Although mom controls the oxygen source, the fetus has a couple of clever tricks to get the most oxygen possible! Rishi is a pediatric infectious disease physician and works at Khan Academy.

This lesson describes how the circulatory system works, including the heart, blood vessels and blood. Students learn about the chambers and valves of the heart, the difference between veins and arteries, and the different components of blood. This lesson also covers the technology engineers have developed to repair the heart if it is damaged. Students also understand how the circulatory system is affected during spaceflight (e.g., astronauts lose muscle in their heart during space travel).

Heterophils are the most abundant granulocyte in most avian species and occur alongside lymphocytes, monocytes, eosinophils and basophils in avian blood. These cells are also found in some reptile and mammalian species.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"Blood transfusions these days are generally very safe. But they can still cause serious harm with a condition called transfusion-related acute lung injury, or TRALI. TRALI is a leading cause of death related to the use of blood products. A new review in the journal Anesthesiology provides an overview of the condition and makes the case for why anesthesiologists should be on the front lines fighting it. Classically, TRALI is defined as a lung injury occurring within 6 hours of a blood transfusion. Onset can also be delayed 24 to 72 hours in critically-ill patients in the I-C-U or O-R. TRALI is not fully understood, but is frequently described as a 2-hit process. Baseline inflammation within the recipient establishes increased risk, in part due to neutrophils in the lungs..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

This text been designed for an undergraduate human anatomy and physiology course at a medium sized public university. This text has been modified from the original OpenStax text to encourage more active reading for an early undergraduate student taking the first semester of a year-long human anatomy and physiology course sequence. This text has been targeted to our student population, consisting primarily of first semester pre-nursing and kinesiology majors at a university with a high proportion of first generation and PELL-eligible students who benefit from lower barriers to entry into the field. Therefore, freely-available and differently presented text can be beneficial to this student population. This version was designed with the intention of distributing it section by section through a learning management system. If this mode of distribution is used, connection to an assessment tool could be utilized. Systems covered include skeletal, muscular, cardiovascular, respiratory, and nervous.

As this text reorganizes and modifies an OpenStax’s Anatomy and Physiology 2e (see related resources link below), chapter numbers and chapter section numbers from the original have been preserved in this document. Material supplemented from other sources is cited within the text.

Course connections: Undergraduate courses aimed towards freshmen or sophomore, including Anatomy and Physiology, Introduction to Anatomy and Physiology, Physiology, Introduction to Physiology, Human Biology or similar with a human focus.

Lysozyme is one of the major bactericidal agents in secretions and particularly helps to protect vulnerable sites such as the eyes and nasal passages. The lysoszyme exerts bactericidal effects by digesting bacterial cell walls. The complement system is a group of about 30 proteins within the body fluids of all vertebrates and some invertebrates. The main functions of complement are to promote phagocytosis or causes lysis of an invading organism.

IgA is present at low concentrations in plasma, and has minimal function inside the body. However, it is specially adapted for action at mucosal surfaces and as such, is present in high concentrations in mucosal secretions and in colostrum (and milk). In many species (dogs, cats and pigs), it is the major antibody in

IgD is present in ruminants, pigs, dogs and rodents but has not been identified in horses, cats, rabbits and chickens. It is mainly expressed on the surface of B-cells i.e. it is never secreted.

Unlike IgM, IgG and IgA, IgE does not function as a soluble antibody, with binding to Fc? receptors required before it can bind to the target antigen, and is found in low levels in blood plasma. Like IgA, it is produced by plasma cells and is mainly localised to mucosal surfaces.

IgG is the major antibody in blood plasma, and constitutes at least 80% of all antibodies in the body. It is the smallest immunoglobulin, so can readily leave the blood plasma and enter tissues. They can also cross the placenta, providing adaptive immunity to the foetus when the mother is under attack. IgG is also present in breast milk.

IgM is the primordial antibody and, although a monomer, is secreted as a pentamer (five monomers joined by disulphide bonds with two monomers joined by a J chain). This gives it ten identical antigen binding sites although IgM usually has relatively low affinity for its antigen. Its heavy chain is type mu (ľ).

Also called antibodies, Immunoglobulins (Ig) are the soluble form of B cell receptors (BCR) released by plasma cells after they have been activated. Immunoglobulins have to bind to a number of different antigens in a variety of environments and as such there are several different immunoglobulin classes. Each class has an optimum environment of action.

Both the innate and adaptive immune systems use receptors to recognise foreign organisms. The innate immune system uses pattern recognition receptors which acts as an early warning system. The adaptive immune response is highly specific for each organism, as B and T cells have specialist surface immunoglobulin receptors which detect specific antigens on foreign pathogens. The Innate immune system is the body's first barrier of defence to infection. It relies on an older, more generic, and faster acting set of tools than the adaptive system. While the adaptive system is essential for a specific response to infection, it is ultimately the innate system that conquers foreign attackers through means of phagocytosis.

The simplest way to avoid infection is to prevent microorganisms gaining access to the body. The skin has an external coating of dead cells (cuticle) that, when intact, is impermeable to most infectious agents as very few pathogens are capable of penetrating the thick stratified squamous epithelium of the skin (and lower urinary tract).

Pathogens can invade the body if a breach occurs in the barriers formed by the skin and mucus membranes, for example a wound, they must be detected and destroyed by cellular and humoral means. The cells involved in the cellular response to a wound are mast cells, macrophages, granulocytes, and monocytes.

The innate response to bacterial infection lies in its first-response role of detection of a foreign organism. By using the tools of Pattern-Recognition Receptors (PRRs), the innate response flags up problems while the adaptive response gets itself organized.

Because viruses invade host cells to take over a host's cellular machinery, the innate system has a more difficult time detecting viruses as foreign agents. However, there is a give-away element of the viral attack that the innate system can recognize: the double-stranded RNA (dsRNA) produced by a virus in its replication phase. Because mammalian cells only ever produce single-stranded RNA, the presence of dsRNA signals a foreign intruder. dsRNA can be detected by TLR-3R on the cell surface or intracellularly by the presence of dsRNA-dependent protein kinase.

Using ordinary household materials, student “biomedical engineering” teams design prototype models that demonstrate semipermeability under the hypothetical scenario that they are creating a teaching tool for medical students. Working within material constraints, each model consists of two layers of a medium separated by material acting as the membrane. The competing groups must each demonstrate how water (or another substance) passes through the first layer of the medium, through the membrane, and into the second layer of the medium. After a few test/evaluate/redesign cycles, teams present their best prototypes to the rest of the class. Then student teams collaborate as a class to create one optimal design that reflects what they learned from the group design successes and failures. A pre/post-quiz, worksheet and rubric are provided.