Cells and Tissues (Histology) PDF

Cells and Tissues (Histology) Goals Describe the structure and function of the cellular organelles associated with the endomembrane system, including the endoplasmic reticulum, Golgi apparatus, and lysosomes Describe the structure and function of mitochondria and peroxisomes...

Cells and Tissues (Histology) Goals Describe the structure and function of the cellular organelles associated with the endomembrane system, including the endoplasmic reticulum, Golgi apparatus, and lysosomes Describe the structure and function of mitochondria and peroxisomes Explain the relationship between organelle populations and cell functions ► This is a generalized cell diagram. It shows the anatomy of a cell, but most cells do not actually look like this. Cell Organelles Organelle Function Cytosol Space-filling plasma with nutrients and wastes Nucleus Contains DNA and protects it from reverse engineering Nucleolus Creates RNA, especially for ribosomes Endoplasmic Manufacturing proteins (rough) or lipids (smooth) and storing Reticulum (Rough and materials (Ca++ especially) Smooth) Golgi Apparatus Sort, modify, and package molecules for transport (vesicles) Ribosome Translates RNA into proteins by linking amino acids Lysosome A vesicle with enzymes for breaking down molecules Mitochondria Creating energy in the form of ATP via Krebs Cycle (requires O2) Cytoskeleton Protein fibers that structure, move organelles, and provide extracellular movement Peroxisome Vesicles with peroxidases and other enzymes to break poisons ► Cells can have a wide variety of shapes and sizes, depending on their function. ► Tissue- cells similar in structure that group to perform common function ► Histology – study of tissues Four Tissue Types ► Nervous ► Muscle ► Epithelial ► Connective Nervous Tissue ► Function – regulate and control body function via electrical impulses ► Neurons – specialized nerve cells ► Neuroglia – supporting cells, which may insulate, protect, or guard  Cortical neuron and stem cells with differing antibody stains Neuron, Commons License, Gerry Muscle Tissue ► Elongated, vascularized cells which contract Voluntary Involuntary ► Skeletal muscle tissue is made of large, cylindrical, multinucleated cells up to a 30cm (1 ft) long. 40 % mass ► The repeating groups of muscle filaments create a series of bands called striations. ► Function: Voluntary movement, locomotion ► Example: All voluntary muscles ► Cardiac muscle ► Involuntary, branching, striated, mostly uninucleate with special junctions (intercalated discs) ► Function: Contracts; found only in the heart, so propels blood into circulation 2013 Pearson Ed, ► Have desmosomes for strong attachments between cells. ► The cells also have gap junctions, which allow ions and electrical impulses to travel quickly between the cytosol of each cell. ► Smooth muscle ► Cells are spindle-shaped, with a wide middle and narrow ends. No striations, arranged in sheets, central nucleus, involuntary ► Function: Contraction (usually of a hollow organ) ► Example: ureter, intestines. Cross Long section section HistologyOLM is authored by Stephen Gallik,  Epithelial Tissue ► 2 main subtypes: covering/lining and glandular ► Epithelial tissue often line a lumen, or inner space of a tubular structure. Epithelial Tissue ► Functions ► Characteristics ► Polarity – an apical ►Protection and a basal surface ►Absorption (usually attached to ►Filtration connective tissue “basement membrane” ► Excretion or lamina) ►Secretion ► Specialized contacts ► Avascular, innervated ►Reception ► High regeneration rate ► Often found in sheets ► Cells in some epithelium are held together by tight junctions; waterproof attachments by membrane proteins. ► Some epithelial cells may held together by desmosomes, which are protein filaments that pass through the cell membranes of neighboring cells. ► This may be in addition to tight junctions, or instead of (if there are gap junctions instead). ► Desmosome junctions are the reason why skin cells often peel off in sheets instead of individually. Functions of Epithelium ► Epithelium provides physical protection of body surfaces from abrasion, dehydration, or chemical destruction. ► Epithelium controls permeability by allowing or preventing substances from entering the body. The skin is impermeable to most substances, including ► Epithelial cells have sensation; the ability to detect changes in the environment and relay those changes to the nervous system. Monofilament sensation test for ► Epithelium cells secrete substances out of the body or into an organ cavity. ► Exocrine glands discharge secretions to surfaces exposed to the outside, such as the lining of the digestive tract or skin. ► Endocrine glands secrete directly into tissue fluid or blood. Classification of Epithelium ► Simple epithelium consists of a thin, single layer of cells covering the basement membrane. ► Found in areas that need to be highly permeable. ► Stratified epithelium has several layers of cells above the basement membrane, creating a greater degree of protection. ► Found in areas that experience a lot of physical abrasion. ► Epithelial cells are also classified by shape: ► Squamous cells are flattened. ► Cuboidal cells are square-shaped. ► Columnar cells are rectangular. ► Simple squamous epithelium allows for diffusion in areas where substances are absorbed or released. ► Examples: Lining of the heart, blood vessels, kidney tubules, air sacs of lungs. Cross-section of alveoli; air sacs within the lungs. ► Simple cuboidal epithelium contains larger, cubelike cells that are able to secrete and absorb more material. ► Examples: