talk four: tissues, organs, and organ systems chapter 4 human biology (biol 104)

Talk Four:

Tissues, Organs, and Organ Systems

Chapter 4

Human Biology (BIOL 104)

Tissues, Organs, and Organ Systems

• Every year tens of thousands of people develop a disease or suffer an injury that severely damages an organ or tissue.

• If only it were possible to replace those body parts!

• All body cells come from “stem cells” (more in later talks).– Ah, back to the ethics stuff!!!!!

• Adults also have stem cells (less controversial)– Adult stem cells are more limited than embryonic cells– Active types show promise for regenerating cartilage

and heart muscle damaged by a heart attack

• We will focus on the basic types of cells and tissues that make up the Human Body.

Tissues• Tissue: – Similarly specialized cells that perform

a common function in the body.

• 4 main tissue types in the human body:

– 1. Epithelial: covers body surface and lines body cavities.

– 2. Connective: binds and supports body parts.

– 3. Muscular: Moves body parts

– 4. Nervous: Receives, interprets and sends signals.

1. Epithelial Tissue• This covers the whole surface of the body.

• It is made up of cells closely packed and ranged in one or more layers.– This tissue is specialized to form the covering or lining of

all internal and external body surfaces.

• Epithelial tissue that occurs on surfaces on the interior of the body is known as endothelium.

• Epithelial cells are packed tightly together, with almost no intercellular spaces and only a small amount of intercellular substance.

• Epithelial tissue, regardless of the type, is usually separated from the underlying tissue by a thin sheet of connective tissue; basement membrane.

• The basement membrane provides structural support for the epithelium and also binds it to neighboring structures.

1. Epithelial Tissue• 5 types:

• A: Squamous-flat-lungs and blood.

• B: Cuboidal-cube-kidney tubes.

• C: Columnar-pillars-Digestive tract.

• D: Pseudostratified ciliated columnar- Respiratory tract.

• E: Stratified squamous epithelium - esophagus Used with permission from imgarcade.com

Functions of Epithelial Tissue• Protection

– Epithelial cells from the skin protect underlying tissue from mechanical injury, harmful chemicals, invading bacteria and from excessive loss of water.

• Sensation– Sensory stimuli penetrate specialised epithelial cells.

Specialised epithelial tissue containing sensory nerve endings is found in the skin, eyes, ears, nose and on the tongue.

• Secretion– In glands, epithelial tissue is specialised to secrete

specific chemical substances such as enzymes, hormones and lubricating fluids.

• Absorption– Certain epithelial cells lining the small intestine absorb

nutrients from the digestion of food.

Functions of Epithelial Tissue• Excretion

– Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine. Sweat is also excreted from the body by epithelial cells in the sweat glands.

• Diffusion– Simple epithelium promotes the diffusion of gases, liquids and

nutrients. Because they form such a thin lining, they are ideal for the diffusion of gases (eg. walls of capillaries and lungs).

• Cleaning– Ciliated epithelium assists in removing dust particles and

foreign bodies which have entered the air passages.

• Reduces Friction– The smooth, tightly-interlocking, epithelial cells that line the

entire circulatory system reduce friction between the blood and the walls of the blood vessels.

Cleaning, an extended example - the Trachea

• Windpipe – connects larynx to primary bronchi.

• Held open by cartilage• Goblet cell

– Makes mucus

• Mucosa contains layer of pseudostratified ciliated epithelium– Sweep dirt and excess

mucus upwards

Basement Membrane• Why doesn't our skin fall completely off our bodies?

• The results of gravity's constant downward pull on our faces, shoulders, backs, necks, chests, organs, legs and feet are obvious to most of us, especially as we age.

• Nowhere is this more obvious than our skin. Millions of dollars are spent every year to tighten that sagging, drooping skin.

• The occasional face-lift, a little Botox, creams, serums, and muscle exercises are part of this nations obsession.

• Meet the basement membrane.– Epithelial Tissue is held to the body via a Basement membrane

Basement Membrane• The basement membrane serves as the

anchor for the epithelium, attaching it to the connective tissue below.

