Lesson 2 Chapter 3 – Tissues

Lesson 2 Chapter 3 – Tissues 1 Unit 1 Study Guide Excluded from study: Embryology summary – page 82 – 85 Tissue A tissue is a group of cells that have a similar shape and function. In tissues the simplest combination is called a membrane, or a sheet of tissues which cover or line the body surface or divide organs into parts. Examples include the mucous membrane which lines body cavities. Tissues combine to form organs. An organ is a part of the body which performs a definite function. The final units of organization in the body are called systems. A system is a group of organs each of which contributes its share to the function of the body as a whole. There are 4 main types of basic tissues; epithelial, connective, muscle, and nerve tissues. Epithelial tissue covers the body surface and forms the lining for most internal cavities. The major function of epithelial includes protection, secretion, absorption, and filtration. The skin is an organ made up of epithelial tissue which protects the body from dust, dirt, bacteria, and other microbes. Cells can be flat, thin to cubic to elongated. Connective tissue is the most abundant and the most widely distributed of the tissues. Connective tissues perform a variety of functions including support and protection. The following tissues are found in the human body, ordinary loose connective tissue, fat tissue, dense fibrous tissue, cartilage, bone, blood, and lymph, which are all considered connective tissue. Muscle tissue There are three types of muscle tissue: skeletal (voluntary), smooth (involuntary), and cardiac (involuntary). Skeletal muscle is a voluntary type of muscle tissue that is used in the contraction of skeletal parts. Smooth muscle is found in the walls of internal organs and blood vessels. It is an involuntary type. The cardiac muscle is found only in the walls of the heart and is involuntary in nature. Nerve tissue is composed of specialized cells which not only receive stimuli but also conduct impulses to and from all parts of the body. Nerve cells or neurons are long and string-like. Lesson 2 Chapter 3 – Tissues 2 Continued: Epithelial tissue Epithelial is made of cells arranged in a continuous sheet with one or more layers, has apical & basal surfaces. Well innervated (nerv=nerves) Covers all exposed surfaces, lines internal passages, hollow organs, cavities and duct. Forms glands. Examples: skin, lining of esophagus, lining of bladder, lining of blood vessels, lining of cornea, mammary glands o A basement membrane is the attachment between the basal surface of the cell & the underlying connective tissue. o Two types of epithelial tissues: (1) Covering & lining epithelia and (2) Glandular Epithelium. o The number of cell layers & the shape of the cells in the top layer can classify epithelium.  Simple Epithelium - one cell layer  Stratified epithelium - two or more cell layers  Pseudostratified Columnar Epithelium - When cells of an epithelial tissue are all anchored to the basement Membrane but not all cells reach the apical surface.  Grandular Epithelium – (1) Endocrine: releases hormones directly into the blood stream and (2) Exocrine: secrete into ducts Lesson 2 Chapter 3 – Tissues 3 Continued: Connective Tissues Connective: contains many different cell types including: fibroblasts, macrophages, mast cells, and adipocytes. Connective Tissue Matrix is made of two materials: ground substance proteins and polysaccharides, fiber – reticular, collagen and elastic. It is located throughout the whole body. Classification of Connective Tissue: o Loose Connective - fibers & many cell types in gelatinous matrix, found in skin, & surrounding blood vessels, nerves, and organs. o Dense Connective - Bundles of parallel collagen fibers& fibroblasts, found in tendons& ligaments. o Cartilage - Cartilage is made of collagen & elastin fibers embedded in a matrix glycoprotein & cells called chondrocytes, which was found in small spaces. o Fibrous Cartilage - Strongest type, has dense collagen & little matrix, found in pelvis, skull & vertebral discs. Fixed cells vs Wandering cells o Fixed cell: A relatively immotile macrophage found in connective tissue, lymph nodes, spleen, and bone marrow. - Fibroblasts, Macrophages, Adipocytes, Mesenchymal cells, Melanocytes o Wandering cell: A cell such as a leukocyte, having ameboid movements, with a power of locomotion. - Mast cells, Lymphocytes, Plasma cells, Microphages Lesson 2 Chapter 3 – Tissues 4 Membranes a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ. Consist of epithelial layer over a connective tissue layer. Mucous Membrane Mucous membranes, also called mucosa, line the inside of cavities that open directly to the exterior environment. Mucous membranes line the gastrointestinal tract, respiratory tract, reproductive tracts and the urinary tract. This type of membrane is composed of an epithelial cell layer and an underlying connective tissue layer. The epithelial layer is an important defense mechanism that prevents the entry of pathogens and microbes into the body. The cells are tightly packed together, so fluid cannot leak through the epithelial layer. Specialized cells secrete mucous to keep the membrane moist. Mucous also traps dust particles in the respiratory, or lung passage ways and lubricates food as it travels through the intestinal tract. The connective tissue component of a mucous membrane stabilizes the membrane against the structure it is protecting; it also holds blood vessels that supply blood and nutrients to the epithelial layer in place. Serous Membrane Serous membranes, or serosa, line cavities of the body that do not open directly to the external environment; it also covers the organs within the cavities. For example, this type of membrane lines the chest and abdominal cavities, in addition to covering the liver, spleen, kidneys, heart etc. Serous membranes are made of two layers: a layer to line a cavity, called the parietal membrane, and a layer to cover an organ, called the visceral layer. Serous membranes secrete a lubricant called serous fluid that allows the organs to glide against other structures without causing friction. Cutaneous Membrane The cutaneous membrane, also known as the skin, covers the entire body. It is composed of many layers of epithelial cells to protect the body from invading microbes or pathogens, in addition to light, heat and injury. The skin is the largest organ of the body that also stores fat, vitamin D and water and houses the sensory receptors for touch and pain. It regulates body temperature by secreting sweat to dissipate heat. Synovial Membrane The junction where two bones meet is called a joint. Surrounding freely movable joints like the shoulder, elbow, or knee is a synovial membrane. The synovial membrane secretes synovial fluid to lubricate the joint space, making motion much easier. The synovial fluid also nourishes the cartilage attached to the ends of bones and contains immune cells called macrophages that rid the joint space of invading microbes and debris. Lesson 2 Chapter 3 – Tissues 5 (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) (a) C onnective tissue (b) Squamous (c) Skin Lesson 2 Chapter 3 – Tissues (d) Joints Continued: Muscles Muscle: is divided into 3 categories, skeletal, cardiac and smooth. 1. Skeletal muscle tissue  Long multinucleated cells  Striated (actin and myosin in parallel so muscle appears to have bands across it)  Large skeletal muscles under voluntary nervous system control (usually) 2. Cardiac muscle tissue  Smaller cells with only one nucleus  Also striated  Not under nervous system control, heart has own pacemaker (involuntary muscle) 3. Smooth muscle tissue  Small cells with one nucleus  Not striated as actin and myosin are organized differently  Generally not under voluntary control  Surround hollow organs and passageways to exterior (resp tract, digestive tract, etc) 6 Lesson 2 Chapter 3 – Tissues 7 Continued: Neural Tissue Made up of cells called neurons. Neurons are cells that convert stimuli into electrical impulses to the brain. Located throughout the whole body. Nervous: Consists of only two cell types in the central nervous system (CNS) & peripheral nervous system (PNS): Neurons – are made up of cell body, axon and dendrites. There are 3 types of neurons:    Motor Neuron: carry impulses from CNS to muscles and glands. Interneuron: interpret input from sensory neurons and end responses to motor neurons Sensory Neuron: receive information from environment and transmit to CNS.