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HUMAN HISTOLOGYIMPORTANT THINGS TO ASK YOURSELF WHEN LOOKING AT &

STUDYING TISSUES1. What does it look like?2. What is the name (be specific)3. Where is it found?4. What is (are) the name(s) of any special cell(s)?5. What is (are) the name(s) of any special structure(s)?6. ALL of the above may not apply to ALL of the tissues studied.

CONNECTIVE TISSUES1. Blood 2. Adipose 3. Areolar connective tissue4. Reticular connective tissue5. DWFCT (regular & irregular)6. Cartilage (hyaline, fibrocartilage. elastic)7. Compact bone

EPITHELIAL TISSUES1. Simple squamous epithelium2. Simple cuboidal epithelium 3. Simple columnar epithelium4. PSCCE5. Transitional epithelium6. Stratified squamous epithelium

a. keratinized (K)b. non-keratinized (NK)

MUSCLE 1. Skeletal (teased & diseased)2. Cardiac3. Smooth

NERVE1. Cerebral cortex 2. Giant multipolar neuron3. Meissner's corpuscle (demo)4. Pacinian corpuscle (demo)5. Node of Ranvier (demo)6. Neuromuscular junction (demo)

MITOSIS1. Prophase2. Metaphase3. Anaphase4. Telophase

SKIN (as an organ)

1. Epidermisa. stratified squamous epidermis - Kb. stratum corneumc. stratum basale {also s.

germinativum}2. Dermis

a. dermal papillaeb. DWFCT (main tissue present)

3. Hair Folliclea. shaftb. bulbc. hair papilla

4. Arrector pili muscle5. Sebaceous gland6. Eccrine gland7. Hypodermis

a. adipose

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HISTOLOGY A tissue consists of a group of cells of similar structure and function, along with the nonliving extracellular substance filling spaces between them. Histologists group all (mature, i.e. not embryonic) human tissues into four major categories: EPITHELIAL, CONNECTIVE, MUSCULAR, and NERVOUS.

You will be expected to accomplish the following: (I) learn to recognize and name the specific types of these four classes of tissues when viewed through a microscope; (ii) name any or all of the structures associated with these tissues; (iii) identify and name the various cells; (iv) name examples of organs or body parts in which these specific tissues may occur; and (v) in some cases describe the function and give the names of specific structures found within the tissue(s). Following is an outline of the tissues that we will examine through the microscope:

I. CONNECTIVE TISSUEA. AreolarB. AdiposeC. ReticularD. Dense White Fibrous

1. Regular2. Irregular

E. Cartilage1. Hyaline Cartilage2. Fibrocartilage3. Elastic Cartilage

F. Vascular (blood)G. Compact Bone

III. MUSCLE TISSUEA. SkeletalB. CardiacC. Smooth

II. EPITHELIAL TISSUEA. Simple Squamous B. Simple CuboidalC. Simple ColumnarD. Pseudostratified ciliated columnar {PSCCE}E. TransitionalF. Stratified Squamous

1. Keratinized2. Non-Keratinized

IV. NERVE TISSUEA. Cerebral CortexB. Spinal Cord (Giant Multipolar Neuron)C. Neuromuscular Junction {NMJ} (demo)D. Sensory Nerve Endings (demo)

1. Meissner=s Corpuscles2. Pacinian Corpuscles

E. Nodes of Ranvier (demo)I. CONNECTIVE TISSUE

Connective tissue is one of the most abundant and varied of all types of tissues in the body. Most connective tissues share the important feature of being composed mainly of MATRIX (extracellular substance) with relatively few cells, whereas epithelial tissues are composed mainly of densely packed cells with little matrix. In most cases, it is the matrix that characterizes connective tissues.

Connective tissue matrix includes fibers embedded in an amorphous GROUND SUBSTANCE. The ground substance varies from a fluid consistency to a semisolid gel (solid in bone). Fibers are composed of the structural proteins COLLAGEN and ELASTIN. Fibers of elastin are called ELASTIC FIBERS (sometimes yellow fibers). Fibers of collagen are referred to as COLLAGEN FIBERS, RETICULAR FIBERS, or OSSEIN FIBERS, depending on the tissue in which they occur.

