Animal Tissues

ANIMAL TISSUES FOUR basic types of tissues CON-MEN

Read pg 807, Animal structure and function: An introduction

Learning objectives At the end of this topic, you should be able to: • •

List the FOUR main types of animal tissues. From pictographs or diagrams, correctly

(1) Identify the following animal tissues and describe their location in our body system, (2) Explain how their structure relates to function and give examples of each. A. B. C. D.

Epithelial tissue (cuboidal, columnar, squamous) Connective tissue (adipose, cartilage, bone) Muscle (skeletal, cardiac, visceral/ smooth) Nervous

How do these relate to one another? Body (organ) systems

Cells

Tissue s

Organs

Figure 1 illustrates how tissues fit into the hierarchy of body components. ORGANIZATION OF THE BODY Cells > into tissues, tissues > into organs. Several organs > form organ systems.

Introduction: Animal tissues

• Only four types of tissues, dispersed throughout the body: – – – –

epithelial tissue, connective tissue, muscle tissue, and nerve tissue.

• A type of tissue is not unique for a particular organ and all types of tissue are present in most organs, just as certain types of cells are found in many organs. • For example, nerve cells and circulating blood cells are present in virtually all organs

(1) Epithelial tissue Epithelial tissues cover the body and line its cavities

Epithelial tissue SIMPLE EPITHELIUM Simple squamous epithelium Simple cuboidal epithelium Simple columnar epithelium STRATIFIED EPITHELIUM Stratified squamous (keratinized) epithelium Stratified squamous (nonkeratinized) epithelium PSEUDOSTRATIFIED EPITHELIUM Pseudostratified ciliated columnar epithelium SPECIALIZED EPITHELIUM Exocrine glands Endocrine glands

Criteria for classifying epithelium: (1) Number of layers, (2) Shape & (3)

Free surface

• Number of layers

– (1) Simple epithelium: ONLY one layer of cells – (2) Stratified epithelium: MORE than one cell layer

• Shape – (1) Squamous epithelium: • Cell appear flattened or scale-like

– (2) Cuboidal epithelium: • Cell height is the same as cell width

– (3) Columnar epithelium: • Cell height is greater than cell width

• Free surface – (1) Ciliated epithelium (Cilia are present at the cell surface) – (2) Non-keratinized epithelium/ moist – (3) Keratinized epithelium/ dry Two or more of these criteria are often used to classify each type of epithelium E.g. Epidermis of skin > Keratinized stratified squamous epithelium Epithelium of esophagus > Moist type of stratified squamous epithelium

Simple squamous epithelium Nucleus

Description: Single layer of flat cells, centrally located nucleus Location: Lining the air sacs of the lungs, capillary walls and blood vessels (diffusion of nutrients and gasses)

Like floor tiles!! Epithelium (n): Singular Epithelia (n): Plural Epithelial (adj): e.g. epithelial cells, epithelial tissue, epithelial membrane

Function: cells very thin and leaky, permits the rapid movement molecules Lining of blood andof lymph vessels >> endothelium~ structurally similar (e.g. rapid diffusion of to squamous epithelial cells gasses), exchange

Simple cuboidal epithelium Like dice!!

Description: Single layer of cube –shaped cells, centrally located nucleus Function- cells rich in specific transport channels, functions in secretion and absorption. Location-Lining of some glands (e.g., thyroid

Simple columnar epithelium Description: Single layer, column-like cells with nuclei near base of the cells, contains goblet cells and cells with microvilli in some locations Function Thicker cell layer, provides protection and functions in secretion and absorption. Location surface lining of stomach, intestines and parts of respiratory tract

Simple columnar epithelium Simple columnar epithelium (1) airways of the respiratory tract and (2) in the gastrointestinal (stomach and intestine) tract. Interspersed among the columnar epithelial cells are goblet cells, specialized to secrete mucus. Respiratory airways contain cilia on their apical surface (the surface facing lumen/cavity). Small intestine, the apical surface of the columnar epithelial cells form fingerlike projections called microvilli,  increase the surface area for the

• Goblet cells are glandular simple columnar epithelial cells whose sole function is to secrete mucus • They are found scattered among the epithelial lining of many organs, especially the intestinal and respiratory tracts.

