BMS100_PHL101v2 Tissues and Organs PDF

Tissues • Most of these tissues are found in almost every region in the body • Not just in the limited distribution here • i.e. smooth muscle is found in almost every region of the body, as it forms an integral part of blood vessels Epithelial tissue - functions • Protection ▪ Physical, thermal, c...

Tissues • Most of these tissues are found in almost every region in the body • Not just in the limited distribution here • i.e. smooth muscle is found in almost every region of the body, as it forms an integral part of blood vessels Epithelial tissue - functions • Protection ▪ Physical, thermal, chemical ▪ From microbes • Transport ▪ Absorption - water, nutrients, electrolytes… almost anything your GI tract chooses ▪ Secretion or removal of wastes – GI tract, kidney, lung ▪ Optimizing diffusion – thin cells that reduce the distance substances need to diffuse – endothelial cells, alveolar cells • Secretion of useful substances ▪ i.e. mucous, other glandular secretions, hormones Epithelium - membranes • Most membranes in the body are epithelial membranes ▪ Epithelium faces a cavity, tube, or the outside world ▪ Underlying connective tissue anchors and nourishes the overlying epithelium ▪ Epithelial membranes are important components of several organs and organ systems • Gastrointestinal, urinary, respiratory, cutaneous, cardiovascular, reproductive • Connective tissue membranes have no epithelial lining ▪ Cover an organ (i.e. a capsule) ▪ Line a joint (i.e. knee, shoulder joint) Epithelial membranes • Often a membrane can perform the same overall function in multiple different ways • Examples • Two ways the skin protects? • Two ways the respiratory membrane keeps “stuff” out of gas exchange areas? Connective tissue Very broad set of forms and functions • Structural and protective functions ▪ “Stronger structures” • bone, cartilage • dense regular (tendons, ligaments) • dense irregular tissue (dermis of the skin) ▪ “Weaker structures” • Areolar and reticular (lymph nodes, thymus, spleen) • Adipose tissue (fat) Connective tissue Very broad set of forms and functions • Specialized functions ▪ Fluid connective tissue • Red blood cells, platelets → functions? • Lymph → functions? • Cells of the immune system (leukocytes) → functions? ▪ “Other” • Bone is an important endocrine organ and mineral storage depot • Fat is an important endocrine organ, store of metabolic energy, and thermoregulator “Structural” connective tissues • Cells ▪ Fibroblasts, osteoblasts/osteocytes, chondroblasts ▪ Adipocytes, mesenchymal cells • Matrix ▪ Fibres (not in fluid connective tissues) • Collagen(s) • Elastic fibres • Reticular fibres ▪ Ground substance • Polysaccharide and protein complexes for most connective tissue (more later) Generalized connective tissue – Connective Tissue Proper • Includes loose and dense connective • Bone and cartilage are not considered connective tissue proper • Bone has a very specialized matrix, as does cartilage • Cartilage has very few cells and little blood supply • No adipocytes in either bone or cartilage Connective Tissue Proper Cells + Matrix • Fibres – proteins that are responsible for the structural characteristics of connective tissue: ▪ Collagen – different types have different functions • Type I – very strong, cable-like protein that imparts strength • Type IV – more delicate that often links epithelial tissue to connective tissue (remember membranes)? ▪ Elastic fibres are responsible for tissue and organ elasticity Connective Tissue Proper Cells + Matrix • Ground substance ▪ Can be simple globular proteins (glycoproteins) ▪ Can be huge “brush-like” aggregates of proteins and large polysaccharides known as proteoglycans ▪ Both are “surrounded” by water Glycoproteins and Proteoglycans Connective Tissue Proper Cells + Matrix • Fibroblasts – produce the matrix • Macrophages – immune cells that have a diverse set of functions in repair and defence • Adipocytes – a cell with a central large fat-storing vacuole Muscle tissue Specialized cytoskeleton that allows the cell to shorten and exert a pulling force with a variable expenditure of ATP • Skeletal ▪ Voluntary, responsible for movement (musculoskeletal system) ▪ Striated fibres with a very orderly cytoskeletal arrangement • Cardiac ▪ Involuntary, only found in the heart, pumps blood ▪ Similar cytoskeletal arrangement as skeletal muscle • Smooth ▪ Involuntary, found in a wide variety of organs (therefore wide variety of functions) ▪ Less order to the cytoskeleton, lower ATP expenditure Muscle Tissue • Skeletal • Smooth • Cardiac Nervous tissue Much greater detail to come as the semester progresses – for now: 1. The peripheral nervous system detects a stimulus and relays it to the central nervous system (sensory) 2. The central nervous system (brain, spinal