Health Facts

  The fluid mosaic model describes the plasma membrane structure as a mosaic of phospholipids, cholesterol, proteins,  Note: The main fabric of the membrane is composed of amphiphilic or dual-loving, phospholipid molecules. Integral proteins, the second major component of plasma membranes, are integrated completely into the membrane structure with their hydrophobic membrane-spanning regions interacting with the hydrophobic region of the phospholipid bilayer. Carbohydrates, the third major component of plasma membranes, are always found on the exterior surface of cells where they are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids).   Terminologies  Hydrophobic : Lacking an affinity for water; unable to absorb, or be wetted by water, "water-fearing." Hydrophilic : Having an affinity for water; able to absorb, or be wetted by water, "water-loving." Amphiphilic : Having one surface consisting of hydrophilic amino acids and the opposit...

  Structure of Plasma Membranes The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is a biological membrane that separates the interior of a cell from its outside environment. The primary function of the plasma membrane is to protect the cell from its surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells. Plasma membranes must be very flexible in order to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries. The plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix and other cells to help group cells together to form tissues. The membrane also maintains the cell potential. In short, if the cell is represented by a castle, the plasma membrane is the w...

  Cells as the Basic Unit of Life A cell is the smallest unit of a living thing and is the basic building block of all organisms. Key Points : A living thing can be composed of either one cell or many cells. There are two broad categories of cells: prokaryotic and eukaryotic cells. Cells can be highly specialized with specific functions and characteristics.   Terminologies   prokaryotic Small cells in the domains Bacteria and Archaea that do not contain a membrane-bound nucleus or other membrane-bound organelles. eukaryotic Having complex cells in which the genetic material is contained within membrane-bound nuclei. Cell The basic unit of a living organism, consisting of a quantity of protoplasm surrounded by a cell membrane, which is able to synthesize proteins and replicate itself. Close your eyes and picture a brick wall. What is the basic building block of that wall? A single brick, of course. Like a brick wall, your body is composed of basic building blocks, and the ...

  Body Cavities Vertebrates have fluid-filled spaces called body cavities that contain the organs.  NB: i. The dorsal cavity contains the primary organs of the nervous system, including the brain and spinal cord. ii. The diaphragm is a sheet of muscle that separates the thoracic cavity from the abdominal cavity. iii. Special membrane tissues surround the body cavities, such as the meninges of the dorsal cavity and the mesothelium of the ventral cavity. iv.  The mesothelium consists of the pleura of the lungs, the pericardium of the heart, and the peritoneum of the abdominopelvic cavity. Terminologies  1. Thoracic Cavity :The ventral body chamber that contains the pericardial cavity (the heart) and the pleural cavity (the lungs). 2. Dorsal cavity : The cavity in the back of the body that contains the cranial and vertebral cavities, which house the brain and spinal cord respectively. 3. Abdominoplevic cavity : The ventral body chamber that contains the abdominal cavity...

 Navigating Anatomy with Language Directional terms provide precise descriptions of a structure's location. They allow a description of anatomical position by comparing location relative to other structures or within the rest of the body. Standard anatomical terms for direction include: 1. Superior and inferior (cranial and caudal) are used when referring to parts of the body which are toward an end of the body. Superior structures are toward the head (cranial) while inferior (caudal) structures are toward the feet. Examples include the superior and inferior vena cava, which carry deoxygenated blood away from the head (superior) and from the lower body (inferior) to the heart. 2. Anterior and posterior are sometimes used in place of superior and inferior, respectively. These words are used more often for animal anatomy and rarely and only with very specific meaning in human anatomy. Anterior refers to the side of the structure facing up in the standard anatomical position while pos...

                  Anatomical Position When an organism is in its standard anatomical position, positional descriptive terms are used to indicate regions and features. Key Points In standard anatomical position, the limbs are placed similarly to the supine position imposed on cadavers during autopsy. The anatomical position of the skull is the Frankfurt plane. In this position, the lower margins of the orbitals (eye sockets), the lower margin of the orbits, and the upper margins of the ear canals (poria) lie in the same horizontal plane. Because animals can change orientation with respect to their environments and appendages can change position with respect to the body, positional descriptive terms refer to the organism only in its standard anatomical position to prevent confusion. Key Terms Appendage : A limb of the body. Anatomical position : The standard position in which the body is standing with feet together, arms to the side, and head, ...

  If positive and negative feedback loops are affected or altered, homeostatic imbalance and resultant complications can occur. What Is Disease? Disease is any failure of normal physiological function that leads to negative symptoms. While disease is often a result of infection or injury, most diseases involve the disruption of normal homeostasis. Anything that prevents positive or negative feedback from working correctly could lead to disease if the mechanisms of disruption become strong enough. Aging is a general example of disease as a result of homeostatic imbalance. As an organism ages, weakening of feedback loops gradually results in an unstable internal environment. This lack of homeostasis increases the risk for illness and is responsible for the physical changes associated with aging. Heart failure is the result of negative feedback mechanisms that become overwhelmed, allowing destructive positive feedback mechanisms to compensate for the failed feedback mechanisms. This l...

 Concept of Homeostasis Homeostasis regulates an organism's internal environment and maintains a stable, constant condition of properties like temperature and pH. Homeostasis can be influenced by either internal or external conditions and is maintained by many different mechanisms. All homeostatic control mechanisms have at least three interdependent components for the variable being regulated:  1. A sensor or receptor detects changes in the internal or external environment. An example is peripheral chemoreceptors, which detect changes in blood pH. 2. The integrating center or control center receives information from the sensors and initiates the response to maintain homeostasis. The most important example is the hypothalamus, a region of the brain that controls everything from body temperature to heart rate, blood pressure, satiety (fullness), and circadian rhythms (sleep and wake cycles). 3. An effector is any organ or tissue that receives information from the integrating ce...

 Human physiology is the study of the mechanical, physical, and biochemical processes that support the body's function. The study of physiology occurs at many levels, including organisms, organ systems, organs, cells, and biomolecules. Physiology investigates the processes and mechanisms that allow a living thing to survive, grow, and develop. Homeostasis is the maintenance of the overall stability of physiological processes of the body. It is monitored by the brain and nervous system and regulated by the physiology and activity of individual organs. While anatomy deals with the structure of the parts of an organism, physiology studies the way that the parts function together. Terminologies  physiology : A branch of biology that deals with the functions and activities of living matter and the physical and chemical processes and mechanisms involved. Living Systems : Open, self-organizing living things that interact with their environments. These systems are maintained by flows ...

 Human anatomy is the study of the structure of the human body. Gross anatomy is subdivided into surface anatomy (the external body), regional anatomy (specific regions of the body), and systemic anatomy (specific organ systems). Microscopic anatomy is subdivided into cytology (the study of cells) and histology (the study of tissues). Anatomy is closely related to physiology (study of function), biochemistry (chemical processes of living things), comparative anatomy (similarities and differences between species), and embryology (development of embryos). Knowledge of anatomy is needed to understand human biology and medicine. Key Terms surface Anatomy The study of anatomical landmarks that can be identified by observing the surface of the body. Sometimes called superficial anatomy. anatomy The study of the body structure of animals. dissection The process of disassembling an organism to determine its internal structure and understand the functions and relationships of its components...