Note the brush border made up of microvilli. Goblet type cells release secretions of mucus.

Stratified squamous epithelium Description: – Several cell layers thick, cuboidal to columnar shape in deep layers, squamous cells form the apical layer and several layers deep to it, cells from the basal layer replace surface cells as they are losr

Function: – Tough layer of cells; provides protection Location: E.g. Epidermis (skin), lining of the oesophagus

Stratified squamous epithelium • Stratified squamous epithelia regenerate rapidly – by cell division near the basement membrane.

• The new cells are pushed to the free surface as replacements for cells that are continually sloughed off. • Is commonly found on surfaces subject to abrasion, such as the outer skin and linings of the esophagus, anus and vagina. • The organization of this type of tissue ensures that abrasion affects the oldest

Stratified squamous epithelium (keratinized vs nonkeratinized) • Stratified squamous keratinized epithelium (skin) – Upper layer consists of dead squamous cells Dried, SKIN Vs LIPS – Filled with a water-resistant protein called keratin chapped easily Water resistant property of keratin

Pseudostratified ciliated columnar epithelium Description: consisting of closely packed cells which appear to be arranged in layers BUT all of which are in fact attached to the basement membrane

• Function

– Secretes mucus, dense with cilia that aid in movement of mucus, provide protection

• Location – Lining the respiratory tract

A single layer of cells, varying in

Pseudostratified ciliated columnar epithelium

Cilia Vs Microvilli • Cilia: – Cellular projection from the surface of the cell, 9+2 arrangement (as in flagellum) – Move fluid, mucus and dissolved materials over some exposed cell surfaces

• Microvilli: – Cytoplasmic projection from epithelia cells – Increase membrane surface area for increased absorption and/or secretion

Transitional epithelium Description: – Appearance is variable ( transitional), shape of cells in apical layer ranges from squamous (when stretched) to cuboidal (when relaxed)

Location: – Lines urinary bladder and portions of ureters and urethra

Cognitive exercise…..

Q?? Q1.

A D

Q2.

B

E

Z C

What type of epithelial tissues illustrated in AF?

F

What is the structure labelled Z?

Goblet cell

Digestive tract: Jejunum

Esophagus

Stratified squamous epithelium

Which of the following is NOT a simple epithelium?

I

II

III

IV

X

MORE exercise Q1. List the epithelial type that is found: (c) Lining the lumen of the stomach (e) Lining the tiny air sacs of the lungs, •

epithelial cell lining the wall of the alveolus

(f) Lining the trachea (wind pipe)

Specialized epithelial cell: Glands Exocrine and Endocrine glands

Specialized epithelial cell Glands classified into TWO categories: (2)Exocrine (3)Endocrine • Exocrine: (invaginated epithelium) secrete non-hormonal substances through a narrow tube (duct), into a body cavity or the surface of their epithelial origin E.g. sweat glands, sebaceous glands,

• Endocrine: lack ducts, secrete hormones, their secretory products are released directly into the bloodstream, the lymphatic system, or interstitial fluid (tissue fluid) • Major endocrine glands of the body: E.g. Adrenal, pituitary, thyroid, parathyroid, and pineal glands, ovaries, placenta and testes – Hormones secreted by endocrine glands include: peptides/proteins, modified a.a., steroids and glycoproteins – The secretory cells organized in cords of cells or in a follicular arrangement (follicular cells: Form follicles that surround a cavity, stored hormone is released upon receiving a release signal)

Exocrine glands are classified according to (2) nature of their secretion (3) mode of secretion (4) number of cells (unicellular or multicellular)

Exocrine glands: Nature of secretion In many exocrine glands (digestive, respiratory systems), secrete substances describes as: •

Mucous glands: thick, viscous, gel-like protective lubricant, called mucus, – − −

