Human Physiology: An Integrated Approach 5th Ed. - Ch. 3

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Biological Sciences

Chapter 3 Notes Biological compartments = varied o Some come are completely enclosed structured Ex. cells o Some dont even have visible walls Development of life: o Simple cell w/ only ICF and membrane intracellular compartments developed w/ their own membranes single-celled organisms cooperated and specialized their functions thus giving rise to multicellular organisms as multicellular organisms became more complex and larger, many separate functional compartments formed Pros and cons to compartmentation: o Pros: Biochemical processes that would conflict w/ e/o are separated from e/o Contents in one compartment can differ from contents in another compartment, even for adjacent compartments o Cons: Barriers make it hard for needed materials of one compartment to move to that compartment Functional Compartments of the Body Human body has 3 major body cavities: 1. Cranial cavity (skull) [cranium, skull) Contains the brain, our PRIMARY control center 2. Thoracic cavity (thorax) Bounded by the spine and ribs on top and sides, w/ the muscular diaphragm forming the floor Surrounds the heart and the lungs Heart is enclosed in a membranous pericardial sac [peri-, around + cardium, heart]; both lungs are enclosed in separate pleural sacs 3. Abdominopelvic cavity Abdomen and pelvis form one continuous cavity The peritoneum, a tissue lining, lines the abdomen and surrounds the organs within it (stomach, intestines, liver, pancreas, gallbladder, and spleen) The kidneys lie OUTSIDE the abdominal cavity, b/w the peritoneum and the muscles and bones of the back, just above the waist level The pelvis contains reproductive organs, the urinary bladder, and the end portion of the large intestine o these cavities are separated by bones and tissues, and theyre lined w/ tissue membranes --------------------------------------------------------------------------------------------- the lumens of some organs are outside the body the heart, lungs, blood vessels, and intestines are all HOLLOW organs, thus creating another set of compartments within the body o lumen: the interior of any HOLLOW organ [lumin, window] a lumen may be completely or partially filled w/ air or fluid ex. blood vessels are filled w/ blood, a fluid for some organs, the lumen is pretty much an extension of the external environment ex. the digestive tracts not really inside our body; its lumen is part of the bodys external environment to understand this, just think of a hole through a bead; the hole passes through the bead, but isnt actually inside the bead ------------------------------------------------------------------------------------------------- Functionally, the body has three fluid compartments Most cells ARE NOT in direct contact w/ the outside world o Theyre, instead, surrounded by ECF We can think of the body as being composed of 2 units: the cells that compose the body, and the fluid that surrounds them o Using this concept of the body, we can divide the body into TWO compartments: The intracellular fluid (ICF) in the cells The extracellular fluid (ECF) outside the cells ECF can be further divided into compartments: o plasma: fluid portion of the blood lies within the circulatory sys o interstitial fluid [inter-, b/w + stare, to stand]: lies b/w the circulatory sys and the cells These two compartments are separated by the barrier of the cell membrane note that even though weve considered cells to be of a single fluid compartment, they are highly variable in size, shape, and composition Biological Membranes membrane [membrana, a skin] has two meanings in biology: a. (before invention of microscopes) a tissue that lines a cavity or separates 2 compartments i. ex. mucous membrane, peritoneal membrane, pleural membrane ii. VISIBLE, thin, translucent layers of cells b. (after invention of microscopes) once scientists recognized a barrier b/w the intracellular fluid and external environment of cells, they had concluded that the outer surface of cells (cell membrane) was a thin layer of lipids that separated the internal aqueous fluids from the external environment thus, membrane can refer to EITHER a tissue OR to a phospholipid-protein boundary layer (NOTE THAT THEY DO NOT HAVE THE SAME STRUCTURES) ------------------------------------------------------------------------------------ The cell membrane separates the cell from its environment Gen functions of the cell membrane include: o Physical isolation: cell membrane = physical barrier which separates the ICF from the ECF o Regulation of exchange w/ the environment: the cell membrane controls the entry of ions and nutrients into the cell, the elimination of cellular wastes, and the release of products from the cell o Communication b/w the cell and its environment: proteins IN the cell membrane let the cell recognize and respond to molecules or to changes in the external environment; thus, any change in the cell membrane may affect the cells functionality o Structural support: proteins in the cell membrane hold the cytoskeleton (the cells internal structural material) in place to maintain cell shape Membrane proteins also create specialized junctions b/w adjacent cells or b/w cells and the extracellular matrix (extra, outside) which is extracellular material thats synthesized and secreted by the cells (secretion = when a cell releases a substance into the extracellular space) Cell-cell and cell-matrix junctions stabilize the structure of tissues ------------------------------------------------------------------------ Membranes are mostly lipid and protein A cellular membranes properties varies throughout the body, and mostly depends on the molecular arrangement of the proteins and lipids in the various membranes o The ratio of protein to lipid varies widely, depending on where the membranes cell is found in the body (See pg. 57 Table 3-1)
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