Bio. 2304 - Human Anatomy HISTOLOGY (STUDY OF TISSUES) - Lab & Lecture Objectives Important: For each slide know 1.) specific tissue type 2.) any specialized structures or cells in the tissue (& know their functions) 3.) tissue locations 4.) tissue functions. Don t forget that cells are mainly composed of water and are very translucent! Turn down the light to see more detail! Look at each slide under the indicated magnifications; l. p. = low power; h. p. = high power Make drawings of each tissue type. Make sure that you bring some colored pencils to this lab! I. EPITHELIAL TISSUE - covers body surfaces (internal and external); lines body cavities & tubes; forms glands. Note: Epithelial tissue can be classified on the basis of the arrangement of the cells: simple (one cell layer thick), stratified (more than one cell layer thick), or pseudostratified (cells are staggered giving the false appearance of being stratified). Characteristics of epithelium: cells fit closely together cells are attached to an adhesive basement membrane (glycoproteins and connective tissue) the tissue is avascular (no blood supply it receives nutrients by diffusion from blood vessels in the underlying connective tissue). cells can have microvilli or cilia on their surfaces. tissue has high regenerative ability Endothelium (inner covering) epithelium that provides a slick lining in lymphatic vessels, blood vessels, and heart. Mesothelium (middle covering) epithelium found in serous membranes lining the ventral body cavity and covering its organs; also called a serous membrane or serosa. A. Squamous Epithelium 1. Simple Squamous Epithelium Description: flat, scalelike, irregularly shaped cells (like fried eggs) Location: air sacs of lungs; nephrons of kidney; lining of circulatory system, lymphatic vessels, & ventral body cavity Fxns: diffusion (gas exchange) in lungs, filtration in kidneys (why cells are so thin) Slide: Mammal Lung Sec. 31-5648 (H2460) (l.p.); be careful not to confuse with adipose tissue 2. Stratified Squamous Epithelium Description: composed of many layers of squamous epithelial cells Location: nonkeratinized type in moist linings of the esophagus, mouth, & vagina; keratinized type forms the epidermis of the skin (we ll talk more about the protein keratin in the integumentary system) Fxns: protects underlying tissues in areas subjected to abrasion Slides: a. "Stratified Squamous Epithelium Human (H6014)" (l. p.) - look at the outer layer of the tissue section for the strat. squamous cells; this is a slide of the esophagus. b. Squamous Epithelium Smear, Human Mouth (H15) (l.p.) - The squamous epithelial cells in your cheek are stratified, but the cells separated when they made the slide, so you will see individual cells; notice how thin and scalelike they appear; each cell has a small round nucleus.
B. Cuboidal epithelium Description: cube shape; have spherical nuclei Location: kidney tubules, small glands, surface of ovary Fxns: secretion (ex. tears, saliva) & absorption (ex. reabsorption of H 2 O in kidneys) Slide: "Simple Cuboidal Epithelium (93 W3024)" (h. p.) - look at cells lining tubes (large, long spaces) C. Columnar epithelium Description: long, column shaped; oval nuclei; some have cilia (hair-like processes; in respiratory tract, cilia whip up mucous to trap bacteria, etc.); cells in digestive tract have microvilli on surface (folded cell membranes to provide more surface area for absorption); this tissue may also contain mucous secreting goblet cells. Location: nonciliated type lines digestive tract, gall bladder, and excretory ducts of some glands; ciliated type lines respiratory tract and fallopian tubes Fxns: secretion of mucous, enzymes; absorption; ciliated type propels mucous (in the respiratory system) and eggs (in the reproductive system). Slide: "Goblet Cell Epithelium (H215)" (h. p.) - on this slide columnar epithelial cells line the villi of the intestine (fingerlike structures that project in the lumen of the intestine to increase its surface area for more absorption); id. villus, goblet cells (interspersed among the columnar epithelial cells & are white to very light purple in color - if you look closely, you can actually see the mucous coming out of some of the cells), & columnar epithelial cells. II. CONNECTIVE TISSUE - protects & supports the body & its organs, binds organs together, & stores energy reserves. Extracellular matrix is produced by connective tissue cells. Connective tissue cells have different names depending on the type (ex. fibroblasts, chondrocytes, osteocytes, adipocytes, etc.). The matrix is composed of : 1.) ground substance - may be liquid, semisolid, of hard (when hard the cells reside in cavities in the matrix called lacunae); made up of glycoproteins and polysaccharides; matrix supports cells, binds them together, and gives strength & elasticity to tissues; it also holds fluid. 