Simple Squamous Epithelium

Transcription

1 Histology

2 Simple Squamous Epithelium One layer of flattened cells. Protective characteristics are diminished because of this. Examples: Alveoli in the lungs Capillaries where diffusion of nutrients and waste occurs.

3 Stratified Squamous Epithelium Many layers, cells flattened at the surface. Plays a protective role. Non-keratinized cells lines moist surfaces near open body orifices such as the mouth, vagina and anus. Keratinized cells make up the outer surfaces of skin cells. Basal cells produce cells with little keratin but they develop more as they rise to the surface and die. Keratin is a fibrous protein that protects epithelial tissue from damage and stress.

4 Simple Cuboidal Epithelium One layer of cube-shaped cells. Contain many mitochondria to assist tubules in the kidneys where urine is formed to absorb substances from the tubule and secrete substances into the tubule. Also found in glands like salivary, thyroid, and the pancreas where its function is secretion. Stratified cuboidal epithelium is found mostly lining larger ducts of certain glands like mammary glands and salivary glands. It often composed of two layers.

5 Simple Columnar Epithelium One layer of cells that are longer than they are wide. They form goblet cells that secrete mucous onto the free surface of the epithelium. Lining of digestive organs like the small intestine to help absorb products of digestion. Cilia on these cells in uterine tubes help move the egg toward the uterus or womb.

6 Pseudostratified columnar epithelium One layer of elongated, tapered cells that appear stratified. Nucleus is at the wide end of the cell. See picture for location and function.

7 Connective Tissue Binds structures together, provides support and protection, fills spaces, produces blood cells and stores fact. Three fibers found in the matrix of connective tissue: Collagen fibers are made of a protein called collagen that gives them flexibility and strength. Elastic fibers contain the protein elastin which aren t very strong but are stretchy. Reticular fibers are very thin, highly branched, collagenous fibers form supporting networks.

8 Adipose-Loose Connective Tissue Fibroblasts are a cell in connective tissue that produces collagen and other fibers. In adipose, fibroblasts enlarge and store fat. They have little extracellular matrix It protects and cushions many organs like the eye, kidney, and is found beneath the skin. It stores energy and provides insulation against the cold.

9 Dense Connective Tissue Dense connective tissue has a matrix produced by fibroblasts that contains thick bundles of collagen fibers. Three types of regular dense connective tissue include: Bundles are parallel as in tendons (which connect muscles to bones), Ligaments (which connect bones to other bones at joints) are also parallel. Aponeuroses (sing., aponeurosis; which join muscle to muscle) are also parallel. In dense irregular connective tissue, the bundles run in different directions. This stretchy tissue is found in the inner portion of the skin (called the dermis) and in joint capsules.

10 Cartilage Cartilage is made of cells called chondrocytes. Three types: Hyaline is the most common. It is strong yet flexible. Found in the nose, at the ends of long bones and ribs, and in the supporting rings of the trachea. Elastic is more flexible. Found in the outer ear. Fibrocartilage absorbs shock and can withstand tension and pressure. Found in disks between the vertebrate in the backbone and the pads of knee joints.

11 Cartilage

12 Bone Most rigid of the connective tissues. Bone is made of two types of cells, osteoblasts and osteocytes, form an extremely hard matrix of mineral salts, notably calcium salts. Compact bone consists of many cylindrical-shaped units called osteons, or Haversian systems. Spongy bone contain bars and plates called trabeculae separated by spaces. It is still very strong and is used to support places in bone with high stress. Blood cells formed within red marrow are found in spongy bone at the ends of long bone.

13 Bone

14 Blood Blood is a connective tissue composed of formed elements suspended in a piqued matrix called plasma. Rate of cell division is high. Blood cells have a short life span so stem cells in red bone marrow made them constantly. There are three types of formed elements: red blood cells (erythrocytes), which carry oxygen white blood cells (leukocytes), which aid in fighting infection platelets (thrombocytes), which are important to the initiation of blood clotting. Platelets are not complete cells; rather, they are fragments of giant cells called megakaryocytes, which are found in the bone marrow.

15 Muscular tissue Composed of cells called muscle fibers. Fibers contain actin and myosin which are protein filaments whose interaction accounts for movement. 3 types Skeletal Smooth Cardiac

16 Skeletal Muscle Tissue Voluntary muscle. Attached by tendons to the bones of the skeleton or to the skin. Muscle shortens when skeletal muscle contracts causing body parts to move. Ex. Arms and legs Fibers are cylindrical and long, sometimes they span the length of the whole muscle. They have a striated appearance with the nucleus just inside the cell membrane.