• Your skin has three layers. The outer layer, called the epidermis, is composed of epithelial cells.

• The middle layer is the dermis, and is composed of connective tissue such as– blood vessels, sweat glands, sebaceous

glands, and temperature sensors.

– The third layer is the subcutaneous, and is the lowest layer.

• The basement membrane lies between the epidermis and the dermis, keeping the outside layer tightly connected to the inside layer.

From the wikimedia free licensed media file repository

Basement Membrane• Not even the effects of gravity can

destroy this anchoring system. – While skin may droop and sag, it will

never completely fall off.

• Basement membrane is not found just in the skin. – It has important functions all over the

body.

• Any place you find epithelium and endothelium, the basement membrane will be sandwiched in between to hold the layers together.

• Basement membrane is composed of:– glycoproteins-sticky sugary proteins and

protein fibers:

• Collagen:– strong, elastic-stretchy From the wikimedia free

licensed media file repository

2. Connective Tissue• Supports, connects, or separates different types of

tissues and organs of the body.

• Contains high quantities of a protein called collagen

• Connective tissue proper consists of loose connective tissue and dense connective tissue (which is further subdivided into dense regular and dense irregular connective tissues.)

• Special connective tissue consists of reticular connective tissue, adipose tissue, cartilage, bone, and blood.

• Other kinds of connective tissues include fibrous, elastic, and lymphoid connective tissues.

2. Connective Tissue• Dense connective tissue

– In skin and capsules around organs – used as a support structure

• Adipose connective tissue– Mainly cells filled with fat- under

skin and kidneys – Energy reserve, insolation, and

padding

• Areolar connective tissue– Found under the skin – Elasticity

and diffusions of solutes

• Compact bone– Movement, support, and

protection

• Blood– Fluid blood plasma


Functions of connective tissue

• Storage of energy

• Protection of organs

• Provision of structural framework for the body

• Connection of body tissues

• Connection of epithelial tissues to muscle fiber.

• Supply of hormones all over the body

• Nutritional support to epithelium

• Site of defense reactions

• Repair of body tissues

Diseases of connective tissue• Scurvy – problems with sea

voyages, lack of food other than salted meats.

– Symptoms include, swollen gums, loose teeth, small black-and-blue spots on the skin, and bleeding from small blood vessels are among the characteristic signs of scurvy.

– Caused when vitamin C (ascorbic acid) is lost from diet

– Vitamin C is needed to keep Iron reduced in blood cells to carry oxygen

– In 1795, the British Royal Navy provided a daily ration of lime or lemon juice to all its men. English sailors to this day are called "limeys", for lime was the term used at the time for both lemons and limes.


Diseases of connective tissue

Marfan’s Syndrom and Ehler’s-Danlos syndromes - inherited disorder of connective tissue which affects many organ systems, including the skeleton, lungs, eyes, heart and blood vessels. All resulting from various mutation in collagen and other fibril associated proteins, ultimately affecting the structure and molecular interaction of connective tissue.

Several heritable diseases result from Several heritable diseases result from mutations in the collagenmutations in the collagen

3. Muscle tissue• Is a soft tissue that composes muscles in bodies, and gives

rise to muscles' ability to contract. This is opposed to other components or tissues in muscle such as tendons

• Muscle tissue varies with function and location in the body. In mammals the three types are:

• skeletal or striated muscle • smooth or non-striated muscle • cardiac muscle, which is sometimes known as semi-

striated

• Smooth and cardiac muscle contracts involuntarily, without conscious intervention.

Skeletal or striated muscle

• Striated in structure and under voluntary control, is anchored by tendons to bone and is used to effect skeletal movement such as locomotion and to maintain posture.

• An average adult male is made up of 42% of skeletal muscle and an average adult female is made up of 36% (as a percentage of body mass).