2.) fibers: collagenic (protein collagen, tough, white), elastic (protein elastin, yellow), and reticular (fine, collagenic fibers with a coating of glycoprotein); fibers provide support, strength, and elasticity. A. Loose Connective Tissue (loose arrangement of fibers in the matrix) 1. Areolar ( bubble wrap ) Description: gel-like matrix; contains all 3 fiber types, fibroblasts (produce new fibers & matrix), and white blood cells. Location: under epithelia (ex. lamina propria of mucous membranes) and around organs & capillaries Fxns: like bubble wrap - wraps & cushions organs Slide: "(H105) Areolar Tissue Spread Verhoeff, w.m." (h. p.) 2. Reticular Description: loose ground substance, reticular fibers, fibroblasts called reticular cells; also contains white blood cells Location: in lymphoid organs (lymph nodes, bone marrow, spleen) Fxns: support; in lymph nodes, the fibers trap bacteria. Slide: "Human Reticular Tissue sec. 31-2674 (H6252)" (h. p.) (reticular fibers stain very dark) 3. Adipose
Description: sparse, gel-like matrix; adipocytes (fat cells) have nucleus & cytoplasm pushed to the side by large fat droplet. Location: under skin, around kidneys, eyeballs, and other organs, in bones (yellow marrow) and breasts, and within abdomen. Fxns: energy storage, insulation, supports & protects organs Slide: "Adipose Tissue Fat Stained, w.m." (l. p.) - lipid material inside the adipocytes has been stained red; the cytoplasm has been pushed to the sides of the cells and has been stained purple; you can also see adipose cells that are not stained red (the lipid is gone and you see a white space inside the cell) B. Dense Connective Tissue 1. Dense regular connective tissue (fibers run in same direction) Description: primarily parallel collagen fibers; a few elastic fibers; mostly fibroblasts Location: tendons, most ligaments Fxns: tendons attach muscles to bones or to muscles, ligaments attach bones to bones; withstands tension exerted in one direction. 2. Dense irregular connective tissue (fibers are arranged irregularly) Description: irregularly arranged collagen fibers; some elastic fibers; mostly fibroblasts Location: dermis of skin, submucosa of digestive tract, fibrous joint capsules Fxns: provides structural strength; withstands tension exerted in many directions C. Cartilage - capable of enduring more stress than connective tissues just discussed; unlike other connective tissues, cartilage is avascular and contains no nerves; its strength is due to collagen & elastic fibers; matrix is composed of chondroitin sulfate, hyaluronic acid, and lots of water; chondroblasts produce matrix & when mature (then called chondrocytes), these cells lie in spaces called lacunae. 1. Hyaline cartilage ( gristle ) Description: firm matrix, fibers not detectable, and chondrocytes clearly visible Location: forms most of embryonic skeleton; covers ends of long bones in joint cavities; forms costal cartilages of ribs; nose; trachea; larynx Fxns: support & reinforcement, cushions, resists compressive stress Slide: "Hyaline Cartilage Trachea Human" (l. p.) - id. matrix and chondrocytes 2. Elastic cartilage Description: similar to hyaline, but more elastic fibers Location: external ear, epiglottis ("lid" on top of larynx - prevents food from entering windpipe), eustachian tubes (equalize pressure in middle ear) Fxns: maintains shape while allowing great flexibility 3. Fibrocartilage
Description: matrix less firm than hyaline cartilage; mostly thick collagen fibers Location: intervertebral discs, pubic symphysis (between hip bones), knee joint Fxns: tensile strength with ability to absorb compressive shock D. Osseous (Bone) (2 types of bone tissue: compact & spongy) Description: hard, calcified matrix; collagen fibers; osteocytes lie in lacunae; tissue is well-vascularized (lots of blood vessels); basic unit of organization in compact bone is the osteon; spongy bone will be discussed later under skeletal system. Each osteon consists of: osteocytes (mature bone cells) lacunae (small spaces between lamellae that contain osteocytes) lamellae (rings of hard matrix - look like the growth rings of a tree!) canaliculi (minute canals that project from lacunae and provide numerous routes for nutrients to reach osteocytes and for wastes to be removed from them) a central haversian canal (contains blood vessels and nerves); each