chapter 05 histology - mrs. buck's biology site

©McGraw-Hill Education

Chapter 05

Histology


Ch. 5 Part 1: 5-1 & 5-2 Into To Tissues &

Epithelial Tissue (pgs 150-160)


Cells are Organized into Tissues In complex organisms, cells are organized into tissues

Tissues: Groups of similar cells with a common function

The study of tissues is called histology.

There are 4 major types of tissues in the body:

1. Epithelial tissue

2. Connective tissue

3. Muscle tissue

4. Nervous tissue


Table 5.2 - 4 Major Tissue Types

Type Function Location Distinguishing Characteristics

Epithelial Protection, secretion, absorption, excretion

Cover body surface, cover and line internal organs, compose glands

Lack blood vessels, cells readily divide, cells are tightly packed

Connective Bind, support, protect, fill spaces, store fat, produce blood cells

Widely distributed throughout the body

Mostly have good blood supply, cells are farther apart than epithelial cells, with extracellular matrix in between

Muscle Movement Attached to bones, in the walls of hollow internal organs, heart

Able to contract in response to specific stimuli

Nervous Conduct impulses for coordination, regulation, integration, and sensory reception

Brain, spinal cord, nerves Cells communicate with each other and other body parts


Figure 5.1 Intercellular Junctions

Tight junctions: • Membranes of adjacent cells merge and fuse

• Located among cells that form linings, sheet-like layers

• Blood-brain barrier

Desmosomes: • Form “spot welds” between cells

• Structural reinforcement

• Located among outer skin cells

Gap junctions: • Tubular channels between cells

• Molecules can move between cells

• Located in cardiac muscle cells


Table 5.1 Types of Intercellular Junctions

Type Characteristics Example

Tight junctions Close space between cells by fusing cell membranes

Cells that line the small intestine

Desmosomes Bind cells by forming “spot welds” between cell membranes

Cells of the outer skin layer

Gap junction Form tubular channels between cells that allow exchange of substances

Muscle cells of the heart and digestive tract


From Science to Technology 5.1 Nanotechnology Meets the Blood-Brain Barrier

Nanotechnology helps with drug delivery across the blood-brain barrier

Blood-brain barrier selects which chemicals are allowed to cross; protects from toxins & chemical fluctuations

Nanotechnology uses structures smaller than 100 nm in at least 1 direction, to help medications cross the barrier

Example: Anesthetics or chemotherapeutics are combined with liposomes (phospholipid bubbles) to mask portion of drug that cannot cross the barrier

Example: Insulin can be inhaled in nanoparticles, instead of being injected


Epithelial Tissue General Characteristics:

• Covers organs and body surface

• Lines cavities and hollow organs

• Makes up glands

• Have a free surface on outside, and basement membrane on inside

• This tissue lacks blood vessels (avascular) and nutrients diffuse to

epithelial tissue from underlying connective tissue

• Cells readily divide; injuries heal rapidly

• Cells are tightly packed

• Classified according to cell shape and number of cell layers

• Shapes: squamous (flat), cuboidal (cube-shaped), columnar (tall)

• Layers: simple (one layer of cells), stratified (2 or more layer of

cells), or pseudostratified (appears layered, but is not)


Figures 5.3 and 5.4 Epithelial Tissue Types

Simple squamous:

• Single layer of thin, flat cells

• Substances pass easily through air sacs (alveoli) & capillaries

• Thin & delicate, can be damaged

• Found in diffusion & filtration sites

• Lines air sacs (alveoli) & capillaries

• Lines blood & lymphatic vessels

Simple cuboidal:

• Single layer of cube-shaped cells

• Secretion and absorption

• Lines kidney tubules, thyroid follicles

• Covers ovaries

• Lines ducts of some glands

Top: b-c: © McGraw-Hill Education/Al Telser, photographer.

