Tissue - Level of organization notes PPT/PDF



·         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


The Tissue Level of organization PPT

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