Tissue

· Tissues are the group of call having similar structure which together to perform a specific function.

· Four general categories of animal tissue

§ Epithelial Tissue

§ Muscle Tissue

§ Nerve Tissue

§ Connective Tissue

Epithelial tissue

· Found on a body surface either internal or external

· Tightly packed cells

· Free border or free surface

· Rest on a basement membrane

· Nonvascular

· Function –

§ First line Protection from environment.

§ Coverage.

§ Secretion and excretion.

§ Absorption.

§ Filtration.

Classifying epithelial tissue

· Simple squamous epithelium –

§ Appearance in thin scales,

§ Nuclei of squamous cell tend to appear flat, horizontal, and elliptical, mirroring the form of the cell.

§ Prevent rapid passage of chemical compound is necessary such as the lining of capillaries and small air sacs of lungs.

§ Composing the mesothelium which secretes serous fluid to lubricate internal body cavity.

· Simple cuboidal epithelium –

§ Cell appears round.

§ Nucleus located center of the cell.

§ Involved in secretion and absorption of molecules requiring active transport.

§ Observed in the lining of kidney tubules and ducts of glands.

· Simple columnar epithelium –

§ Nucleus tends to elongated and located in the basal end of the call.

§ Composed of simple columnar epithelium cells with cilia on their apical surfaces.

§ Involved in secretion and absorption of molecules requiring active transport.

§ Forms a majority of digestive tract and some port of female reproductive organs.

§ Found in lining of fallopian tube and part of respiratory system, where cilia helps remove particulate matter.

· Stratified squamous epithelium –

§ Consist of squamous epithelial cell arrange in layers upon a basal membrane.

§ Apical cells appears squamous, while basal layer contains either columnar or cuboidal cell.

§ Most common type of stratified epithelium in human body.

§ Found in nearly every organs which come in to close contact with outside environments such as respiratory, digestion, excretory and reproductive systems.

§ Top layer may be covered with dead cell containing keratin e.q. skin.

§ Provides protection against mechanical stress, chemical abrasions, and even radiation.

§ Protect the body from desiccation and water loss.

· Stratified cuboidal epithelium –

§ Composed of multiple layers of cube shaped cells

§ Superficial layer is made up of cuboidal cells, other layers can be other type cells.

§ Found in certain glands and ducts such as conjunctiva, pharynx, anus and male urethra.

§ Rare in human body.

§ Makes multiple membrane junction between adjacent cells.

§ Creates an impermeable barrier between two distinct surfaces in the body.

§ Barriers act like a filter, forcing nutrients and water to pass through the cell.

· Stratified columnar epithelium –

§ Composed of column shaped cell arranged in multiple layers.

§ Found in certain glands and ducts such as conjunctiva, pharynx, anus and male urethra.

§ Rare in human body.

§ The main function is protections, it protects the underlying tissue and internal organs against several physical and microbial damages.

§ Protect the conjunctiva and other eye structure.

· Pseudostartified columnar epithelium –

§ Appears to be stratified but consist of a single layer of irregularly shaped and different size epithelium.

§ All cell are in contact with basal lamina, although some do not reach the apical surface.

§ Found in respiratory tract, where some of cell have cilia.

§ Nuclei of neighboring cell appear at different level then clustered in basal end.

§ The arrangement give the appearance of stratification.

§ Heterogeneous epithelia they include additional type of cell interspersed among the epithelial cells.

Muscle tissue

· Muscle tissue is specialized for contraction.

· Calls are elongated, and are also known as muscle fibers.

· Contain the contractile proteins actin and myosin, which interact to shorten and elongate the cells.

Types of muscle tissue:

1. Skeletal Muscle

· Attached to bones, and contraction of these muscles generates body movements.

· The skeletal muscle fibers are long and cylindrical, with multiple peripherally located nuclei.

2. Cardiac Muscle

· Present in the heart.

· Cells are striated, but the striations are much less obvious than in skeletal muscle tissue.

· The cells are shorter than skeletal muscle fibers, have a single nucleus and are often branched.

· Individual cells are connected via gap junctions and desmosomes.

3. Smooth muscle

· Found in the walls of hollow organs, such as the G.I. tract, blood vessels, and the urinary bladder.

· Contractions of these muscles propel fluid or materials through the organs (food through the GI tract, blood through blood vessels, urine pushed out of bladder).

· Smooth muscle cells are not striated; they have a single nucleus, and have tapered ends.

· In blood vessels there is a layer of smooth muscle deep to the epithelial layer.

· It is thicker on the artery than on the vein, but can be seen in both.

Nervous tissue

· Specialized for communication and composes the brain, spinal cord, and peripheral nerves.

· Consists of two major cell types: neurons and glial cells.

· Neurons communicate with each other via electrical and chemical signals.

· They have nucleated cell bodies and two types of elongated cellular processes: dendrites – which receive signals, and axons – which send signals.