osteocyte and its canaliculi look like a spider. Fxns: support; protection; provides levers for muscles to act on; stores calcium, other minerals; yellow marrow stores lipids for energy; red marrow is the site for blood cell formation (hematopoiesis) Slide: "(H155) Bone, c. s., Human, Ground" or Ground Bone Compact Extra Thin (c.s. 71883 (l. p. & h. p.) - this slide is of compact bone (not the spongy bone found in red & yellow bone marrow); id. osteon, osteocytes in lacunae, haversian canal, canaliculi E. Vascular (Blood) Description: erythrocytes (red blood cells), leukocytes (white blood cells), & platelets in a liquid, straw-colored matrix (plasma) Location: liquid within blood vessels Fxns: rbc's - transport of oxygen to cells and carbon dioxide away from them; wbc's phagocytosis, immunity, & allergic reactions; platelets - blood clotting; plasma - transports nutrients, enzymes, hormones, ions, carbon dioxide, etc. Slide: Human Blood Smear Wright (h.p.) - id. erythrocytes (red blood cells - no nucleus, biconcave discs), leucocytes (white blood cells - large, stained purple, nuclei have different shapes); we'll id. thrombocytes (platelets) on oil immersion later on in the semester when we study the cardiovascular system (platelets are cell fragments involved in clotting). III. MUSCLE TISSUE - Muscle tissue is highly specialized to contract. A. Skeletal muscle Description: long, cylindrical, multinucleated cells; obvious striations Location: attached to bones or occasionally to skin Fxns: voluntary movement (it's attached to bones - it makes bones move!), maintenance of posture, heat production (heat is released from all of the chemical reactions taking place during contraction of the muscle) Slide: "Skeletal Muscle - Monkey, l.s. (H9082)" (h. p.) B. Cardiac muscle
Description: branching, striated, generally uninucleated cells that interdigitate at specialized junctions called intercalated discs (these discs allow the muscle to contract as a unit) (under involuntary control) Location: walls of the heart Fxns: contraction propels blood into circulation Slide: "Intercalated discs sec. H1790" (h. p.) - id. intercalated discs - very faint!; you may have to turn the slide to vertical because they placed the tissue on the slide in the wrong direction. C. Smooth muscle Description: spindle-shaped cells with central nuclei; cells arranged closely to form sheets; no striations. (under involuntary control) Location: in the walls of hollow organs (ex. digestive tract, respiratory tract, uterus, blood vessels); in arrector pili muscles of the skin (causes goose bumps) Fxns: in hollow organs, smooth muscle propels substances along internal passageways (ex. food in digestive tract, blood in blood vessels, the fetus in the uterus; eggs in fallopian tubes); heat is given off as a result of many chemical reactions required for muscle contraction and the formation of a goose bump; Slide: "Goblet Cell Epithelium (H215)" (l. p.) - look for smooth muscle tissue in the outer wall of the intestine; the contractions of these muscle cells result in peristalsis (progressive, wavelike contractions that move food through the digestive system). (Hint: you'll know it's smooth muscle - you'll be able to see the intestinal villi on the slide!!) IV. NERVOUS TISSUE Initiates & transmits nerve impulses that coordinate body activities. Nervous tissue is composed of 2 major cell types: neurons and neuroglial cells. Description of neuron: nucleus-containing cell body (soma); cytoplasm is drawn out into extensions (sometimes as long as 3 or more feet!); dendrites are the shorter branched extensions located close to the cell body - dendrites conduct nerve impulses toward the cell body - neurons may have many dendrites; axons are single, long extensions - axons conduct nerve impulses away from the cell body - each neuron has only one axon. Location: Brain, spinal cord, nerves Fxns: neuroglial cells - special supporting cells that protect and insulate neurons, and 2.) neurons - cells specialized to receive stimuli and to conduct nerve impulses to all parts of the body. Slides: 1. "(H390) Motor nerve Cells, Smear, Ox Spinal Cord" (l. p.) - id. neuron soma & dendrites; also id. neuroglial cells ("webby" substance with little purple dots); you won't be able to id. axons on this slide because the axons have broken off; neurons on this slide are called multipolar because they have many dendrites coming off the soma. 2. "Motor Nerve Endings, w.m." (l. p.) - id. axon; you can see the red skeletal muscle cells that the axon is going to cause to contract!); observe the axon branches with bulbs on their ends.