Lecture on Tissues

8/9/2019 Lecture on Tissues

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GENERAL ZOOLOGY

TISSUES

Cells are the smallest units of life. In complex organisms, cells group together with one another

based on similar structure and function to form tissues.

Tissue – group of cells with similar structure and functions, as well as similar extracellular

substances located between the cells.

Histology – microscopic study of tissue structure

Classifications of Tissues:

The human body is composed of four basic types of tissues; epithelium, connective,

muscular, and nervous tissues.

1. pithelium! lines and covers surfaces

". Connective tissue! protect, support, and bind together #. $uscular tissue! produces movement

%. &ascular tissue ! transporter %. 'ervous tissue! receive stimuli and conduct impulses

I E!it"elial Tissue

Characteristics of pithelial Tissues

1. pithelium is arranged so there is one free surface (apical surface) and one attached

surface (basal surface).

". Cells in epithelium fit closely together side by side and sometimes atop each other toform sheets of cells. These sheets are held together by speciali*ed +unctions.

#. pithelium typically lacs its own blood supply.%. pithelium cells can regenerate if proper nourished.-. orms parts of all the sense organs.

unctions of pithelial Tissues1. /rotecting underlying structures

• xamples include the sin and the epithelium of the oral cavity, which protect

the underlying structures from abrasion.

". 0cting as barriers

• pithelium prevents the movement of many substances through the epithelial

layer. or example. The sin acts as a barrier to water and prevents water loss

from the body. The sin is also a barrier that prevents the entry of many toxicmolecules and microorganisms into the body.

#. /reventing the passage of substances

• pithelium allows the movement of many substances through the epithelial

layer. or example, oxygen and carbon dioxide are exchanged between the airand blood by diffusion through the epithelium in the lungs.

%. ecreting substances

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• xamples include the sweat glands, mucous glands, and the en*yme!secreting

portion of the pancreas.

-. 0bsorbing substances

• The cell membranes of certain epithelial tissues contain carrier molecules that

regulate the absorption of materials. or example, the epithelial cells of the

intestine absorb digested food molecules, vitamins and ions.

Types of pithelial Tissues

1. 0ccording 0rrangement

a. Si#!le! Cells are found in a single layer attached to the basement membrane b. St$atifie%! Cells are found in " or more layers staced atop each other

c. &seu%ost$atifie%! a single layer of cells that appears to be multiple layers due to

variance in height and location of the nuclei in the cells.d. T$ansitional! cells are rounded and can slide across one another to allow

stretching.

". 0ccording to hape

a. S'ua#ous – flat, thin, scale!lie cells. b. Cu(oi%al – cells that have basic cube shape. Typically the cell2s height and width

are about e3ual.

c. Colu#na$ – tall, rectangular or column!shaped cells. Typically taller than theyare wide.

#. pecial eatures of pithelial Tissues

a. Cilia ! hair!lie appendages attached to the apical surface of cells that act assensory structures or to produce movement.

b. Go(let cells! speciali*ed cells that produce mucus to lubricate and protect the

surface of an organ

c. )illi ! finger!lie pro+ections that arise from the epithelial layer in some organs.

They help to increase surface area allowing for faster and more efficientadsorption.

d. *ic$o+illi! smaller pro+ections that arise from the cell4s surface that also increasesurface area. 5ue to the bushy appearance that they sometimes produce, they are

sometimes referred to as the brush border of an organ.

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/CIIC T6/

, Si#!le S'ua#ous E!it"eliu#

• ingle layer of flat, often hexagonal cells. The nuclei appear as bumps when

viewed as cross section because the cells are so flat

• 7ocated on lining of blood vessels. 7ymphatic vessels, heart, alveoli and

serous membranes.• It serves as protection against friction, filtration, diffusion, secretion and

absorption.

- Si#!le Cu(oi%al E!it"eliu#

• ingle layer of cube!shaped cells; some cells have microvilli or cilia.

• 7ocated on portions of idney tubules (proximal and distal nephron,

ascending loop of 8enle, and collecting duct), some glands and their ducts,

choroid plexus of the brain, lining of terminal bronchioles of the lungs, and

the surface of ovaries.