· Glial cells are the support cells of nervous tissue.

· Maintaining proper ion concentrations in the fluid surrounding neurons,

· Generating myelin (an insulating material that surrounds some axons),

· Cleaning up debris.

· The large neurons with their elongated cellular processes and the smaller, more numerous glial cells.

Connective Tissue

· Tissue that connects, separates and support all type of tissue in body.

· Connective tissues vary widely in their form and function, but they are all characterized by the presence of extracellular matrix.

· The extracellular matrix is nonliving material composed of protein fibers and ground substance.

· The protein fibers are composed of collagen (which gives strength) or elastin (which gives flexibility).

· The number and type of fibers differs between the various types of connective tissue.

· The ground substance fills the spaces between the cells and the fibers.

· It contains interstitial fluid (tissue fluid) and large polysaccharide molecules.

· The consistency of the ground substance can vary from liquid to gel‐like to a solid.

Type of connective Tissue

1. Dense connective tissue

· Fewer cells then loose

· ECM is densely packed with collagen fibers

· Arrangement of fibers there are two sub type

§ Dance regular connective tissue – collagen aligned parallel to each other, provide unidirectional resistance to stress.

§ Dance irregular connective tissue – collagen fiber randomly interwoven, forming three dimensional network resistance to distension in all direction. Usually located in capsule and wall of organs, dermis and glands.

2. Loose connective tissue

· Also called areolar connective tissue

· Flexible

· Not very resistance to mechanical stress

· Almost equal amount of cells, fibers and ground substance

· Binding other tissue type together for joining tissue with organs

· Most widely distributed type of connective tissue found in lining of body surface

3. Specialized connective tissue

1. Reticular connective tissue

· Produced by modified fibroblasts called reticular cells.

· Similar to dance connective tissue, it produced reticular fiber arranged in an interlaced network.

· Reticular fibers are thinner, compose a more delicate mesh, with reticular cell remaining bonded to the fibers.

· Supports the stroma of body organs especially lymphoid.

· Filter lymph and provide passage and attachment of WBC.

2. Cartilage

· Avascular Connective Tissue

· Connect bones at joint

· Comprises wall of upper respiratory airways and external ear.

· Surrounded by pericardium

· Pericardium is reach in blood vessels and supply to cartilage.

· Chief call called chondrocytes.

· EMC makes cartilage flexible in various degree but resistance to mechanical stress.

· Three type-

§ Hyaline Cartilage – most represented type, rich in collagen ii molecule, found on articular surface of joint, wall of upper respiratory airways and medial ends of ribs.

§ Elastic Cartilage – most elastic fibers, found in the wall of external ear, cuneiform cartilage in the larynx and epiglottis.

§ Fibrocartilage – mainly collagen I molecules, comprises articular discs, such as intervertebral disc, pubic symphysis and knee menisci.

3. Bone

· Comprises the body skeleton.

· Produced by osteoblasts, osteocytes and osteoclasts.

· Osteoblasts produce cell matrix

· Dormant osteoblast called osteocytes.

· Osteoclasts absorb bone matrix.

· Synchronized of these call is necessary for recovery of fracture bone and general wellbeing.

· Allow to serve as storage site for calcium and phosphate.

· Composed of cells within an extracellular matrix of fibers and ground substances.

· Extracellular bone matrix is mineralized and arranged in circular layers known as lamellae.

· Lamellae circumvent around a central canal which provide passage of neurovasculature.

4. Blood

· Specialized connective tissue within circulatory system.

· It has cellular and extracellular components.

· Extracellular matrix of blood known as blood plasma.

· Blood cell carried by plasma are erythrocytes (RBC), leukocytes (WBC), and thrombocytes (Platelets).

· Produced in bone marrow in the process of haematopoiesis.

5. Adipose Tissue

· Energy storing connective tissue.

· Consist of Adipocytes, cell filled with lipids.

· Small amount of ECF made up of few collagen fiber for keep cell together.

· Two type of adipose tissue –

§ Brown Adipose Tissue – each cell contain multiple fat drops, surrounding centrally positioned nucleus. Usually found in baby for energy storage and serve as thermogenesis.

§ White Adipose Tissue – predominant found in adults, store energy, cushions and protect organs and secreting Hormones. Distributed in visceral and parietal fats

· Visceral fats surround and support body organs, such as eyeball and kidney.

· Parietal fats aggregations embedded in the connective tissue of the skin, topically in the abdominal, back and thigh.

6. Embryonic connective tissue

· Found in early embryos and umbilical card.

· Chief call are mesenchymal cells.

· Divided into mesenchyme embryos) and mucoid connective tissue (Umbilical card).

· Mesenchyme originates from mesoderm, one of the three layers of embryos.

· Matures into other type of connective tissue, muscles, vessels, mesothelium and urogenital system.

The Tissue Level of organization PDF