BIOL1110 M2 Lecture 4 PDF - Tissues and Organs

BIOL1110 From Molecules to Cells (Lecture 4) Tissues and Organs Dr. Gary Ying Wai Chan Office: Rm4N11 KBSB Email: [email protected] ample 1: Phenotype of claudin-1 knockout mice Wild type Claudin-1 KO Impairment of the epidermal bar...

BIOL1110 From Molecules to Cells (Lecture 4) Tissues and Organs Dr. Gary Ying Wai Chan Office: Rm4N11 KBSB Email: [email protected] ample 1: Phenotype of claudin-1 knockout mice Wild type Claudin-1 KO Impairment of the epidermal barrier in claudin-1–deficient mice. (A) 12-hr-old claudin- 1+/+, claudin-1+/-, and claudin-1-/- mice. Claudin-1-/- mice were characterized by wrinkled skin and died within 1 d of birth. (B) Dehydration assay. After claudin-1+/- intercross littermates obtained by Caesarian section at embryonic day 18.5 were resuscitated, their weights were monitored hourly without feeding. Severe water loss from skin  death  Example 2: Acid secretion by parietal cells Parietal cells deep in the gastric glands secrete hydrochloric acid into the lumen of the stomach. Acid secretion in the stomach averages 1-3 liters per day and can create a luminal pH as low as 1. The cytoplasmic pH of the parietal cells is about 7.2, which means the cells are pumping H+ against a gradient that is 2.5 million times more concentrated in the lumen. (1) Hydrogen ions are formed from the dissociation of water molecules. (2) The process begins when H+ from water inside the parietal cell is pumped into the stomach lumen by an H+/K+ ATPase in exchange for K+ entering the cell. The enzyme hydrogen potassium ATPase (H+/K+ ATPase) is unique to the parietal cells (3) Cl- then follows H+ through an open chloride channel, resulting in net secretion of HCl by the cell. (4) While acid is being secreted into the lumen, bicarbonate made from CO2 and the OH- from water. This is catalyzed by the carbonic anhydrase (CA). (5) The bicarbonate ion (HCO3-) is exchanged for a chloride ion (Cl-) on the basal side of the cell and the bicarbonate diffuses into the venous blood. The tight junctions are found in between the cells to make sure no back pass of the ions. Overall, a net in flow of H+ and Cl (HCl) into the lumen of stomach.  Cells stick to each other to form tissue and organ SmallestCell unit that Structural unit of Structural unit of Tissue Organ lives and certain types and an organism that and organ reproduces on system its proportion of adapts for a own cells that special function interacts one another Example (simplified) Nerve cell Nervous tissue Heart + Neuroglial cell + Epithelial tissue + Cardiac muscle tissue + Connective tissue (blood) Four basic tissue types: 1. Epithelial tissue 3. Muscle tissue 2. Connective tissue 4. Nervous tissue Epithelial tissue  Epithelial tissue consists of cells fitted tightly together to form a continuous layer of cells with surface facing the outside environment or body fluid  Perform many functions such as protection (epidermis), absorption (digestion tract) and secretion (gland) Different forms of epithelial tissue Blood vessel kidney GI skin respiratory Stratified Pseudostratifi Squamous Cuboidal Columnar squamous ed epithelium epithelium epithelium epithelium epithelium  Different forms of epithelial 1. Blood vessel tissue2. kidney 3. Gastrointestinal (GI) tract Squamous epithelium: Cuboidal epithelium: Columnar epithelium: cells are flat and arranged Single layer of cells, cross- Single layer of cells enclosed as single layer. It gives a section from tubules, from with secretory vesicles (in smooth, low-friction the side each cell looks like goblet cells), highly surface. E.g., air sacs of a short cylinder, specialized developed Golgi, for lung, lining of blood for diffusion and absorption and secretion of vessels absorption. E.g., lining of enzymes. Lining of GI tract kidneys 4. Skin 5. Respiratory passages Ciliated pseudostratified Stratified squamous epithelium: Ciliated, mucus- epithelium: several layers secreting, cells are columnar of cells with the only lower but are not at the same height, ones columnar and but they are all attached to metabolically active, upper same basement membrane; layers of died cells. part of respiratory passages Connective tissue - Widely distribute in our body, found in between other tissues. - Range from soft connective tissue to specialized types (e.g., blood) - Cells in connective tissue except blood are able to secrete ECM - Cell secretes different types of collagens and modified polysaccharides e.g., Cartilage cells (chrondrocytes)  collagen II and proteoglycan Bone cells (osteoblasts)  tough fibers (collagen I) and calcium phosphate Soft connective tissue Specialized connective tissue Muscle tissue - Is specialized for contraction - Three types: Skeletal, cardiac, smooth Nervous tissue Is found everywhere in our body (brain, spinal cord and nerves) Is specialized for receiving and transmitting signals Consists of neurons and glial cells Neurons are the basic units of communication in nervous tissue Nervous tissue comprises glial cells that support and protect neurons Dendrites receive signals Axon (