Many different types of cells are associated with connective tissues: FIBROBLASTS {that produce the fibers}, CHONDROBLASTS {immature cartilage cells}, CHONDROCYTES {mature cartilage cells}, OSTEOCYTES {bone cells}, ADIPOCYTES {fat cells}, ERYTHROCYTES {red blood cells}, and LEUKOCYTES {white blood cells}. Other specialized types of cells may be found in connective tissues, but these are beyond the scope of this class.A. AREOLAR CONNECTIVE TISSUE

Observe on low power a slide labeled AREOLAR TISSUE. This tissue contains long, very thin, thread-like fibers of elastin, a structural protein, called Elastic Fibers. They appear as dark hair-like fibers and provide elasticity to this tissue. Thicker, very pink, non-elastic Collagen Fibers may also be found. Collagen fibers are composed of the most common structural protein in the body ...

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collagen. Both types of fibers extend in all directions, very much as wind-blown hair appears.Numerous cells may be seen composed of obvious dark Nuclei surrounded by pale cytoplasm.

Fibroblasts are the predominant cell present and actually produce the non-living matrix of this tissue. Macrophages {monocytes} are also present. Many different types of blood cell may occur transiently in this tissue. We will make no attempt to distinguish these cells. This tissue is found around organs, between muscles, and in subcutaneous skin {hypodermis}. Areolar connective tissue can often be seen as a very slimy, grayish film adhering to the underlying muscle of chicken (or any other vertebrate) when the skin is removed.

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B. DENSE WHITE FIBROUS CONNECTIVE TISSUE {DWFCT} Dense white fibrous connective tissue {DWFCT} has a shining

white appearance when viewed grossly and is very tough when eaten. (There is also a dense yellow fibrous connective tissue that we will not study).

DWFCT differs from areolar (loose) connective tissue in that it has many more Collagen Fibers and fewer cells. Fibroblasts, although few in number, are the most prevalent cell present. Two major types of this tissue are found in the body. They are described as REGULAR DWFCT and IRREGULAR DWFCT; the difference is determined by the arrangement of the collagen fibers.

Regular DWFCT is found in tendons, ligaments, fasciae, aponeuroses (broad, flat sheet-like tendons), periosteum, and the sclera and cornea of the eye.

You should examine a slide of tendon (the slide MAY be labeled white fibrous tissue). Observe in longitudinal section the thick bundles of pink-staining collagen fibers. The fibroblasts are compressed into thin, wavy purple streaks. (Some slides have cross sections also that you are not responsible for.)

Ligaments connect bone to bone across a moveable joint and are similar to tendons except that they contain many more elastic fibers, thereby exhibiting a greater ability to stretch without tearing.

Fasciae and aponeuroses have the bundles of DWFCT arranged in multiple sheets. In the cornea, each sheet of regular DWFCT is at right angles to the next sheet, as in the layers of plywood.

Irregular DWFCT occurs in the Dermis of the skin and sheaths of nerves. Examine a slide labeled scalp. Look at the dermis and observe the bands of collagen fibers. They appear to be short and extend in all directions, hence the term irregular. This tissue has more elastic fibers than regular DWFCT; therefore, the skin is more elastic than tendons.

C. CARTILAGE Three types of cartilage occur in the human organism: HYALINE, ELASTIC, and FIBROCARTILAGE. They all share similar structures, but there are sufficient differences to make them recognizable. Cartilage differs from other connective tissues in that it is avascular (no blood supply). It consists of cells called Chondroblasts, Chondrocytes and extracellular fibers embedded in an amorphous, gel-like matrix. The cavities within the matrix that contain the chondrocytes are called Lacunae.

1. HYALINE CARTILAGE This is the most abundant type of cartilage. Costal Cartilages attach ribs to the sternum; Articular Cartilages are found at the end of bones in synovial joints. Tracheal Rings in the trachea ("wind pipe") and the Larynx (voice box or "Adam's apple") are other examples of hyaline cartilage. (The epiglottis, part of the larynx, is elastic cartilage.) Examine a slide of trachea (may be labeled AHyaline Cartilage@ on both low and high power. The trachea is a complex organ composed of many tissues. The cartilage appears as a dense purple area with many cavities (Lacunae) filled by cells (Chondrocytes). Surrounding the cartilage is a layer called the Perichondrium. Note the cells are very small, flattened, and arranged more closely together than the mature part of the cartilage. Some of these Chondroblasts are capable of becoming chondrocytes and will do so when the cartilage grows. The perichondrium has a blood supply, although the major portion of all cartilage is avascular.

