L5 Connective Tissue Cells And Immune Cells Flashcards
What is CT
connective tissue forms a continuum with epithelial tissue, muscle and nervous tissue as well as other components of CT to maintain a functionally integrated body
What is the origin of CT
From mesoderm in the middle germ layer of the embryonic tissue that contains mesenchymal stem cells (multi potent cells)
What are components of CT
Composed of cells and extra cellular matrix consisting of ground substance and fibers
What are the functions of the CT
Differ according to type of CT and its components generally: Structural support Medium for exchange Aiding in defense and protection Forming site of storage of fat
How are CT cells classified
Fixed: resident population of cells that have developed and remain in place within connective tissue ex: fibroblasts and adipose cells
Transient: free cells originate mainly in bone marrow and circulate in bloodstream where they reach the CT in response to specific signals
Ex: mast cells, macrophages(can become resident) plasma cells lymphocytes,neutrophils,eosinophils, basophils and monocytes
Describe the structure and function of fibroblasts
▪️Most abundant
▪️Function: responsible for synthesis and secretion of extracellular components
▪️Functional forms: active:with protein synthesis machine when cell is actively manufacturing matrix such as in wound healing
Inactive( fibrocytes) smaller and more ovoid with less organelles
Contain actin and myosin filaments resembling smooth muscles
Describe structure and function of adipose cells
Do not undergo cell division
Function: storage and synthesis of triglycerides
Types: unilocular: cells with single lipid droplet and form white adipose tissue
Multilocular:multiple small lipid droplets and form brown adipose tissue
Describe unilocular fat cells
Cont store fat until they enlarge and displace cytoplasm and nucleus peripherally against plasma membrane giving signet ring profile under LM
Describe multilocular fat cells
Smaller and more polygonal than unilocular fat cells
Have more mitochondria
Describe mast cells structurally and functionally
Ovoid and possess a centrally placed spherical nucleus
Characterized by abundant secretory granules that contain different chemical mediators such as heparin histamine and leukotrienes,interlukins and tumor necrosis factor
Function: immune system by initiation of inflammatory response known as immediate hypersensitivity reaction(anaphylactic reaction)
Why is hypersensitivity reaction induced
By foreign antigens such as bee venom pollen and certain drugs
What do mast cells contain instead of heparin in alimentary tract
Mucosa contains chondroitin sulphate
Why does hay fever occur
Dud to effects of histamine being released by mast cells from nasal mucosa
How do asthma attacks occur
Extra release of leukotrienes in lungs which results in difficulty in breathing
Describe macrophages structurally and functionally
Arise from circulating monocytes and they are most abundant phagocytotic cells in CT
Function: Remove cellular debris and protect body against foreign invaders
Structure: large cells with irregular surface that show blunt projections or filopodia reflecting cell motility and abundance of lysosomes reflecting active phagocytosis
Describe plasma cells structurally and functionally
Derived from b lymphocytes and manufacture antibodies
Cytoplasm is intensely basophilic(presence of RER) except in prenuclear area which appears pale and is referred to as a negative Golgi image
What how are WBCs classified
▪️Granulocytes
Neutrophils
Eosinophils
Basophils
▪️Non granulocytes
Lymphocytes
Monocytes
Describe neutrophils
▪️60-70% of total leukocyte population
▪️Multi lobed nucleus held by chromatin
▪️Pale cytoplasm
▪️Barr body in females
Functions:
▪️First line of defense against bacterial infection (phagocytose and destroy bacteria by content of their granules)
▪️Can migrate through blood capillary wall to reach CT sites where there is bacterial infection to act in phagocytosis
▪️After preforming their function: cells die and form pus cells
Describe eosinophils
Bilobed nucleus and eosinophilic granules
Function:phagocytose antigen-antibody complexes and kill parasitic invaders
What inc formation of eosinophils and what dec it
Release of histamine and IL-5 from CT cells in vicinity of antigen antibody complexes
Elevation of blood corticosteroid levels dec number of eosinophils
Describe basophils
Characterized by s shaped nucleus and abundant basophilic granules in cytoplasm
Function: meditate allergic and inflammatory reaction through release of granules content such as histamine and heparin
What is anaphylactic shock and how does it happen
It occurs due to a second exposure of same allergen resulting in an intense generalized response
Large number of basophils and mast cells degranulate and result in widespread vasodilation and sweeping reduction in blood volume and person goes in to circulatory shock
Smooth muscles of the bronchial tree constrict causing respiratory insufficiency
Describe monocytes
Largest wbcs
Kidney shaped nucleus
Irregular surface with projection from cell membrane
Possess abundant lysosomes
Migrate in to CT and become macrophages
Phagocytose and destroy dead and defunct cells as well as antigens and foreign particulate matter (occurs within phagosomes)
Functions of monocytes
Phagocytose unwanted material
Produce cytokines that are required for anti inflammatory and immune responses
Present epitopes to t lymphocytes thus acting as antigen presenting cells to elicit and immune response
Describe lymphocytes
Rounded cells round big nucleus
B(15%)
T(80%)
Null cells(5%)
Function of lymphocytes
No function in blood stream but in CT they are responsible for proper functioning of immune system
B cells mature and leave bone marrow as mature b cells
T cells migrate to thymus where they become mature and immunocompetent
What happens when lymphocytes become immunologically competent
Leave respective sites of maturation and enter lymphoid system and undergo mitosis and form clones
Clones can recognize and respond to same antigen
What do b and t cells proliferate in to
Memory cells and they do not participate in immune response but remain as part of the clone with an immunological memory
Effector cells and are classified as b cells and t cells
What are myofibroblasts
Myofibroblasts:represent transitional modifications of fibroblasts responding to signaling molecules within a regional intercellular matrix as in areas undergoing wound healing
