vaccinated vs. infected study

    So I'll try to be brief. There is a recent study that is titled "Immune imprinting, breadth of variant recognition, and germinal center response in human SARS-CoV-2 infection and vaccination" https://www.sciencedirect.com/science/article/pii/S0092867422000769 Among other stuff it has measured...
  10. NTL2009

    Please help explain this Blood Pressure Monitor 'calibration' system

    I've wanted to check the accuracy of my Blood Pressure Monitor (BPM) (an automated Omron unit), and finally found this old (2016) thread on another site (linked below). Prior to this, I only found the less helpful 'compare the reading to your Doctor's office' (BP varies with every reading, not...
  11. berkeman

    How are blood glucose monitoring modules installed in arms?

    My wife asked me a good question, and even with moderate Google searching I couldn't answer her question about how the patches are installed in arms. How do these BGL monitoring patches work? Thanks...
  12. Lakkana

    Can isopropyl alcohol Blood clots soluble ?

    I have old cuts I put rubbing isopropyl alcohol on it, it cleaned slowly and vanish the blood clots, I would likes to know can isopropyl alcohol Blood clots soluble?
  13. Q

    MHB Probability of O & AB Blood Types

    The blood groups of 200 people are distributed as follows: 40 have type A blood, 75 have type B blood, 60 have type O blood, and 25 have type AB blood. If a person from any of the group is selected at random, what is the probability that this person has an O blood type? How about the AB blood...
  14. yourheartandsoul

    Finding blood pressure from density and height difference

    I did (1300)(9.81)(0.67) and got 8544.51 N/m^2 but unsure if that was the correct route to take. Please confirm or deny if I was approaching it in the correct way!
  15. nomadreid

    Does OK hemoglobin make a low level of iron in blood OK?

    Suppose a blood test shows a value of 41 milligrams per deciliter, with a healthy range between 65-175, yet the hemoglobin levels in the same blood test are perfectly normal, as well as are other indicators in the blood test. A doctor explained that one would not need to be worried about the...
  16. K

    Puncturing blood vessels - elasticity?

    Hi all! :) I'm a physician who regularly punctures blood vessels with needles. This is successful when the needle punctures the superficial surface to enter the lumen, but does not puncture the deep surface. If this happens, nearby structures (lung, nerves, heart) are damaged. Increasing force...
  17. T

    Blood Urea Nitrogen (BUN): Why Increases with Age & How to Decrease It?

    Why do blood urea nitrogen (BUN) increases with age ? Can it be decreased?
  18. D

    How long does it take to pass out from blood loss and bleed out?

    Hi everyone I'm writing a story in which someone passes out from blood loss before they are found and saved. How long might a rescuer have before the victim dies? I'm guessing there might be a lot of variables here, but I'm just looking for the longest possible realistic delay. Also, if...
  19. Ygggdrasil

    Medical Progress for Gene Therapy and CRISPR against Blood Diseases

    The New England Journal of Medicine published two papers showing data for successful treatment of a handful of patients with sickle cell disease or β- thalassemia using gene therapy techniques. Both teams used the strategy of inhibiting the BCL11a transcription factor in blood cells, which...
  20. aryan15

    Physics Pressure Problem (Systolic blood pressure of a giraffe)

    Absolutely no idea how to go about this question. An answer with an explanation would be highly appreciated. Thanks!
  21. mktsgm

    Medical How is blood volume calculated and measured in the human body?

    We know that we humans have roughly 5 liters of blood circulating in our body. The volume also may be varying. We also know that its volume is tightly regulated and multiple organs are involved in it. My question is, how we calculated that we have 5 liters of blood? Is it an approximation or...
  22. mktsgm

    Medical How are normal values of blood pressure and glucose determined?

    Blood glucose is measured and compared against a set of standard/normal values (like, fasting 100 mg/dL etc) to determine if a person has hyperglycemia or not. Similarly Blood pressure readings (systolic & diastolic) are also compared against another set of standard/normal values like 120/80...
  23. T

    New Blood Test for Alzheimer Disease

    The Journal of the American Medical Association (JAMA) today (7/28/2020) published an article on using presence of phospho-tau217 (p-tau217) in blood plasma to detect Alzheimers Disease. Over 80% specificity, and early results look like it could be predictive up to 20 years...
  24. Wrichik Basu

    Medical Do statins permanently reduce LDL levels in blood?