Line the body cavity, open to the outside of the body lubricates the tissue, protects from drying Goblet cells, salivary glands

(2) Serous glands: secrete enzyme-rich watery fluid – − −

Line a body cavity, does NOT open to the outside of the body Pleural membranes lining the lung cavity Pericardial membrane lining the pericardial cavity

(3) Mixed glands: A mixture of the two type

Exocrine glands: Modes of secretion Three different mechanisms for releasing their secretory products: • Merocrine glands: • The release of the secretory product occurs via exocytosis. Neither cell membrane nor cytoplasm becomes a part of the secretion (E.g. parotid gland, a type of salivary gland) (3) Apocrine glands: • A small portion of the apical cytoplasm is released along with the secretory product (E.g. Lactating mammary gland) (4) Holocrine glands:

(E.g. sebaceous gland)

(E.g. parotid gland, a type of salivary gland)

(E.g. Lactating mammary gland)

Secretio n Secretory vesicle Golgi complex RER Nucleu s

Pinche d off portion of cell is secreti on

Mature cell dies and becomes secretory product Cell division replaces lost cell

Exocrine glands: Number of cells Glands – Unicellular, >E.g. mucus-secreting goblet cells (simplest) of the trachea – Multicellular, > consist of clusters of secretory cells > E.g. Those secrete saliva, sweat, milk

Exocrine/ Endocrine?

Unicellular Exocrine gland

Unicellular/ Multicellular ?

Exocrine gland

Simple gland

Compound gland

Functions of epithelial cells is specialized for (1) Movement of materials in, out or around the body (2) Protection of the internal environment against the external environment (3) Secretion of a product

• PHYSICAL PROTECTION:

– provides physical protection from abrasion, dehydration, and damage by xenobiotics.

• MOVEMENT IN AND OUT OF THE BODY:

– It controls permeability of a substance in its effort to enter or leave the body. – Some epithelia are relatively impermeable; others are readily crossed. – This epithelial barrier can be damaged in response to various toxins.

• SECRETION:

– Contains glands and secrets substances such as sweat or digestive enzymes. – Others secrete substances into the blood (hormones), such as the pancreas, thyroid, and pituitary gland.

Main characteristics of epithelium 1. Rest on a basement membrane – –

Supports the epithelium, separate it from the underlying c.t., Forms a type of barrier, (prevent the spread of malignant cells into underlying c.t.

2. Little intercellular – –

Pack close together, with a very small intercellular space Differ from c.t., c.t. cells separated by a large intercellular space

3. Avascular –

Epithelium derives its nutrition by diffusion of tissue fluid from the vessels in the underlying c.t.

4. Derive from all three germ layers – – –

E.g. ectoderm give rise to the epithelium of the skin (and associated glands), mouth and anus Mesoderm: Endothelium of bv, and lymph vessels, pleura, pericardium Endoderm: Esophagus, stomach, intestines

(2) Connective tissue

Connective tissue Divided into two major classes: Connective tissue proper Special connective tissue

Connective tissue • Connective tissue proper • Ground substance and fibers • Connective tissue fibers: Collagen, Elastic (dense) , Reticular (loose)

– Loose (areolar) connective tissue: – Dense (fibrous) connective tissue • Specialized connective tissue – Cartilage, bone and blood

“Connective tissues are specialized to provide support and hold the body tissues together (they connect).”

Connective tissue functions as…..

• Connective tissue serves many purposes in the body: (1) (2) (3) (4) (5) (6)

binding supporting protecting forming blood storing fats filling space

Loose connective tissue • Loose connective tissue – binds epithelia to underlying tissues – functions as “packing material”, holding tissues or organ in place. – Consists of cells scattered within the extracellular matrix (ECM) – EXTRACELLULAR MATRIX: an amorphous mass of proteins that form a ground substance, which is strengthened by a loose scattering of protein (C.T.) fibers, such as collagen fibers, elastic fibers and reticular fibers.