17 Smooth (visceral) Muscle Tissue Involuntary, contraction controlled by nervous system. The arrangement of actin and myosin does not give the appearance of crossstriations. Spindle-shaped cells form layers in which the thick middle portion of the cells is opposite to the thin ends of adjacent cells. Nuclei are found in irregular patterns. Found in walls of hollow structures and organs

18 Cardiac Muscle Tissue Involuntary Found only in the walls of the heart. Striated, Single centrally placed nucleus. Contraction is rhythmical and controlled by the nervous system. Intercalated discs are folded plasma membranes between two cells containing adhesion and gap junctions. They make it so the muscle can expand and contract quickly.

19 Nervous Tissue Found in the brain and spinal cord. Made of specialized cells called neurons. Three parts: Dendrite (branches) receives signals that may result in a nerve impulse. Cell body contains the nucleus and most of the cytoplasm. Axons conduct electrical impulses. Axons are called fibers. In the brain and spinal cord fibers form tracts. Outside the brain fibers are bound together by connective tissue to form nerves. Nerves conduct impulses from sense organs to the spinal cord and brain, where sensation occurs. They also conduct signals away to the muscles, glands and organs.

20 Neuroglia Nervous tissue also contains neuroglia. Outnumber neurons 9 to 1. Function is to support and nourish neurons. Types include: Microglia that engulf bacteria and cellular debris. Astrocytes that provide nutrients to neurons and produce a hormone that may help cure Parkinson s disease. Oligodendrocytes that make myelin, a protective layer of fatty insulation. Ependymal cells which line hollow cavities, or ventricles, of the brain. Schwann cells are the type of neuroglia that enclose all long nerve fibers located outside the brain or spinal cord. Only cover a small section of nerve fiber. Gaps between them are called nodes of Ranvier. Collectively they are called the myelin sheath (causing nerves to appear white) which speeds up the nerve impulses by jumping from node to node.

21 Extracellular Junctions Tight Junction-forms an impermeable barrier because adjacent plasma membrane proteins actually join, producing a zipper-like fastener. Digestive juices in the stomach and urine in the kidney tubules stay in because of tight junctions. Adhesion junctions-the adjacent plasma membranes do not touch but are held together by extracellular filaments firmly attached to cytoplasmic plaques made of dense protein. Gap Junctions form when two adjacent plasma membrane channels join. Examples would be found in the smooth muscle of the heart to help with synchronized contraction. These are found in places where a lot of contraction of the tissue happens so tearing doesn t happen. Heart muscle and the cervix during child birth.

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23 Composed primarily of epithelium. Secretions exit through exocytosis, mostly. Endocrine glands no longer have ducts. Mostly produce hormones to help with homeostasis. Examples include, thyroid, pituitary, and others as pictured. Exocrine glands include sweat glands, mammary glands, and the pancreas.

24 Membranes-mucous, synovial, meninges, cutaneous Line the organs, openings to the outside of the body, and the linings of cavities discussed on pages 6-8. Mucous membranes line the interior walls of organs and tubes that open to the outside like those in the digestive, respiratory, urinary, and reproductive system. They usually are made of epithelium and connective tissue and have goblet cells. Examples include the stomach, nose and mouth, especially during sickness. Synovial membranes keep joints and the end of bones connected to them lubricated. They are made mostly of connective tissue. A disorder of this is rheumatoid arthritis. Meninges are membranes found within the posterior cavity that acts as a protective covering for the brain and spinal cord. A disorder of this type of membrane would be meningitis. Cutaneous membrane-forms the outer covering of the body. Consists of keratinized stratified squamous epithelium.

25 Serous Membranes Serous membranes line cavities like the thoracic and the abdominopelvic cavities. They also cover internal organs such as intestines. Thorax-pleurae are serous membranes that form a double layer around the lungs. Parietal pleurae lines the thoracic cavity. Visceral pleurae covers the lungs. Excretes serous fluid to protect membranes from infection and to keep them lubricated. 2 types: Parietal refers to walls of cavities. Visceral refers to covering organs. Pericardium is a double layer covering for the heart. Peritoneum is found in the abdomen. Parietal peritoneum lines the abdominopelvic cavity while the visceral peritoneum covers the stomach and other organs in the cavity.