Pancreas, salivary glands, urine production areas of kidneys, ovary surface Cross-section of tubules within the kidneys. ► Simple columnar epithelium – single layer, tall cells w/ round/oval nucleus ► Sometimes have cilia; sometimes are goblet cells (mucus secreting, unicellular gland) ► Function: absorption, secretion (mucus, enzymes, other things) ► Examples: Stomach lining, intestinal tract. Projections in the small intestines called ► Pseudostratified (mostly ciliated) columnar epithelium appears layered, but each cell touches the basement membrane. ► Some cells don’t reach surface, nuclei at different layers ► Examples: Lining of the nasal cavity, trachea, and bronchi. Nonciliated often in ducts of large glands and sperm-carrying ducts Trachea. ► The cilia are able to move independently, pushing secreted mucus (and trapped foreign particles) out of the respiratory tract. ► Stratified squamous epithelium - protective layers of cells that are flattened at the apical surface, cuboidal or columnar in deeper layers ► May be keratinized (hardened) or nonkeratinized ► Only alive in the basal layers ► Examples: Lining of the mouth, skin, esophagus, and anus. Epidermis layer of the skin. Stratified Cuboidal Epithelium ► Stratified cuboidal epithelium ► Quite rare; found in some sweat and salivary glands ► Typically only two cell layers thick Stratified Columnar Epethelium ► Limited distribution ► Occurs in transition areas between two other epithelia ► Only apical layer columnar Mammary glands, esophageal glands ► Transitional epithelium forms lining of hollow urinary organs ► Basal cells cuboidal or columnar, flattening when stretched ► Apical cells variable in appearance ► Examples: Urinary bladder. Glandular Epithelium ► Endocrine = ► Exocrine = having ductless ducts ► Secretions travel ► Secretions through blood or released onto lymph to target surfaces or into cavities Merocrine Holocrine (sebaceous) Apocrine ? In humans Connective Tissue ► Connective tissue, unlike epithelium, is never exposed to the outside environment, and has a much more diverse set of functions and properties. ► Four main groups: ► Conective Tissue Proper ► Cartilage ► Bone ► Blood  Functions of Connective Tissues ► Storage (minerals and fuel) ► Protection, Insulation, and Transport ► Binding and Support ► Connective tissues have extracellular matrix of differing types to assist with this function. ► Collagen fibers are the thickest and strongest type of protein fiber found in extracellular matrix. ► Elastic fibers are much thinner, but can stretch and recoil. ► Ground substance is the clear, gel-like substances that cells and other protein fibers are laying in. ► Reticular fibers are also thin, but crosslink with each other to form a mesh-like network. Type 1: Loose Connective Tissues ► Loose connective tissues are the “packing materials” of the body, filling in spaces to provide cushioning and support. ► Areolar tissue contains a mixture of collagen and elastic fibers and multiple cell types. ► Functions ► Strongly and flexibly binds tissues together ► Reservoir of water and salts ► Example: Between the skin and muscle. ► Adipose tissue is made of fat cells, also called adipocytes. ► Function: Energy storage, shock absorption, and thermal insulation. ► Example: Fat storage areas in the skin. ► Reticular tissue is mostly made of reticular fibers holding cells in place. ► Function: Red blood cell, white blood cell “hang-out”. ► Example: Spleen, bone marrow, lymph nodes. Dense Regular Connective Tissues ► Dense regular connective tissues consist mostly of closely packed collagen fibers parallel to direction of pull ► Fibers slightly wavy for a little stretch ► Few cells, almost no blood supply ► Dense connective tissue contains fibroblasts, cells that produce collagen, elastic, or reticular fibers. ► Function: tension resistant connection ► Location: tendons Dense Irregular Connective ► Similar to Regular, but collagen bundles thicker and not parallel ► Resists tension from multiple directions ► Locations: dermis, joint capsules, some organ covers (digestive) Elastic Connective Tissue ► Dense regular, but with more elastic fibers ► Allows tissue recoil ► Found in large arteries, vertebral ligaments, bronchi and bronchioles Cartilage ► Cartilage contains chondroblasts and chondrocytes, cells that produce extracellular matrix and enable fluid exchange within the cartilage. ► Chondrocytes are found within small pits within the matrix called lacunae.  Cartilage ► Tough, but still flexible ► Avascular ► Non-innervated ► Up to 80% water ► Hyaline cartilage contains densely packed collagen fibers and ground substance. ► Function: Smooth surface, flexibility, and support. ► Example: Respiratory tract, connecting ribs to sternum, and covering the ends of bones. ► Elastic cartilage is made of densely- packed elastic fibers. ► Function: Withstand repeated bending while maintaining its original shape. ► Example: External ear, epiglottis ► Fibrocartilage is tightly-packed with thick collagen fibers but has fewer cells. ► Function: Able to resist compression. ► Example: Spinal discs, between bones of pelvis and bones of knee. ► Fibrocartilage looks similar to dense regular tissue, but the cells are in lacunae. Osseous Tissue ► More collagen than cartilage! ► Calcium salts ► Vascularized ► Bone contains concentric circular layers called lamellae. ► Function: Support, structure, movement ► Example: skeleton ► Note: osteon Fluid Connective Tissues ► Blood contains blood cells, platelets, and soluble proteins ► Functions: Transport of nutrients, blood gases, hormones, and defense from disease.