• unctions in active transport and facilitated diffusion result in secretion and

absorption by cells of the idney tubules, secretion by cells and the choroid

plexus, movement of particles embedded in mucus out of the terminal

bronchioles by ciliated cells.

. Si#!le Colu#na$ E!it"eliu#

• ingle layer of tall, narrow cells. ome cells have cilia or microvilli.

• 7ocated at the lining of stomach, intestines, some glands, some ducts, portions

of bronchioles of the lungs, auditory tubes, uterus, and uterine tubes.

• ecretion by cells of the stomach, intestines, and glands, absorption by cells of

the intestine, movement of cilia clears mucus.

/ &seu%ost$atifie% Colu#na$ E!it"eliu#

• ingle layer of cells; some cells are tall and thin and reach the free surface,

and others do not. The nuclei of these cells are at different levels and appearstratified. The cells are almost always ciliated and are associated with goblet

cells that separate mucus onto the free surface.

• 7ocated at the lining of nasal cavity, nasal sinuses, auditory tubes, parts of the

pharynx, trachea, and bronchi of the lungs.

• ynthesis and secretion of mucus onto the free surface and movement of

mucus that contains foreign particles over the free surface and from passages.

0 St$atifie% S'ua#ous

• $ultiple layers of cells that are cuboidal in the basal layer and progressively

flattened toward the surface.

• 7ocated in the sin, mouthm throat, larynx, esophagus, anus, vagina, inferior

urethra and cornea.

• /rotection against abrasion, barrier against infection, and prevents loss of

water from the body.

1 T$ansitional E!it"eliu#

• tratified cells that appear cuboidal when the organ or tube is not stretched

and s3uamous when the organ or tube is stretched by fluid.

• 7ocated in the lining of urinary bladder, ureters and superior urethra.

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• 0ccommodates fluctuations in the volume of fluid in an organ or tube;

protection against the caustic effects of urine.

II Connecti+e Tissue

Characteristics of Connective Tissues

1. Connective tissues tend to be very vascular (have a rich blood supply). omeexceptions, such as tendons, ligaments, and cartilages, are less vasculari*ed, but

overall, connective tissues possess a great blood supply than the epithelial tissue

previously discussed.". $ost abundant and widely distributed tissue type found in the human body.

unctions of Connective Tissues1. Connecting tissues to one another

• Tendons are strong cables, or bands, of connective tissue that attach muscles

to bone, and ligaments are connective tissue bands that hold bone together.

". upporting and moving

• 9ones of the seletal system provide rigid support for the body, and semirigid

cartilage supports structures such as the nose, ears, and surfaces of +oints.#. toring

• 0dipose tissue stores high!energy molecules and bones store minerals such as

calcium and phosphate.

%. Cushioning and insulating

• 0dipose tissue cushions and protects tissues it surrounds and provides an

insulating layer beneath the sin that help conserve heat.

Types of Connective Tissues

1. 7oose Connective Tissuea. 0reolar

• 0reolar connective tissue isthe most widespread

connective tissue of the body.

• It is used to attach the sin to

the underlying tissue.

• It fills the spaces between

various organs and thus holds

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them in place as well as cushions and protects them. It also surrounds

and supports the blood vessels.

• The fibres of areolar connective tissue are arranged in no particular

pattern but run in all directions and form a loose networ in the

intercellular material.

b. 0dipose• Characteri*ed by a large

internal fat droplet, which

distends the cell so that the

cytoplasm is reduced to athin layer and the nucleus

is displaced to the edge of

the cell.

• 0dipose tissue, in addition

to serving as a storage site

for fats (lipids), also pads

and protects certain organsand regions of the body. 0s well, it forms an insulating layer under the

sin which helps regulate body temperature.

• /redominantly located beneath the sin, around organs such as the heart

and idneys, and in the breasts.c. :eticular

• resembles areolar connective

tissue, but the only fibers in itsmatrix are reticular fibers,

which form a delicate networ

along which fibroblasts called

reticular cells lie scattered.0lthough reticular fibers are

widely distributed in the body,

reticular tissue is limited tocertain sites.