Bottom: b: © Victor P. Eroschenko



Simple columnar:

• Single layer of elongated cells

• Nuclei usually at same level,

near basement membrane

• Sometimes have cilia

• Sometimes have microvilli

• Sometimes have goblet cells

(secrete mucus)

• Secretion and absorption

• Lines uterus, stomach, intestines

Pseudostratified columnar: • Single layer, but appears layered

• Nuclei at 2 or more levels

• Cells vary in shape

• Often has cilia, goblet cells

• Protection from infection

• Lines respiratory passageways

Top: b: © Victor P. Eroschenko

Bottom: © McGraw-Hill Education/Dennis Strete



Stratified squamous: • Many cell layers; thick

• Protective layer

• Outermost cells are flat

• Deeper cells are cuboidal

• New cells form, push older cells

toward free surface

• Outer layer of skin (keratinized)

• Lines oral cavity, vagina, anal canal

Stratified cuboidal: • 2-3 layers of cube-shaped cells

• More protection than 1 layer

• Lines ducts of mammary, sweat,

& salivary glands, and pancreas

Top: © McGraw-Hill Education/Al Telser, photographer

Bottom: © McGraw-Hill Education/Al Telser, photographer



Stratified columnar: • Top layer of elongated cells

• Cube-shaped cells in

deeper layers

• Lines part of male urethra,

ducts of exocrine glands

Transitional (uroepithelium): • Many cell layers

• Cube-shaped and elongated

cells

• Changes shape with increased

tension; stretches

• Line urinary bladder, ureters,

and part of urethra

Top: b: © McGraw-Hill Education/Al Telser, photographer

Bottom: b,d: © Ed Reschke


Glandular Epithelium

Glandular Epithelium: Composed of cells that produce and

secrete substances into ducts or body fluids

There are 2 types of glands:

• Endocrine glands secrete into tissue fluid or blood

• Exocrine glands secrete into ducts that open onto surface

2 structural types of exocrine glands:

• Unicellular: Composed of one cell, such as a goblet cell

(secretes mucus)

• Multicellular:

• Composed of many cells

• Sweat glands, salivary glands, etc.

• Simple or compound


Figure 5.12 Structural Types of Exocrine Glands

Simple: duct does not branch

Compound: duct branches before it reaches secretory portion

Tubular: consist of epithelial-lined tubes

Alveolar: terminal portions form sac-like dilations


Table 5.3 Types of Exocrine Glands

Type Characteristics Example

Unicellular A single secretory cell Mucous-secreting cell (see Fig. 5.5)

Multicellular Glands that consist of many cells

Simple glands Glands that communicate with the surface by means of ducts that do not branch before reaching the secretory portion

1. Simple tubular gland Straight tube-like gland that opens directly onto surface

Intestinal glands of small intestine (see Fig. 17.3)

2. Simple branched tubular gland Branched, tube-like gland; duct short or absent Gastric glands (see Fig. 17.19)

3. Simple coiled tubular gland Long, coiled, tube-like gland; long duct Merocrine (sweat) glands of skin (see Figs. 6.10 and 6.11)

4. Simple branched alveolar gland Secretory portions of gland expand into saclike compartments along duct

Sebaceous gland of skin (see Fig. 5.14)

Compound glands Glands that communicate with surface by means of ducts that branch repeatedly before reaching the secretory portion

1. Compound tubular gland Secretory portions are tubules extending from branches of branches that combine into one duct

Bulbourethral glands of male (see Fig. 22.4)

2. Compound alveolar gland

Secretory portions are irregularly branched tubules with numerous saclike outgrowths

Mammary glands (see Fig. 23.28)


Figure 5.13 Types of Glandular Secretion

Merocrine glands: Secrete fluid products by exocytosis; salivary & sweat

glands, pancreas

Apocrine glands: Lose small part of cell during secretion; mammary &

ceruminous glands

Holocrine glands: Release entire cells filled with product; sebaceous glands


Table 5.5 Epithelial Tissues Type Description Function Location

Simple squamous epithelium Single layer, flattened cells

Filtration, diffusion, osmosis, covers surface

Air sacs of lungs, walls of capillaries, linings of blood and lymph vessels, part of the membranes lining body cavities and covering viscera

Simple cuboidal epithelium Single layer, cube-shaped cells

Protection, secretion, absorption Surface of ovaries, linings of kidney tubules, and linings of ducts of certain glands

Simple columnar epithelium Single layer, elongated cells

Protection, secretion, absorption Linings of uterus, stomach, and intestines

Pseudostratified columnar epithelium

Single layer, elongated cells

Protection, secretion, movement of mucus and substances

Linings of respiratory passages

Stratified squamous epithelium

Many layers, top cells flattened

Protection Superficial layer of skin and linings of oral cavity, vagina, and anal canal

Stratified cuboidal epithelium 2 or 3 layers, cube-shaped cells

Protection Linings of ducts of mammary glands, sweat glands, salivary glands, and pancreas

Stratified columnar epithelium

Top layer of elongated cells, lower layers of cube-shaped cells

Protection, secretion Part of the male urethra and lining of larger ducts of excretory glands