Smooth or non-striated muscle

• Smooth muscle, neither striated in structure nor under voluntary control, is found within the walls of organs and structures such as the:

• esophagus• stomach • intestines • bronchi• uterus • urethra • bladder• blood vessels • arrector pili in the skin (in

which it controls erection of body hair). From the wikimedia free licensed media

file repository

Cardiac Muscle• Cardiac muscle (myocardium),

found only in the heart, not subject to voluntary control.

• Cardiac "striated" in that they contain sarcomeres and are packed into highly regular arrangements of bundles; smooth muscle has neither.

• While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles (called intercalated discs).

• Heart cells must beat in unison. Intercalated Disks allow calcium to regulate united beating From the wikimedia free licensed media

file repository

4. Nervous Tissue• The main component of the

two parts of the nervous system; the brain and spinal cord of the central nervous system (CNS), and the branching peripheral nerves of the peripheral nervous system (PNS)

• Both regulate and control bodily functions and activity.

• It is composed of – neurons, or nerve cells,

which receive and transmit impulses

– neuroglia, also known as glial cells or more commonly as just glia.


4. Nervous Tissue• Glia assist the propagation of

the nerve impulse as well as providing nutrients to the neuron.

• Nervous tissue is made up of different types of nerve cells, all of which having an axon, the long stem-like part of the cell that sends action potential signals to the next cell.

• Functions of the nervous system are sensory input, integration, control of muscles and glands, homeostasis, and mental activity. From the wikimedia free licensed media

file repository

4. Nervous Tissue

Tissues require cell junctions

• Type of structure that exists within the tissue of some multicellular organisms, such as Humans.

• Consist of multiprotein complexes that provide contact between neighbouring cells or between a cell and the extracellular matrix.

• They also build up the paracellular barrier of epithelia and control the transport of solutes. Cell junctions are especially abundant in epithelial tissues.

• Cell junctions are especially important in enabling communication between neighboring cells via specialized proteins called communicating junctions. Cell junctions are also important in reducing stress placed upon cells.

Three types• A: Adhesion junction

• Cells within tissues and organs must be anchored to one another and attached to components of the extracellular matrix.

• Anchoring proteins extend through the plasma membrane to link cytoskeletal proteins in one cell to cytoskeletal proteins in neighboring cells as well as to proteins in the extracellular matrix

Three types• B: Tight junction

• Found in epithelia, they act as barriers that regulate the movement of water and solutes between epithelial layers.

• There is evidence to suggest that the structures in which solutes pass through are somewhat like pores.

• Prevent the highly acidic gastric fluid in your stomach from leaking out and digesting proteins of your own body instead of those you consume as food.

Three types• C: Communicating

(GAP) junctions

• Allow for direct chemical communication between adjacent cellular cytoplasm through diffusion without contact of the extra cellular fluid.

• Protrudes across the cell membrane, and when 2 adjacent cells interact, they form the gap junction channel.

• Play vital roles in the human body, including their role in the uniform contractile of the heart muscle.

• They are also relevant in signal

transfers in the brain, and their absence shows a decreased cell density in the brain.

• Retinal and skin cells are also dependent on gap junctions in cell differentiation and proliferation.

Organs and Organ Systems

• An organ is a collection of tissues joined in a structural unit to serve a common function

• Organs are composed of main tissue, parenchyma, and "sporadic" tissues, stroma.

• The main tissue is that which is unique for the specific organ, such as the specialized cells of the stomach,

• Sporadic tissues include the nerves, blood vessels, and connective tissues.

• Functionally related organs often cooperate to form whole organ systems.

• A hollow organ is a visceral organ that forms a hollow tube or pouch, such as the stomach or intestine, or that includes a cavity, like the heart or urinary bladder

Used with permission from imgarcade.com

Organ Systems• 1. Circulatory System: The main

function of this system is to transport nutrients and gasses to cells and tissues throughout body. This is accomplished by the circulation of blood.

• Cardiovascular: comprised of the heart, blood, and blood vessels. The beating of the heart drives the cardiac cycle which pumps blood throughout body.

• Cardiovascular organs: – heart, blood vessels, blood

• Lymphatic: This system is a vascular network of tubules and ducts that collect, filter, and return lymph to blood circulation.