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2. ELASTIC CARTILAGE

Elastic cartilage is found in the Auricle or pinna, Eustachian Tube and Epiglottis (part of the larynx). The slide you will examine is from the auricle. The cartilage appears (on low power) as a band of tissue running as a wavy strip through the slide. The same structures found in hyaline cartilage may be seen here also: Perichondrium, Lacunae, Chondroblasts. Chondrocytes, and Matrix. Additionally, numerous thin threads of ELASTIC FIBERS are visible. These fibers may appear as very dark, densely packed threads or as very sparse and hard to distinguish fibers depending on the manner in which the slides were stained. They are responsible for giving this cartilage its pliable characteristic.

D. COMPACT BONE Bone exists as two main types of tissue: Compact Bone, that is

found on the surface of bones; and Cancellous Bone, that may be seen as spongy bone on the inner aspects of bones. Mature compact bone is organized into Haversian Systems {Osteons}, each of which exhibits these structures:

a. Haversian Canal: Canal that extends along the length of a bone containing a blood vessel and a nerve.

b. Lacunae: Spaces between the lamellae (layers of matrix) within which the osteocytes occur (mature bone cells).

c. Osteocytes: Mature bone cells trapped in the matrix and occupying the lacunae.

d. Canaliculi: Cytoplasmic processes of osteocytes appearing as tiny hair-like fibers extending from the cell body.

Obtain a slide labeled GROUND BONE and identify the above structures on low power. Note that numerous Haversian systems are visible on the slide. Occasionally, horizontal canals may be seen connecting two Haversian canals. These are called Volkmann's Canals (Not all slides will have a Volkmann=s canal ... be sure to look at your neighbor=s slide).

Bone matrix consists of Ossein Fibers (composed of collagen) embedded in mineralized (calcium salts) ground substance. The protein fibers are not distinguishable on these slides.

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II. EPITHELIAL TISSUESEpithelium covers body surfaces and organs and lines cavities. Each of the following is an

example of epithelial tissue: lining of vagina, outer surface of eardrum, outer surface of eye, covering of uterus, epidermis, lining of aorta, lining of stomach, etc.

All epithelial tissues share certain characteristics: a free border or edge and a basement membrane. They have numerous cells and very little extracellular matrix. An exception to this is the basement membrane which is actually non-living ground substance formed by the underlying connective tissue. Most epithelial tissues are attached to a basement membrane of an underlying connective tissue.

Epithelium is classified and often named according to the number of cell layers and the shape of the cells. If the tissue is one cell thick, it is Simple; if it is more than one cell thick, it is Stratified. Squamous epithelial tissues have flat cells that resemble fried eggs. Cuboidal tissues have cells shaped like a peach, and Columnar tissues are shaped like columns (bananas). Hence, a single layer of flattened cells is called Simple Squamous Epithelium. A single layer of column shaped cells is called Simple Columnar Epithelium, etc.

Within each possible classification of epithelium, the cells may or may not have Cilia on their free border. In human tissues these cilia are generally used to move mucus (and consequently anything trapped in the mucus). Cilia are found, for example, lining the respiratory tract, fallopian tubes, and vas deferens.

A. SIMPLE SQUAMOUS EPITHELIUM

This tissue is found in numerous places: Bowman's capsule of the kidney, lining of alveoli in the lungs, capillary walls, etc. We will use the kidney as an example of this tissue. You should refer to chapter 25 in your textbook and learn the BASIC anatomy of the functional unit of the kidney, namely the NEPHRON. The Glomerulus, Bowman's Capsule, and the Renal Tubule must all be recognized and understood FIRST from diagrams, and only then should you attempt to observe them on the microscope. Each of these nephrons (approx. 1,000,000 in each kidney) are all interwoven with each other. Therefore, when a thin slice of kidney is placed on a microscope slide, one cannot expect to see ANYTHING that resembles the diagram.