cord) integrates this information → a response 3. The response is carried to effectors (muscles, glands, blood vessels) via the peripheral nervous system (motor) Nervous tissue The cells of the nervous system include: • Neurons – an excitable cell that: ▪ receives a stimulus from a neuron or a receptor • dendrites ▪ integrates it (ranks it, compares it to other stimuli) • Cell body, axon hillock ▪ Passes along another stimulus if it is adequately stimulated • axon Nervous tissue • Axons are carried in bundles ▪ Nerves in the peripheral system ▪ Tracts in the central nervous system • Most neuronal cell bodies reside in the CNS, with a few exceptions: ▪ Dorsal root ganglia – neuronal cell bodies for the axons that bring most sensory information from the PNS to the CNS ▪ Autonomic ganglia – help regulate the activities of the autonomic nervous system ▪ Enteric ganglia – help regulate the activity of the gut Nervous tissue The cells of the nervous system include: • Glial cells ▪ Astrocytes – support neurons within the central nervous system ▪ Oligodendrocytes – “insulate” axons with a layer of myelin within the central nervous system ▪ Schwann cells –myelinate axons in the peripheral ▪ Microglial cells – clean up debris, detect microbial nervous system invaders/injury in the peripheral nervous system The Organ Level of Organization • Organs are: ▪ Built from multiple types of tissues (usually all four) ▪ Perform a specific set of functions ▪ Work together with other organs (often with very different combinations of tissues) as an organ system • All organs in a system have similar or related (or both) sets of functions • Example – the heart ▪ Tissues? ▪ What organ system? Other organs? ▪ What’s the function of the heart? The function of the system? The Heart and Cardiovascular System Tissues of the heart? Other organs in the system? Organ System Challenge The subsequent slides have tables that list the organ systems and their “primary” (i.e. well-known) functions • Match as many “additional” functions as you can to the cells in the table in the next 8 minutes • Vitamin D production • Endocrine – RBC production • Acid-base balance • Electrolyte balance • Mineral balance • Thermoregulation • Tissue repair • Control of the endocrine system • Growth • Blood sugar regulation • Vitamin storage • Removal of wastes • Destruction of cancer cells Some will be duplicated The Organ Systems System Primary Functions Additional Functions? Integumentary Protection Sensation Skeletal Protection Support Movement Muscular Movement Nervous Detects and processes sensory information → responses Endocrine Secretes hormones that impact metabolism, activity, and growth of most organs/systems The Organ Systems System Primary Functions Cardiovascular Delivery of nutrients and oxygen to tissues Removal of wastes Lymphatic and Protection from microbes Immune Respiratory Oxygenates blood and removes carbon dioxide Digestive Processes food and removes undigested wastes Urinary Water balance Waste removal Reproductive Produces gametes Supports embryo/fetus Additional Functions? Physical Exam Findings Reflect “Lower” Level Function and Dysfunction • If a focused physical exam assesses one or a few organ systems, then why do we need to think at the tissue or cellular level during the physical exam? ▪ Most disease is due to dysfunction at the molecular, cellular, or tissue level • It explains and often predicts findings at the macroscopic level ▪ When a disease affects multiple systems, the explanation for the physical exam findings is often best understood at these lower levels Physical Exam Findings Reflect “Lower” Level Function and Dysfunction • For example – fatigue due to anemia ▪ The physical exam will not directly detect a decrease in the red blood cell count ▪ It may detect: • An increased heart rate: less RBCs → lower oxygencarrying capacity → need for an increase in blood flow globally to the body → heart rate increases, delivering more RBCs/minute • Rapid respiratory rate • Turbulent flow within the heart due to increased cardiac output → physiologic murmur • Pallor of the conjunctiva • Jaundice or scleral icterus (yellowing of the sclera or skin) if the anemia is due to destruction of red blood cells ▪ The yellow pigment is due to hemoglobin breakdown products Physical Exam Findings Reflect “Lower” Level Function and Dysfunction • In the example of anemia: ▪ The findings during the physical exam (assessing organs/systems) were best understood and explained at a molecular, cellular or tissue level • Reduced tissue oxygenation • Breakdown products of RBCs ▪ When findings across systems are consistent with one or a few causative factors, this can help establish a diagnosis or suggest further confirmatory tests • Adaptation of multiple organ systems to a cellular → tissue problem