Transitional epithelium Many layers of cube-shaped and elongated cells

Stretchability, protection Inner lining of urinary bladder and linings of ureters and part of urethra

Glandular epithelium Unicellular or multicellular

Secretion Salivary glands, sweat glands, endocrine glands


Ch. 5 Part 2: 5-3 Connective Tissue (pgs 160-170)


Connective Tissues General characteristics:

Most abundant tissue type

Cells are farther apart than epithelial cells; contain matrix between cells

Many functions:

• Bind structures together

• Provide support and protection

• Serve as frameworks

• Fill spaces

• Store fat

• Produce blood cells

• Protect against infections

• Help repair tissue damage

Extracellular matrix consists of protein fibers and ground substance; consistency varies from

fluid to semisolid to solid

Most have good blood supply, and are well-nourished, but vascularity varies among tissue types

Most cells can divide


Clinical Application 5.1 The Body’s Glue: The Extracellular Matrix

Functions of normal extracellular matrix (ECM):

• scaffolding that organizes & anchors cells into tissues

• relays chemical signals that control cell division and differentiation, tissue repair, cell migration

Cancer: Can convert fibroblasts into myofibroblasts, which take on characteristics of cancer cells; also loosens fibroblast connections, allowing migration of converted fibroblasts and spreading cancer

Liver Fibrosis: Collagen deposition increases, and ECM now exceeds its normal 3% of organ. Damaging agents evoke normal inflammatory response, but if it continues too long, it can block connection between liver cells and blood, perhaps leading to cirrhosis.

Heart Failure and Atherosclerosis: Some forms involve excess collagen deposition, which can stiffen the heart or block blood flow


Figures 5.15 and 5.16 Major Cell Types of Connective Tissue

Fibroblasts:

• Most common fixed cell

• Large star-shaped cell

• Secrete fibers into extracellular matrix

Macrophages (Histiocytes):

• Usually attached to fibers, but can detach

and wander

• Conduct phagocytosis

• Defend against infection

Top: © Juergen Berger/Science Source

Bottom: © Biology Pics/Science Source


Figures 5.17 Major Cell Types of Connective Tissue

Mast Cells: • Large cells

• Release heparin to prevent

blood clotting

• Release histamine, which

• causes inflammatory response

© Steve Gschmeissner/Science Source


Figure 5.18 Connective Tissue Fibers Fibroblasts produce 3 types of fibers in connective tissue:

1. Collagen Fibers: • Thick threads of collagen, the body’s main structural protein

• Great tensile strength and flexible, slightly elastic

• Found in ligaments and tendons

2. Elastic (Yellow) Fibers: • Composed of elastin protein; branching

• Can stretch and return to original shape

• Not as strong as collagen fibers

• Found in vocal cords, respiratory air

passages

3. Reticular Fibers: • Thin, branching fibers of collagen

• Form delicate, supporting networks

• Found in spleen, liver

© Prof. P. Motta/Univ. “La Sapienza”/Science Source


Table 5.6 Components of Connective Tissue

Component Characteristics Function

Cellular

Fibroblasts Widely distributed, large, star-shaped cells

Secrete proteins that become fibers

Macrophages Motile cells sometimes attached to fibers Clear foreign particles from tissues by phagocytosis

Mast cells Large cells, usually located near blood vessels

Release substances that may help prevent blood clotting (heparin) and promote inflammation (histamine)

Extracellular Matrix

Collagen fibers (white fibers) Thick, threadlike fibers of collagen with great tensile strength

Hold structures together

Elastic fibers (yellow fibers) Bundles of microfibrils embedded in elastin

Provide elastic quality to parts that stretch

Reticular fibers Thin fibers of collagen Form delicate supportive networks within tissues

Ground substance Nonfibrous protein and other molecules, and varying amounts of fluid

Fills in spaces around cells and fibers


Clinical Application 5.2 Abnormalities of Collagen

Collagen makes up >60% of the protein in bone and cartilage, and a large percentage of dry weight of skin, tendons, ligaments

Has a very precise structure, and is vulnerable to disruption

Examples:

• Chondrodysplasia: Collagen chains are asymmetric and

too wide, causing stunted growth and deformed joints

• Marfan syndrome: Deficiency of the protein fibrillin; leads to long limbs, spindly fingers, sunken chest, weak aorta,

dislocation of the lens of the eye


Categories of Connective Tissue Connective tissues can be classified in 2 major categories:

Connective Tissue Proper:

Loose connective tissues:

• Areolar

• Adipose

• Reticular

Dense connective tissues:

• Dense Regular

• Dense Irregular

• Elastic

Specialized connective tissues:

Cartilage

Bone

Blood


Figures 5.19 and 5.20 Connective Tissue Types


Bottom: b: © McGraw-Hill Education/Al Telser, photographer

Areolar Connective Tissue:

• Forms thin, delicate membranes

• Cells are mainly fibroblasts

• Gel-like ground substance

• Collagenous & elastic fibers

• In subcutaneous layer

• Beneath most epithelia, where

it nourishes nearby epithelial cells

Adipose Tissue:

• Adipocytes store fat

• Push their nuclei to one side

• Crowd out other cell types

• Cushions and insulates

• Beneath skin (subcutaneous layer)

• Behind eyeballs

• Around kidneys and heart

• Spaces between muscles



Reticular Connective Tissue:

• Composed of thin reticular fibers

• Supports walls of internal organs

• Walls of liver, spleen

Dense Regular Connective Tissue:

• Closely packed collagenous fibers

• Fine network of elastic fibers

• Most cells are fibroblasts

• Very strong, withstands pulling

• Binds body parts together

• Tendons, ligaments, dermis

• Poor blood supply; slow to heal


Bottom: b: © McGraw-Hill Education/Dennis Strete



Top: © Victor P. Eroschenko

Bottom: © McGraw-Hill Education/Al Telser, photographer

Dense Irregular Connective Tissue:

• Randomly organized, thick,

interwoven collagenous fibers

• Can withstand tension exerted

from different directions

• Dermis of skin

• Around skeletal muscles

Elastic Connective Tissue:

• Abundant yellow elastic fibers

• Some collagenous fibers

• Fibroblasts

• Attachments between bones

of spinal column

• Walls of hollow organs, such

as large arteries, airways

• Parts of heart

• Elastic quality, stretches


Connective Tissue Types

Cartilage:

• A rigid, specialized connective tissue

• Support, framework, attachments

• Protection of underlying tissue

• Models for developing bone

• Matrix contains collagen in gel-like ground substance

• Chondrocytes (cartilage cells) in lacunae (chambers), surrounded

by matrix

• Lacks blood supply; heals slowly

• Covered by perichondrium (connective tissue), which provides

some nutrients to the cartilage

• 3 types of cartilage: Hyaline, Elastic, and Fibrocartilage



Hyaline cartilage:

• Most common type

• Fine collagen fibers

• Ends of bones in joints

• Nose, respiratory

passages

• Embryonic skeleton

Elastic cartilage:

• Flexible, due to elastic

fibers in matrix

• External ear, larynx




Figure 5.27 Connective Tissue Types

Fibrocartilage:

• Very tough, due to many collagenous fibers

• Shock absorber

• Intervertebral discs

• Pads of knee and pelvic girdle

b: © Victor P. Eroschenko


Bone (Osseous Tissue):

• Most rigid connective tissue

• Solid matrix, composed of mineral (Ca) salts & collagen

• Supports structures

• Protects vital structures

• Produces blood cells

• Stores & releases Ca, P

• Attachment sites for muscles

• Forms skeleton

• Contain osteocytes (bone cells) in lacunae

• 2 types: compact and spongy

Connective Tissue Types


Figure 5.28 Connective Tissue Types Compact Bone:

• Osteoblasts deposit matrix in lamellae (layers)

• Lamellae occur in rings around central canals

• Osteocytes + matrix + central canal form cylindrical units called

Osteons:

• Osteons are cemented together to form compact bone

• Central canals contain blood vessels; bone is well-nourished, heals more quickly than cartilage

b: © McGraw-Hill Education/Sennis Strete, phototgrapher. c: © Prof. P. Motta/Univ. “La Sapienza”/Science Source


Figure 5.29 Connective Tissue Types

Blood:

• Cells suspended in fluid matrix called plasma

• Red blood cells transport gases

• White blood cells defend again infection

• Platelets help in blood clotting

• Transports substances around body

b: © McGraw-Hill Education/Dennis Strete, photographer


Table 5.7 Connective Tissues Type Description Function Location

Areolar connective tissue

Cells in fluid-gel matrix Binds organs Beneath the skin, between muscles, beneath epithelial tissues

Adipose tissue Cells in fluid-gel matrix Protects, insulates, stores fat Beneath the skin, around the kidneys, behind the eyeballs, on the surface of the heart