Place a prepared slide of KIDNEY on low power. The Glomeruli resemble balls of tissue that are surrounded by a thin white space (Bowman's Space). The glomeruli are numerous and more or less randomly distributed in the Cortex of the kidney. Select a glomerulus and switch to high power. Observe across the space (away from the glomerulus) a thin membrane that is one cell thick. This is a Bowman's Capsule. It totally surrounds the glomerulus but is often difficult to see in its entirety. You may have to look at several glomeruli before you find a good example of a Bowman's capsule. The tissue of which Bowman's Capsule is composed is SIMPLE SQUAMOUS EPITHELIUM.

B. SIMPLE CUBOIDAL EPITHELIUM The Renal Tubule of the kidney is Simple Cuboidal Epithelium

through much of its length. Much of the thyroid gland and the outer covering of the ovary are also Simple Cuboidal Epithelium. Most of the tissue on the kidney slide (exclusive of the glomerulus and Bowman's capsule) is simple cuboidal epithelium. Observe on both low and high power the renal tubules cut in both cross & longitudinal sections.

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C. PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM (= PSCCE)

Look on the trachea slide (may also be labeled pseudostratified ciliated columnar epithelium) at the edge of the tissue for PSCCE. The Cilia are visible on high power. Goblet Cells may also be seen. The tissue appears stratified because it has nuclei at various levels in the different cells. Although the nuclei appear stratified, each column-shaped cell is attached to the basement membrane; therefore, this is a tissue exhibiting false stratification (hence the name).

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D. STRATIFIED SQUAMOUS EPITHELIUM

This tissue consists of multiple layers of cells. The layer next to the underlying connective tissues is cuboidal cells; however, the outermost layer of cells is squamous (flattened). Stratified tissues are always named by the shape of the cell layer at the free border. Two types of this tissue are common in humans:

1. STRATIFIED SQUAMOUS EPITHELIUM NON-KERATINIZED

Found lining the vagina, esophagus, & oral cavity. The epithelial layer is found at the top of the slide. Notice the cells at the surface are flattened and that distinct nuclei are visible. These cells are continuously shed into the oral cavity. The presence of nuclei is a clear indication that keratinization does not occur in this tissue and is useful in distinguishing from the next tissue you will observe (keratinized stratified squamous epithelium). This lining is much thicker in the mature female than the immature or menopausal adult because of the effect of estrogen.

The thicker layer of tissues below the epithelium consists mainly of connective tissues organized into various structures, glands, blood and lymph vessels, nerves (very few), and two unorganized layers of smooth muscle. Near the vaginal orifice the muscle is skeletal rather then smooth.

2. STRATIFIED SQUAMOUS EPITHELIUM - KERATINIZED

The skin is the largest organ in the body and has three layers: epidermis, dermis, and hypodermis. The Epidermis consists entirely of keratinized stratified squamous epithelium over the entire surface of the body with very little difference except on the palms of the hands and soles of the feet where it is much thicker and devoid of hair follicles. Because of this it is often referred to as thick skin or thin skin.

Examine the scalp slide (thin skin) and note the Epidermis, Dermis, and Hypodermis. The epidermis consists of four distinct layers (five on the palms and soles). The bottom-most layer, termed Stratum Basale, consists of a single row of cells next to the dermis. These cells divide (by mitosis), giving rise to the cell layers above. The outer layer of epidermis, the Stratum Corneum, appears somewhat like flaky pie crust near the surface. The cells formed below have all died and been converted into the protein Keratin. They are constantly shed from all of the body surfaces. If excessive shedding occurs from the scalp, it is called dandruff. People allergic to cats, dogs, horses, etc. are actually allergic to the protein in these cells shed by the animal. The stratum corneum is thicker on the palms and soles, especially where a person has a callus or corn.

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III. MUSCLE TISSUEThree types of muscle tissue occur naturally in humans: Skeletal, Cardiac, and Smooth. You must learn to recognize each type and know where it is located in the body.

A. SKELETAL MUSCLE

Place a slide of Teased skeletal muscle on the microscope at 100X. Teased means the muscle fibers have been separated much as in teasing hair. Look for the individual muscle fibers. Note the numerous Nuclei that appear as dark "jelly beans" along the periphery of the fiber. Alternating pale and dark bands called Striations are visible at both low and high power (ADJUSTMENT of the iris diaphragm is critical to maximize the visibility of this characteristic).

This tissue constitutes the ONLY tissue in the body over which you have DIRECT conscious control. For this reason it is sometimes referred to as VOLUNTARY MUSCLE.

