Biology 2 Flashcards
Bone structure
The outer covering of bones is a tough sheath called the periosteum. The periosteum contains blood vessels and bundles of collagenous fibers. Muscle ligaments and tendons may attach to the periosteum or directly to the compact bone.
Compact bone contains Haversian canals that run along the length of the bone. The Haversian canals contain blood and lymph vessels, nerves, and connective tissue. Around the Haversian canals, there are concentric layers of bony matrix called lamellae. An osteon consists of a Haversian canal plus the surrounding lamellae.
Spaces in the bony matrix called lacunae house osteocytes, or bone cells. The lacunae are linked to the Haversian canals via canaliculi.
Bone marrow is found in the central cavities of long bones. Red marrow contains stem cells, which form blood and immune cells. Yellow marrow is used to store fat.
Three types of joints
Immovable joints connect bones that don’ t move, for example, the bones of the skull.
Partly movable joints allow limited flexibility and usually have cartilage between the bones. An example is the joint between two vertebrae of the spinal column.
Synovial joints allow a wide range of movement and are lubricated by synovial fluid.
Muscles and skeletal system
Since muscle can only contract, and extension takes place only passively, muscles are found in antagonistic pairs. When one muscle in the pair contracts, the other relaxes
bone marrow
produces immune cells such as lymphocytes, monocytes, leukocytes, B cells and T cells
thymosin
thymus secretes thymosin, a hormone that stimulates pre-T cells to mature.
spleen
a storage area for blood, and also filters blood and lymph.
Interferons
released in response to viral infection. Interferons stimulate the production of proteins that interfere with viral replication
histamine
Injured cells release histamine, which causes blood vessels to dilate, resulting in increased blood flow to the site of damage. The inflammatory response is often accompanied by fever, which serves to retard bacterial growth, since many bacteria can only replicate within a specific temperature range.
B cell response
involves the production of antibodies, is sometimes called the humoral response, since the antibodies circulate through the fluids or “humors” of the body
T cell response
sometimes called the cellular response, since it involves the direct action of T cells
Three important types of T cells
- Cytotoxic T cells kill cells that are infected by a pathogen that the T cell recognizes.
- Helper T cells coordinate the immune response of other cells against specific antigens through the secretion of signaling molecules called lymphokines (for example, interleukins).
- Suppressor T cells regulate other T cells and B cells to decrease their activity
Antigens
substances that the immune system recognizes as foreign and mounts a response against.
antibodies
(immunoglobulins)
- proteins that recognize and bind to antigens
- Antibodies can attract other cells to phagocytize antigens, or cause the antigens to agglutinate (clump together), forming large, insoluble complexes that are removed by phagocytic cells.
Two main types of MHC are involved in the T cell response:
For an antigen to stimulate a T cell receptor, it must be presented to the cell as part of a complex of proteins called the MHC (Major Histocompatibility Complex) that is found in the plasma membrane of cells.
- MHC class I proteins are present on the surface of all cells.
- MHC class II proteins are only present on immune cells, including macrophages, B cells and T cells.
interleukins
- secreted when Helper T cells recognize the MHC-antigen complex on the surface of the macrophage
- Interleukins activate cytotoxic T cells to kill infected cells, and stimulate B cells to secrete antibodies
Plasma cells
specialized B cells that produce and secrete antibodies
(antibody protein factories)
Antibody Structure