Reticular connective tissue

Cells in fluid-gel matrix

Supports Walls of liver and spleen

Dense regular connective tissue


Binds body parts Tendons, ligaments

Dense irregular connective tissue


Sustains tissue tension In the deep layer of skin

Elastic connective tissue

Cells in fluid-gel matrix Provides elastic quality Connecting parts of the spinal column, in walls of arteries and airways

Hyaline cartilage Cells in solid-gel matrix Supports, protects, provides framework

Ends of bones, nose, and rings in walls of respiratory passages

Elastic cartilage Cells in solid-gel matrix Supports, protects, provides flexible framework

Framework of external ear and part of larynx

Fibrocartilage Cells in solid-gel matrix Supports, protects, absorbs shock

Between bony parts of spinal column, parts of pelvic girdle, and knee

Bone Cells in solid matrix Supports, protects, provides framework

Bones of skeleton, middle ear

Blood Cells and platelets in fluid matrix

Transports gases, defends against disease, clotting

Throughout the body in a closed system of blood vessels and heart chambers


5-4 Types of Membranes & Muscle/Nervous Tissue

(pgs 171-173)


Types of Membranes (1) Membranes are sheets of cells

Epithelial membranes are composed of epithelial and connective tissue; cover body surfaces and line cavities

3 types of epithelial membranes:

1. Serous membranes:

• Line body cavities that do not open to outside of body

• Inner linings of thorax and abdomen; covers organs

• Simple squamous epithelium + areolar connective tissue

• Secrete serous fluid for lubrication, reducing friction

2. Mucous membranes:

• Line cavities and tubes that open to the outside of body

• Lining of digestive, respiratory, urinary, and reproductive tracts

• Epithelium + areolar connective tissue

• Goblet cells secrete mucus


Types of Membranes (2)

3. Cutaneous membranes:

• Covers body surface

• Commonly called skin

• Part of integumentary system

4. Synovial membranes:

• Different from epithelial membranes

• Composed entirely of connective tissue

• Line joint cavities


Figure 5.30 Muscle Tissues General Characteristics:

• Muscle cells are also called muscle fibers

• Contractile; can shorten and thicken

• 3 types of muscle tissue: skeletal, cardiac, and smooth

Skeletal muscle tissue:

• Attached to bones

• Striated

• Voluntary

• Multinucleated cells

• Long cylindrical cells

• Stimulated by nerve cells

b: © McGraw-Hill Education/Al Telser


Figures 5.31 and 5.32 Muscle Tissues Smooth muscle tissue:

• Non-striated

• Spindle-shaped fibers

• Walls of hollow organs

• Walls of blood vessels

• Involuntary

Cardiac muscle tissue:

• Only in wall of heart

• Branching cells

• Involuntary

• Striated

• Intercalated discs




Figure 5.33 Nervous Tissue

Nervous tissues:

• Found in brain, spinal cord, peripheral nerves

• Main cells are neurons, which are specialized for communication,

via conduction of nerve impulses (sensory reception, motor control)

• Neurons coordinate, integrate, and regulate body functions

• Neuroglia support and nourish neurons

b: © McGraw-Hill Education/Al Telser, photographer


From Science to Technology 5.2

Tissue Engineering: Building a Replacement Bladder Donor organs are in short supply Tissue Engineering is showing promise for organ replacement, by growing cells or extracellular matrix from a person’s own cells or matrix, on a synthetic scaffold. No rejection by immune system Has already been used to provide skin, cartilage, bone, blood vessels Urinary bladders are being replaced by growing tissue donated by the patient Patient’s bladder tissue contains progenitor cells for smooth muscle and uroepithelium, which are used to grow a new bladder on a synthetic dome After implant, synthetic scaffold degenerates over time, leaving new bladder in place


Table 5.8 Muscle and Nervous Tissues

Type Description Function Location

Skeletal muscle tissue Long, thread-like cells, striated, many nuclei

Voluntary movements of skeletal parts

Muscles usually attached to bones

Smooth muscle tissue Shorter cells, single, central nucleus

Involuntary movements of internal organs

Walls of hollow internal organs

Cardiac muscle tissue Branched cells, striated, single nucleus

Heart movements Heart muscle

Nervous tissue Cells with cytoplasmic extensions

Sensory reception, release of neurotransmitter, and conduction of electrical impulses

Brain, spinal cord, and peripheral nerves

chapter 05 histology - mrs. buck's biology site

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