Compléter FUNBIO 14 PART 2Version en ligne Different Types of Covering and Lining Epithelium: Shapes of cells 1- Squamous a) Thin cells, arranged like floor tiles b) Allows for rapid passage of substances 2- Cuboidal a) As tall as they are wide, shaped like cubes or hexagons b) May have microvilli c) Function in secretion or absorption 3- Columnar a) Much taller than they are wide, like columns b) May have cilia or microvilli c) Specialized function for secretion and absorption 4- Transitional a) Cells change shape, transition for squamous to cuboidal and back b) Organs such as urinary bladder stretch to larger size and collapse to a smaller size The function of glandular epithelium is secretion A gland may be a single cell (e.g. goblet cells which secrete mucus) or a group of cells that secrete substance into tubes (‘ducts’) Glands classified as Exocrine: secrete into ducts that empty onto surface of a covering and lining epithelium (e.g. skin or lumen of hollow organ such as stomach) Endocrine: No ducts. Secretions are called hormones; enter interstitial fluid and then diffuse into blood stream par Zainab Nabeel 1 Different Types of Covering and Lining Epithelium : Shapes of cells 1 - a ) Thin cells , arranged like floor tiles b ) Allows for rapid passage of substances 2 - a ) As tall as they are wide , shaped like cubes or hexagons b ) May have microvilli c ) Function in secretion or absorption 3 - Columnar a ) Much taller than they are wide , like columns b ) May have or microvilli c ) Specialized function for secretion and absorption 4 - Transitional a ) Cells change shape , transition for squamous to cuboidal and back b ) Organs such as urinary bladder stretch to larger size and collapse to a smaller size The function of glandular epithelium is secretion A gland may be a single cell ( e . g . goblet cells which secrete mucus ) or a group of cells that secrete substance into tubes ( ? ducts ? ) Glands classified as : - Exocrine : secrete into ducts that empty onto surface of a covering and lining epithelium ( e . g . skin or lumen of hollow organ such as stomach ) - Endocrine : No . Secretions are called hormones ; enter interstitial fluid and then diffuse into blood stream connective tissue : One of most abundant and widely distributed tissues in body ( but not usually found on body surfaces ) Highly ( except cartilage ? avascular ; and tendons ? scanty blood supply ) Variety of functions including - bind cells and organs of the body together - protect and internal organs - structures ( e . g . skeletal muscle ) - serve as major transport systems in the body ( e . g . blood ) - are primary locations of stored energy reserves ( e . g . adipose / fat tissue ) - are main sources of immune responses All connective tissues consist of two basic components : 1 . Cells 2 . Extracellular Material ( At least ) two types of connective tissue are found in the body : Connective tissue Specialized connective tissue connective tissue cells : - Fibroblasts Secrete and components of ground substance - Adipocytes ( fat cells ) Store triglycerides ( fat ) - Mast cells Produce histamine - White blood cells Immune response Neutrophil and - Macrophages Engulf bacteria and cellular debris by - Plasma cells Secrete antibodies Ground substance : - Between cells and fibers ( Fluid , semifluid , gelatinous , or calcified ) - Functions to support and bind cells , store water , and allow exchange between blood and cells - Complex combination of proteins and polysaccharides Fibers : - Function to strengthen and support connective tissues - Three types : Collagen fibers , Elastic fibers , and fibers Connective tissue proper is an important structural component of organs . Consists of two types : - Loose connective tissue ( loose network of fibers , with cells in - between ) E . g . , adipose and reticular connective tissue - Dense connective tissue ( densely packed fibers , interspersed with cells in - between ) E . g . dense regular , dense irregular , elastic connective tissue Specialized connective tissues perform specific functions essential to . Three types : Cartilage , Bone , Liquid ( Blood & lymph ) loose connective tissue : areolar connective tissue - Most widely distributed in the body ( " packing material " of body ) - Contains several types of cells and all three fibers Loose Connective Tissue : Adipose Tissue - Contains adipocytes - Good for insulation and energy reserves - White ( common ) and brown adipose tissue Loose Connective Tissue : Reticular Connective Tissue - Fine interlacing reticular fibers and cells - Forms the ( supporting framework ) of liver , spleen , and lymph nodes Reticular fibres or reticulin is a type of fibre in connective tissue composed of type III collagen secreted by reticular cells . Reticular fibers crosslink to form a fine meshwork ( reticulin ) Dense Connective Tissue : Dense Connective Tissue - Bundles of collagen fibers are regularly arranged in parallel patterns for strength - Form Tendons and most ligaments ( attachment and withstands tension ) Dense Connective Tissue : Dense Connective Tissue - Collagen fibers are usually irregularly arranged - E . g . Dermis of skin , of heart , periosteum of bone - Found where pulling forces are in many directions Dense Connective Tissue : Elastic Connective Tissue - Contain branching elastic fibers with between fibres - Strong and can recoil to original shape after stretching - Lung tissue , walls of arteries
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