• found around the liver, the idney, the spleen, and lymph nodes, as

well as in bone marrow.

• support the lymphoid

organs (lymph

node stromal cells, red

bone marrow,and spleen)

". 5ense Connective Tissue

a. Collagenous

• $atrix consists almost

entirely of collagen

fibers produced by

fibroblasts; the fibers

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http://en.wikipedia.org/wiki/Lymphatic_system#Lymphoid_tissue


http://en.wikipedia.org/wiki/Lymph_node


http://en.wikipedia.org/wiki/Lymph_node_stromal_cell


http://en.wikipedia.org/wiki/Red_bone_marrow



http://en.wikipedia.org/wiki/Spleen













can all be oriented in the same direction or in many different

directions.

• 7ocated mostly in tendons, ligaments, dermis of the sin and organ

capsules.

• 0ble to withstand great pulling forces and resists stretch in the

direction of fiber orientation. b. lastic

• $atrix is

composed of

collagen andelastic fibers

oriented either

in the samedirection or in

many different

directions.

• 7ocated mostlyin the walls of elastic arteries, ligaemts between vertebrae and along the dorsal aspect

of the nec, and in vocal cords.

• 0ble to stretch and recoil lie a rubber band with strength in the

direction of fiber orientation.

#. peciali*ed Connective Tissue

a. Cartilage

• :ubbery tissue made by cells called chondroblasts.

• 5oes not have any blood vessels within it so healing is not easy if it is

damaged and may not occur at all if the damage is extensive enough.

Types of Cartilage Tissuei. 8yaline Cartilage

• $ost abundant type of cartilage

• olid matrix with small and evenly dispersed collagen

fibers throughout the ground substance maing the matrix

appear transparent; chondrocytes are found within lacunae.

• ound in costal cartilage of the ribs, cartilage rings of the

respiratory tract, in the nasal cartilages, growth plates of

bones.

• orms smooth, resilient surfaces that can withstand

repeated compression.ii. ibrocartilage

• imilar to hyaline cartilage however collagen fibers are

more numerous than in hyaline and elastic cartilage andthey are arranged in thic bundles.

• It is found in diss between vertebrae, and in some +oints

such as the nee and temporomandibular +oints.

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• Capable of withstanding considerable pressure and is able

to resist pulling or tearing forces.

iii. lastic Cartilage

• tructure is similar to hyaline cartilage, but matrix also

contains abundant elastic fibers.

• /rovides rigidity, but with more flexibility than hyalinecartilage because elastic fibers return to their original shapeafter being stretched.

• They are found in the external ears, epiglottis and auditory

tubes.

b. 9one Tissue

• 8ard connective tissue that consists of living cells and a minerali*ed

matrix.

• 9one cells, or osteocytes are located within spaces in the matrix called

lacunae.Types of 9one Tissue

i. Compact bone

• closely paced osteons or haversian systems.

ii. pongy bone

• basically bone tissue with many spacesstruts and is covered by

compact bone.

• this is where you find red bone marrow.

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• spongy bone is found on the ends of long bones and within flat

and in some irregular bones.

III *uscula$ Tissue

everal specific terms are used exclusively for muscle tissue. or example, muscle cells are

called fibres; their cytoplasm is termed sarcoplasm; and their cell membrane is referred toas sarcolemma.

Characteristics of $uscular Tissue

1. 7ong, elongated, slender cells thus are more appropriately called muscle fibers. Thedelicate membrane covering of a muscle fiber or cell is called sarcolemma.

unctions of $uscular Tissue1. or movement and locomotion

". <ives shape to the body

Types of $uscular Tissue

1. triated or eletal

". 'onstriated or mooth $uscle#. Cardiac $uscle

9asis of Comparison eletal $uscle mooth $uscle Cardiac

7ocation 0ttached to the

seleton

=all of the stomach

and intestines

=alls of the heart

tructure 0 ppear striated Tapered at each end, Cylindrical and

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(banded). Cells are

large, long, and

cylindrical, with many

nuclei located at the

periphery

are not striated, and

have a single nucleus.

striated and have

single, centrally

located nucleus. They

are branched and

connected to one

another by

intercalated diss.

unction $ovement of the

body; under voluntary

control

:egulates the si*e of

organs, forces fluid

through tubes,

controls the amount of

light entering the eye

under involuntary

control

/umps the blood and

is under involuntary

control.