Types of Collagen fibers – (1) Collagen fibers: >provide strength and flexibility, dominant type of c.t., >appear as thick bundles (DENSE a.k.a FIBROUS C.T.) – (2) Elastic fibers: >long thread made of proteins, elastin; > stretchable structure, expand and return to their original sizes > lung tissue and wall of the blood vessel – (3) Reticular fibers: >fine networks, thin and branched >gave support to individual cells, E.g. liver, muscle, adipose

A mixture of connective tissue fibers: Collagen and elastic fibers intermingle in the dermis

Loose (areolar) c.t.

Dense (fibrous) connective tissue

• The cells that secrete collagen and other fibrous proteins are known as fibroblast. • Contains other cells: e.g. Macrophages, mast cells, fat (adipose) cells

Function: Provides support, reservoir for fluid and salts and nourishment for epithelium. Location: Beneath skin, between organs Cells: Fibroblast, macrophages, mast cells

Loose (areolar)

Adipose tissue • Fat cells (adipocytes) are found in loose connective tissue, usually in large groups, referred, as adipose tissue. • FUNCTIONS: insulates the body and stores fuel as fat molecules. Do you know??? Each adipose cell contains a large fat droplet that swells when fat is stored and shrinks when the body uses fat as fuel.

Loose connective tissue : Adipose tissue • Fat is stored in globules of adipose tissue, a type of connective tissue. • As a person gains or loses weight, the sizes of the fat globules increases or decreases. A person cannot decrease the number of fat cells by losing weight.

Dense (fibrous) connective tissue • Fibrous connective tissue – Is dense, owing to its large number of collagenous fibers. – Forms… • Tendons (connects muscle to bone) • Ligaments (join bones to bones and together at joints)

Function: Provide flexible, strong connections Location: Tendons, ligaments, dermis of skin Cells: Fibroblast

Dense (fibrous) connective tissue

All connective tissues do share a common structural feature: They all have abundant extracellular matrix because their cells are spaced widely apart. e.g. In bone, the extracellular matrix contains crystals that make the bones hard. In blood, the extracellular matrix is

Specialized c.t. >Cartilage • Cartilage – Has an abundance collagenous fibers embedded in a rubbery matrix. – The rubbery matrix > a protein-carbohydrate complex called chondroitin sulfate – Chondroitin sulfate and collagenous fibers (collagen) are secreted by cells called chondrocytes – Avascular – Many vertebrates have cartilaginous skeletons during the embryo stage, but most of the cartilage is replaced by bone as embryo matures. – Cartilage is retained in certain locations, such as the discs (act as cushions between vertebrae and the caps on the end of some bones). – Allows to absorb considerable physical impact without breaking.

Cartilage • Function – Provides flexible support, shock absorption and reduction of friction on load-bearing surfaces

• Location – Trachea, spinal disc, knees, joints, ear, nose

• Cell – Chondrocytes

Specialized c.t. >Bone • A mineralized connective tissue. • Bone forming cells are called osteoblasts. • Osteoblasts: deposit a matrix of collagen. • Calcium, magnesium and phosphate ions combine and harden within the matrix into the mineral hydroxyapatite. • Consists of repeating unit called osteon (Haversian system). • Each osteon has concentric layers of mineralized matrix surrounded a central canal containing blood vessels and nerves.

Bone • Function – Protects internal organs; provides rigid support for muscle attachment • Location – Most of skeleton • Cells: – Osteocytes

Bone matrix and bone cells Organic material

– The family of bone cells: Osteoblast, Osteocytes, Osteoclasts Osteoid (ground substance and collagen fibers)

Inorganic material

– Hydroxyapatites (calcium phosphate crystal)

Specialized c.t. >Blood • The matrix is a liquid called plasma. • Function – As highway of immune system and primary means of communication between organs

• Location – Circulatory system

• Cells Erythrocytes (carry oxygen), Leukocytes (function in the immune system) Plasma/thrombocytes (blood clotting)