• As a component of the immune system, the lymphatic system produces and circulates immune cells called lymphocytes.

• Lymphatic organs: – lymph vessels, lymph nodes,

thymus, spleen, tonsils


Organ Systems

• 2. Digestive System: This system breaks down food polymers into smaller molecules to provide energy for the body.

• Digestive juices and enzymes are secreted to break down the carbohydrates, fat, and protein in food.

• Primary organs: – mouth, stomach, intestines, rectum

• Accessory organs: – teeth, tongue, liver, pancreas

• 3. Endocrine System: This system regulates vital processes in the body including growth, homeostasis, metabolism, and sexual development. Endocrine organs secrete hormones to regulate body processes.

• Endocrine structures: – pituitary gland, pineal gland,

thymus, ovaries, testes, thyroid gland From the wikimedia free licensed media file

repository

Organ Systems

• 4. Integumentary System: This system protects the internal structures of the body from damage, prevents dehydration, stores fat and produces vitamins and hormones.

• Integumentary structures: – skin, nails, hair, sweat

glands

• 5. Muscular System: This system enables movement through the contraction of muscles.

• Structures: – muscles

Organ Systems

• 6. Nervous System: This system monitors and coordinates internal organ function and responds to changes in the external environment

• Structures: – brain, spinal cord, nerves

• 7. Reproductive System: This system enables the production of offspring through sexual reproduction.

• It is comprised of male and female reproductive organs and structures which produce sex cells and ensure the growth and development of offspring.

• Male organs: – testes, scrotum, penis, vas

deferens, prostate• Female organs:

– ovaries, uterus, vagina, mammary glands

Organ Systems

• 8. Respiratory System: This system provides the body with oxygen via gas exchange between air from the outside environment and gases in the blood.

• Respiratory organs: – lungs, nose, trachea,

bronchi

• 9. Skeletal System: This system supports and protects the body while giving it shape and form.

• Structures: – bones, joints, ligaments,

tendons, cartilageBoth diagrams used with permission from imgarcade.com

Organ Systems• 10. Urinary/Excretory

Systems: consists of the kidneys, ureters, urinary bladder, and urethra.

• The kidneys filter the blood to remove wastes and produce urine.

• The ureters, urinary bladder, and urethra together form the urinary tract, which acts as a plumbing system to drain urine from the kidneys, store it, and then release it during urination.

• Besides filtering and eliminating wastes from the body, the urinary system also maintains the homeostasis of water, ions, pH, blood pressure, calcium and red blood cells

• Structures: – kidneys, urinary bladder,

urethra, uretersUsed with permission from imgarcade.com

Organs and Organ

Systems

• It is important to keep in mind that these organ systems don't just exist as individual units.

• The final product of these cooperating systems is one unit called the body.

• Each system depends on the others, either directly or indirectly, to keep the body functioning normally.

Used with permission from imgarcade.com

The Skin: an example of an organ system

• The skin is the largest organ in the human body.

• For the average adult human, the skin has a surface area of between 1.5-2.0 square meters (16.1-21.5 sq ft.), most of it between 2–3 mm (0.10 inch) thick.

• On average it weighs about 9 pound

• The average square inch (6.5 cm²) of skin holds:

• 650 sweat glands• 20 blood vessels • 60,000 melanocytes• more than 1,000 nerve endings


• Skin performs the following functions:

• Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense;

• Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury

• Heat regulation: Dilated blood vessels increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.


• Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.– Loss of this function contributes

to the massive fluid loss in burns.

• Aesthetics and communication: Some trained professionals see our skin and can assess our mood, physical state and attractiveness.

• Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.


• Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.

• Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible".

• Water resistance: The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body.

Homeostasis• Homeostasis is the property

of a system in which variables are regulated so that internal conditions remain stable and relatively constant.

• Examples of homeostasis include the regulation of:– temperature – balance between acidity

and alkalinity (pH).

• It is a process that maintains the stability of the human body's internal environment in response to changes in external conditions.


talk four: tissues, organs, and organ systems chapter 4 human biology (biol 104)

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