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I) )ascula$ Tissue

Characteristics

1. 0 fluid or li3uid tissue

". It consists of a li3uid part called plasma and formed elements called cells (erythrocytes,

leucocytes and thrombocytes or platelets).

unctions of &ascular Tissue1. Transports and distributes food materials, gases (oxygen and carbon dioxide), hormonesand other waste products.

ormed lements or Cells in &ascular Tissue1. rythrocytes or :ed 9lood Cells (:9C)

a. disc!shaped cell with a thic rim and a thin sunen centre.

b. >riginated from red bone marrow of long bones". Thrombocytes or 9lood /latelets

a. Tiny bodies about ? the diameter of the :9C, colorless and non!nucleated.

b. :elated to blood clotting.

#. 7eucocytes or =hite 9lood Cells (=9C)a. The soldiers of the body – fight infections

b. >rigin – lymph glands and some from the bone marrow

Types of 7eucocytesi. <ranulocytes – with granules in the cytoplasm; nucleus varies in shape.

1. 'eutrophil ! play roles in the destruction of bacteria and the release

of chemicals that ill or inhibit the growth of bacteria.

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". osinophil ! function in the destruction of allergens and

inflammatory chemicals, and release en*ymes that disable

parasites.#. 9asophils ! secrete histamine which increases tissue blood flow via

dilating the blood vessels, and also secrete heparin which is an

anticoagulant that promotes mobility of other =9Cs by preventingclotting.

ii. 0granulocytes – without granules in the cytoplasm.

1. 7ymphocyte – smaller spherical cell with the nucleus almostoccupying the entire cell; cytoplasm is very small in amount.

unction in destroying cancer cells, cells infected by viruses, and

foreign invading cells. In addition, they present antigens to activate

other cells of the immune system. They also coordinate the actionsof other immune cells, secrete antibodies and serve in immune

memory.

". $onocyte ! They are the largest of the formed elements. Their

cytoplasm tends to be abundant and relatively clear. They functionin differentiating into macrophages, which are large phagocytic

cells, and digest pathogens, dead neutrophils, and the debris ofdead cells. 7ie lymphocytes, they also present antigens to activate

other immune cells.

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) Ne$+ous Tissue

Components of nervous tissue are speciali*ed for the conduction of electrical impulses,

which allow communication among other tissue types.

$a+or structural and functional @unit@ of nervous tissue is the nerve cell called neuron.

unction of 'ervous Tissue

• To receive and transmit impulses

/arts of 'euron

1. Cell body or cytosomal body

o The largest part of a neuron and contains the neuron4s nucleus,

associated cytoplasm, and other cell structures.

o The cell body produces proteins needed for the construction of other parts of

the neuron.

". 5endrite

o The shorter, much branched (tree!lie) protoplasmic process that transmits

impulses towards the cell body.

#. 0xon

o The short or long unbranched protoplasmic process that transmits impulsesaway from the cell body.

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http://biology.about.com/od/cellanatomy/p/nucleus.htm

http://biology.about.com/od/biologydictionary/g/cytoplasm.htm

http://biology.about.com/od/cellanatomy/a/eukaryprokarycells.htm


http://biology.about.com/od/cellanatomy/p/nucleus.htm

http://biology.about.com/od/biologydictionary/g/cytoplasm.htm




Types of 'eurons

1. 0ccording to tructure

a. Anipolar – with one cell body and one axon

b. 9ipolar – with one cell body, one axon and one dendrite.

c. $ultipolar – with one cell body, one axon and several dendrites.

". 0ccording to unctiona. ensory – pic!up impulses from sensory

receptors (sin or sense organs) and transmit

them to nerve centers (brain and spinal cord). b. $otor – carry impulses from the nerve

centers to effectors lie muscles or glands.

c. 0ssociation neurons (Interneuron) – from

various connections between other neurons(between sensory and motor neurons)

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Lecture on Tissues

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