(3) MUSCLE TISSUE Skeletal muscle Cardiac muscle Smooth muscle

Muscle tissue:

skeletal muscle

• Function – Voluntary movement • Location – Skeletal muscle • Cell: – Skeletal muscle cells/ muscle100fiber µm Multiple nuclei

Muscle fiber

Sarcomere

Skeletal muscle • Usually attached by tendons to bones, so that, when the muscle contract, they cause the bones to move at their joints. • Each skeletal muscle contains numerous muscle fibers (a single muscle cell muscle fiber). • Each muscle fiber enclose a bundle of myofibrils. • Each myofibril is composed of thick and thin myofilaments. • Each muscle fiber is multinucleate (having long, multinucleate cells running the length of the muscle)

Muscle tissue:

cardiac muscle

• Striated, branched, responsible for the contraction of the heart (involuntary) • Function – Highly interconnected cells, promotes rapid spread of signal initiating contraction • Location Walls of heart • Cell Cardiac muscle cells

Intercalated Nucleus disk

50 µm

Cardiac muscle • Cardiac muscle is composed of smaller, interconnected cells, each with a single cells. • The interconnections between adjacent cells (appeared under the microscope as dark lines) called intercalated discs. • These interconnections enable the cardiac muscle cells to form a single, functioning unit known as myocardium. • Certain cardiac muscle cells generate electric impulses spontaneously, and these impulses spread across, from cell to cell, causing all of the cells in the myocardium

Muscle tissue:

smooth muscle

• Smooth muscle (lack striations) • Function – Involuntary contraction commanded by the central nervous system – Such as churning of the stomach and constriction of arteries •Location Walls of blood vessels, stomach and intestines •Cell Smooth muscle cells

Nucleus Muscle fibers

25 µm

Smooth muscle cells

Muscle tissue:

smooth muscle

• Found in the organs of the internal environment, or viscera (sometimes known as visceral muscle). • Smooth muscle tissue consists of sheets of long, spindle-shaped cells, each cells containing a single nucleus.

Muscle Tissues

(4) Nerve tissue

Four distinct parts: • dendrites, (2) the cell body, (3) the axon and (4) the

Nerve tissue • Contains two main cell types: – Neurons (nerve cells) and neuroglia/ glial cells or supporting cells. • Function (Neurons) – To produce and conduct electrochemical events or “impulses”. Each neuron consists of FOUR parts:, dendrites, cell body, axon and synaptic terminal. Neuroglia do NOT conduct electrical impulses but instead, •Support and insulate neurons (form an insulating covering: myelin sheath) •Eliminate foreign materials in and

Neurons Dendrite Nuclei of glial cells Axon

100 µm Fig. 38-3, p. 817

How does the structure of the neuron relate to its function?

Receive signals from other neuron Integrates the signal, coordinates metabolic activities

Action potentials starts here

Transmit signals to other neurons

nction: Receives and transmits information

Types of neurons (nerve cells) (1) Sensory neuron (2)Interneuron/ Association neuron (3) Motor neuron

Sensory neuron • Function – Carry impulses (info from internal or external environment) from sensory receptors to interneurons

• Location: – Eyes, ears, skin

• Characteristic cell types: – Rods and cones (eyes)

Interneuron • Function: –

Integrate information, conduct impulses between neurons in CNS

• Location: –

Locate in the brains and spinal cord

Motor neurons • Function: –

Carry impulses away from CNS, activate muscles or glands

• Location: –

Brain and spinal cord

SENSORY

INTERNEURON

MOTOR

MORE exercise Q2. What characteristic is common to all connective tissues??? Q3. What type of tissue contains a calcified ground substance and is specialized for structural support? ??

Organ systems • How many? (2) Integumentary system (3) Skeletal system (4) Muscular system (5) Nervous system (6) Endocrine system (7) Cardiovascular system (8) Immune/Lymphatic system (9) Respiratory system (10)Digestive system (11)Urinary system (12)Reproductive system

11 Organ Systems

Cont…… …..11 Organ Systems

THE END