    Statins are often prescribed by doctors to people who have a high level of LDL in their blood. I have also read that statins help in boosting HDL to some extent, but that is not of interest in this thread. Consider the case where a person has been prescribed statin by a doctor. After two...
  25. hagopbul

    Medical Question about a biosensor for decting coronavirus in saliva or in blood

    hello all : there was this technology that i read about maybe a year ago, could it help in better technology fast and reliable method to detect corona virus in saliva or in blood ? http://web.mit.edu/degenlab/index.html http://web.mit.edu/degenlab/degenlab_techniques.html...
  26. S

    Mercury vapor from blood pressure devices

    I came across some articles about the health hazard from broken mercury-based sphygmomanometers. This led me to think about vapor leakage from good devices during normal operation. The top of the glass tube is at ambient atmospheric pressure. There is supposed to be a membrane at the top that...
  27. B

    Can a humanoid alien race have combustible blood?

    Was wondering this for a scifi alien race I have in mind, is it chemically possible to have a race with combustible blood.? The answer: Yes, but I wonder how close the blood will be to our own? Since oxygen carrying blood like ours is preferred since it can deliver more energy for the work the...
  28. E

    Japanese scientists create artificial blood

    Scientists in Japan create an artificial blood that could potentially be given to all blood types. https://www.iflscience.com/health-and-medicine/japanese-scientists-create-artificial-blood-that-could-potentially-be-given-to-all-blood-types/
  29. Asuratyr

    I Can red blood cells be considered colloids? (soft matter physics)

    Hi, I was studying soft matter physics when a question arose between a friend and me. Namely if red blood cells can be considered to be a colloid. Colloids as it was presented to us had 3 criteria: high diffusion so the particles wouldn't form a sediment, a small reynolds number and a surface...
  30. Skyland

    Writing: Input Wanted Blood Moon (Concept): Discovering Ferron & Terrelectra

    This is the official thread for my scifi project Blood Moon (running name, likely to change) **Since my earlier thread got moved here, I might as use this new thread as a starting point for the whole project, and limit usage of the other threads for more specific inquiries about certain...
  31. C

    Is the blood supply distinctive or collateral per organ?

    Hello! Is the blood supply to an organ done exclusively by one (or more) distinct arteries or there is extensive collateral supply from different arteries? For example, is lungs' circulation only from bronchial and pulmonary arteries/veins or there is collateral blood circulation as well from...
  32. jaumzaum

    Why A, B or O can donate blood to AB?

    AB people don't have agglutinins anti A or anti B so it might seem they can receive any type of blood. But if the donator is A for example, it's own blood will have agglutinins anti B that will agglutinate the AB blood. So why can AB people receive blood from non AB people?
  33. F

    Blood flow velocity via Doppler effect

    Homework Statement A Doppler flow meter is used to measure the speed of red blood cells. The frequency of the apparatus is f = 12 MHz. The sensor in the apparatus measure 1.8 kHz beats between the emitted frequency and the frequency of the ultrasound reflected back by the blood cells. The speed...
  34. C

    Are there organelle parts circulating blood?

    Hello, Once reading about renal function I think, I read that there are actually parts from organelles circulating in blood that have a specific name. They also function as messengers. But I cannot find anything about it now, any idea?
  35. S

    Solving the Speed of Blood Flow in a Magnetic Field

    1. The question... "Blood is a conducting fluid. When flowing through an artery of diameter 10mm which is subject to a constant magnetic field of strength 60mT, an e.m.f. of 0.3mV appears across the width of the artery. Calculate the speed of the blood" 3. The solution... The solution given...
  36. axer

    Pressure of blood in an artery

    Homework Statement The average pressure of the blood in a person’s arteries is 100 mmHg. What is the average pressure in an artery in the head of standing person 40 cm above the heart? (blood density= 1.05x103 kg/m3,Mercury density = 13.6x103 kg/m3 and g=10 m/s2) Homework EquationsThe...
  37. R

    How Far Can a Shark Smell Blood in the Ocean?