Look also a the slide labeled trichinella. This is a worm (Trichinella spiralis) that is a parasite of skeletal muscle tissue. Only animals that eat meat can have this parasite. How does one get the disease called Trichinosis? What is its life cycle?

B. CARDIAC MUSCLE This tissue is found only in the heart with a few fibers extending

into the ascending aorta. Cardiac muscle fibers extend in different directions in the heart. SEARCH for fibers that have been cut LONGITUDINALLY when looking at the slide on low power.

Note the branching of cardiac muscle fibers. This characteristic is distinctly different from other types of muscle. Striations are difficult to see in this tissue. Adjusting the iris diaphragm on high power may help. Intercalated Discs may be seen as partition-like structures at various intervals along the fibers. These discs may appear as a very clear "break" in the fiber or as a dark band transecting it. (Not all slides show these discs well; therefore, one will be on demonstration.)

C. SMOOTH MUSCLE Smooth muscle, like cardiac, is involuntary (that is, not under

conscious nervous control). Its ubiquitous occurrence in the human body includes the following: wall of the uterus, wall of blood vessels, iris of the eye, muscular layer of the stomach & intestinal walls, skin (arrector pili), etc.

Look at a teased smooth muscle slide to observe individual smooth muscle cells. They are very pale and transparent and may be difficult to locate on the slide. You should only use low power and reduce the light with the iris diaphragm until you locate them. Only after viewing and focusing on low power should you switch to high power.

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IV. NERVE TISSUEWe will observe only a few of the many examples of nerve tissue. Two main types of cells will

be visible: Neurons and Neuroglial Cells. The neurons conduct the nerve impulses and in a few cases produce materials for secretion. The neuroglia serve many varied and important functions for the neurons.

A. GIANT MULTIPOLAR NEURONS Giant Multipolar Neurons occur in the gray matter of the spinal

cord. They may be seen as large blue cells with a Nucleus that generally has a small dark-staining Nucleolus prominently visible. The cell body of these cells are referred to as the Soma. This slide is made by smearing the tissue on the slide and is therefore very unorganized. (These are the cells destroyed by the polio virus, resulting in paralysis.)

The long cytoplasmic extensions from these cell bodies are axons and dendrites. (In these slides you cannot tell for sure which are axons & which are dendrites, the noncommital term Neurite is often used). Interspersed among these Giant Multipolar Neurons are small blue dots, which are actually the nuclei of Neuroglial Cells. Neuroglia are the support cells of the nervous system.

V. Skin as an OrganLook at the scalp slide again as an example of the skin as an organ consisting of several types of

tissue. You will need to be able to recognize the 3 layers of the skin as well as the following structures. You will need to use high power on the layers of the epidermis. Everything else on the skin you should observe on low power.

1. Epidermis- The epidermis is keratinized stratified squamous epithelium. It will look like a darker purple layer at the top of the slide. Find these layers of the epidermis:

a. Stratum corneum- This is the outermost layer. It is the keratin layer and looks like flaky pie crust.b. Stratum granulosum- This is a thin layer just under the stratum corneum. This is where keratinization begins, and the cells look “grainy”. The nuclei will be flat.c. Stratum spinosum- This is the thickest layer of the epidermis. The cells are rounded, but the DO NOT look “spiny”. The nuclei will be rounded.d. Stratum basale (stratum germinativum)- This is a single layer of cells at the base of the epidermis.

2. DermisThe dermis is the thickest of the 3 layers of the skin. It consists of irregular dense white fibrous connective tissue. There are also other structures present associated with the skin.a. Dermal papillae- These are wavy “finger-like” projections of the dermis up into the epidermis.b. DWFCT- irregularc. Hair follicle- This is actually an epidermal structure that projects far down into the dermis.d. Hair shaft- This will look like a non-cellular yellowish structure in the hair follicle.e. Arrector pili muscle- This is a strip of smooth muscle. Look for a strip of slightly wavy tissue that runs at an angle in the dermisf. Sebaceous gland- This is an oil gland. The ducts open onto the hair follicle, so it will be close to the base of the hair follicle.g. Eccrine gland- This is a sweat gland. It is a coiled tubular gland. Look at about the level of the sebaceous glands.

3. HypodermisThis is the bottom layer of skin. It is made up of adipose and areolar tissue, but we will only see

adipose tissue.