    I have read that a shark has great sensitivity to smelling blood from a large distance. In an open, calm sea, just how fast can blood molecules diffuse through sea water for a shark to detect??
  38. P

    Do you think my dog has wolf blood in her (DNA testing)

    My supposed malamute/golden eyes (75-25%) Wolf eyes... My dog again.. She exhibits several signs of characteristic wolf behavior including hypersensitivity to stimulus, is extremely skittish etc Would you bet she has 5-10% actual wolf blood in her when the results are in?
  39. José Ricardo

    Medical Red blood cells can turn into a sperm or an egg?

    With the advances of science, will it be possible to turn red cells into sperm or turn them into eggs to help a man who has lost both testicles or a woman who has lost her ovaries?
  40. berkeman

    Breath Control and Blood Pressure

    When I free dive (skin dive without a scuba air tank), I've noticed that by the time I get out of the water after about an hour (abalone diving or just recreational free diving), I feel like Jello and my blood pressure (BP) feels very low. I feel extremely relaxed and warm and happy. And after...
  41. Asmaa Mohammad

    Characteristics of different types of hypoxia

    Hello, My book illustrates characteristics of different types of hypoxia in this table Arrows directed upwards indicate an increase and vice versa. I know what each type of hypoxia is, but I find a difficulty understand the change in venous PO2, O2 content and saturation of hemoglobin in...
  42. BillTre

    Blood Donor in Australia Affected Millions

    Here is a CNN article about James Harrison, a guy in Australia, who started donating blood when he was 14 (after he had an operation and required blod transfusions). He has aged out of being acceptable for donating blood at 81. He is considered the GOAT (Greatest Of All Time) Australian blood...
  43. berkeman

    Quieter Korotkoff sounds when taking blood thinners?

    I have a patient that I have known for a long time, and her Korotkoff sounds have always been pretty typical in volume when I've taken her blood pressure. But after a recent medical incident, her doctor has put her on a long-term blood thinner medication. I was taking her BP a couple of days...
  44. mktsgm

    Medical Blood antigens -- pregnant mothers' blood types and infants' blood types

    I have a small question regarding pregnant mother's blood types and infant's blood types. We all know the if an Rh-ve mother carries an Rh+ve child, there is a possibility that their blood may mix during the delivery. This may induce some (Rh D) antibodies in maternal blood. In case the same...
  45. Psinter

    Why doesn't blood dry inside our bodies?

    Legit question. When we get a cut or scrap, blood comes out. In a few moments the blood dries and forms what looks like a layer of dried blood that gets a darker color. If that happens, why doesn't blood dry inside our bodies?
  46. BillTre

    Immune Cells Involved with High Blood Pressure

    High blood pressure can affect health in many ways. No one treatment can control it in all cases. Treating immune cells may help control it. Science mag news article here.
  47. lekh2003

    Super Blue Blood Moon: Did Anyone See It?

    I just wanted to see anybody's opinion on the super blue blood moon yesterday night (at least for me). I couldn't catch a glimpse of it in Sydney since it had been very hot for a few days and clouds had taken over the sky. I could however see an unusually bright red tint in one area of the...
  48. BillTre

    Is Home Testing for Cancers with a Blood Assay a Good Idea?

    Science magazine news reports on a blood assay for a number of cancers, done all at once. It detected between 33% and 98% of cases with <1% false positives. it uses a combination of detecting DNA and proteins.
  49. H

    Laminar and turbulent flow on dripping blood

    Can laminar and turbulent flow be used to explain dripping blood? Be it blood dripping from a weapon/ impacting on an uneven surface?
  50. jaechung

    Why Do Blood Pressure Levels Vary Throughout the Cardiovascular System?

    Hi, I am studying about blood pressure. And I have some questions. The blood pressure in the left ventricle is about 105mmHg, and that in the right atrium is about 0 to 2 mmHg, Why do pressures decrease through our vasculature? And what kind of pressures are the pressures in the blood? Is it...