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SUPERIOR APPENDAGES & PECTORAL GIRDLESCAPULA transverse scapular spine

RADIUS radial tuberosity

HANDnavicular (scaphoid) lunate triangular (triquetrum)pisiform greater multangular (trapezium)lesser multangular (trapezoid)capitate hamate proximal phalanx MIDDLE phalanx distal phalanx (pl.= phalanges) metacarpals (1-5)

ULNAolecranon process

HUMERUSmedial epicondyle

CLAVICLE

INFERIOR APPENDAGES AND PELVIC GIRDLEOS COXA body of ilium ischium pubis

FEMUR lateral condyle

FIBULAlateral malleolus

TIBIAmedial malleolus

FOOTdistal phalanx MIDDLE phalanx proximal phalanxmetatarsals (1-5)taluscalcaneusnavicular first cuneiformsecond cuneiform third cuneiformcuboid

PATELLA

VERTEBRAL COLUMN, STERNUM, RIBSVERTEBRA SACRUM1. Centrum Coccyx 2. Vertebral foramen (spinal canal) RIBS

STERNUM

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BONES OF THE CRANIUM AND FACEMANDIBLEmental foramen

MAXILLA

anterior nasal spine

FRONTAL supraciliary ridge (arch)

TEMPORAL styloid process (often broken)

OCCIPITALexternal occipital protuberance

SPHENOIDsella turcica {Turk's saddle}

ETHMOIDcrista galli cribriform plate

ZYGOMATICtemporal process

BONES W/O STRUCTURESPALATINEPARIETALNASAL VOMER LACRIMAL HYOID

AUDITORY OSSICLESMALLEUSINCUSSTAPES

SUTURES lambdoidalsquamosalcoronal sagittal

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STRUCTURES OF THE SHEEP BRAIN

The brain is divided into three main regions. The FOREBRAIN includes the CEREBRUM, THALAMUS, and HYPOTHALAMUS. The MIDBRAIN consists of the TECTUM and TEGMENTUM. The HINDBRAIN is made up of the CEREBELLUM, PONS VAROLII, and MEDULLA OBLONGATA.

* 1. Sulcus (pl. = sulci)* 2. Gyrus (pl. = gyri)* 3. Longitudinal & Transverse fissures* 4. Cerebrum (2 hemispheres; 4 lobes

each)** 5. Corpus Callosum** 6. Lateral Ventricle** 7. Fornix* 8. CN I Olfactory (nerve)* 9. Olfactory Tract(nerve vs tract??)* 10. CN II Optic* 11. Optic Chiasma* 12. Optic Tract** 13. Thalamus* 14. Hypothalamus (the brain tissue

surrounding the 3rd ventricle)* 15. Mammillary Body (part of the

hypothalamus***16. Midbrain

* 17. Pineal Body - lies between the superior colliculi

** 18. 3rd ventricle** 19. 4th ventricle***20. Cerebellum

Arbor Vitae***21. Pons ***22. Medulla Oblongata

These structures are not part of the brain, but are associated with it:

***23. Spinal Cord** Spinal Canal** 24. Meninges

Dura Mater (demo)Arachnoid MaterPia Mater

* Locate these structures on the whole brain only.** Locate these structures on the sagittal sectioned brain only.*** Locate these structures on the whole brain and the sagittal section.

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STRUCTURES OF THE EARPINNA {AURICLE} HelixTRAGUSTYMPANIC MEMBRANEEXTERNAL EAR

External Auditory MeatusExternal Auditory Canal (cerumen)

MIDDLE EARAUDITORY OSSICLES = Malleus, Incus, & Stapes EUSTACHIAN TUBEINNER EARPETROUS PORTION OF TEMPORAL BONE INTERNAL AUDITORY MEATUSSEMICIRCULAR CANALS (DYNAMIC BALANCE)VESTIBULE (STATIC BALANCE)COCHLEA (Round window & Oval window)

Structures of the Eye

1. SHEEP EYE DISSECTION: the following structures must be found on the sheep eye:Pupil Blind spot Anterior cavityIris Lens Anterior chamberSclera CN II Optic nerve Posterior chamberChoroid layer Ciliary body (muscle) Posterior cavityTapetum lucidum Retina Vitreous humorBulbar conjunctiva Postorbital adipose Cornea

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