Chapter 11: Human Organization

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Types of Tissues

• A tissue is composed of specialized cells that perform a function in the body.

• The human body has four major types of tissues:

• Epithelial tissue

• Connective tissue

• Muscular Tissue

• Nervous Tissue

• Cancers are classified by the type of tissue from which they arise:

• Carcinomas – cancers of epithelial tissue• Sarcomas – cancers of connective tissue• Leukemias – cancers of blood• Lymphomas – cancers of lymphatic tissue• Cancers are more likely to arise in tissues

in which cells divide rapidly.

Epithelial Tissue

• Epithelial tissue (epithelium) is made of highly packed cells that line the body surface and inner body cavities.

• Epithelial tissue functions in protection, secretion, absorption, excretion, and filtration.

• Epithelial tissue is classified according to cell type.

• Squamous epithelium is composed of flattened cells and is found lining the lungs and blood vessels.

• Cuboidal epithelium contains cube-shaped cells and is found lining the kidney tubules.

• Columnar epithelium has elongated cells with nuclei at the bottom of cells and is found in the digestive tract.

• Ciliated columnar epithelium is found lining the oviducts.

• Epithelial tissue is also classified according to the number of layers in a tissue.

• Simple means the tissue has a single layer of cells.

• Stratified means the tissue has layers of cells piled on top of one another.

• Pseudostratified means the epithelium appears layered but is not.

Simple squamous epithelium

Simple cuboidal epithelium

Simple columnar epithelium

Pseudostratified ciliated columnar epithelium

• A basement membrane joins epithelium to an underlying layer of connective tissue.

• Some epithelial cells are glandular and secrete a product.

• A gland may be a single cell or contain many cells.

• Mucus-secreting digestive glands are single goblet cells.

• Exocrine glands secrete products into ducts, while endocrine glands secrete directly into the bloodstream.

Junctions Between Epithelial Cells

• Junctions that occur between cells help cells function as a tissue.

• A tight junction forms an impermeable barrier between cells.

• A gap junction allows material to pass from one cell to the next.

• Adhesion junctions adhere cells together so tissues can stretch.

Connective Tissue

• Connective tissue binds organs together, provides support and protection, fills spaces, produces blood cells, and stores fat.

• Connective tissue cells are separated by noncellular matrix that ranges from solid to semifluid.

• The matrix houses fibers of three possible types.

•

• White collagen fibers contain the protein collagen; these fibers are flexible and strong.

• Reticular fibers are very thin, highly branched collagen fibers that form delicate supporting networks.

• Yellow elastic fibers contain the protein elastin; these fibers are more elastic and not as strong as collagen fibers.

Loose Fibrous and Dense Fibrous Tissues

• Loose fibrous and dense fibrous connective tissues have cells called fibroblasts in a matrix containing collagen and elastic fibers.

• Loose fibrous connective tissue supports epithelium and many internal organs.

• Dense fibrous connective tissue, packed with collagen fibers, is found in tendons and ligaments.

Loose fibrous connective tissue

Adipose Tissue and Reticular Connective Tissue

• In adipose tissue, fibroblasts enlarge and store fat to be used for energy, insulation, and organ protection.

• Adipose tissue is found beneath the skin and around certain internal organs.

• Reticular connective tissue forms the supporting meshwork of lymphoid tissue in lymph nodes, the spleen, thymus, and bone marrow.

Adipose tissue

Cartilage

• Cartilage cells lie in small chambers called lacunae separated by a solid but flexible matrix.

• Hyaline cartilage contains very fine collagen fibers and is found at the ends of bones, in respiratory passages, and in the nose.

• The fetal skeleton is made of hyaline cartilage and is replaced by bone.

Hyaline cartilage

• Flexible elastic cartilage has abundant elastic fibers and is found in the framework of the outer ear.

• Fibrocartilage has a matrix with strong collagen fibers.

• Fibrocartilage is found in structures that withstand tension and pressure, such as the pads between the vertebrae in the backbone and the wedges in the knee joint.

Bone• Bone is the most rigid connective tissue

with its matrix of calcium and other inorganic salts and protein fibers.

• Compact bone makes up the shafts of long bones and consists of cylindrical units called osteons.

• Osteons contain a central canal through which blood vessels carry blood and nutrients to bone tissue.

Compact bone

• In compact bone, cells lie within lacunae which are interconnected by tiny nutrient-delivering canals called canaliculi.

• The ends of long bones contain spongy bone.

• Spongy bone contains many bony bars and plates located along lines of stress, separated by irregular spaces.

• Spongy bone is strong yet lightweight.

Blood

• Blood is a fluid connective tissue containing blood cells in liquid plasma.

• Blood has many functions:• Keeps body chemistry within limits

• Transports nutrients and wastes to cells• Distributes heat

• Keeps pH and ions in balance• Protects against blood loss and disease

Blood, a fluid tissue

Components of Blood Plasma

• Inorganic ions: (electrolytes)

• Gases:• Plasma proteins:

• Organic nutrients:

• Nitrogenous wastes:

• Na+, Ca2+, K+, Cl2, HCO3-, HPO4

2+

• O2, CO2

• Albumins, globulins, fibrinogen

• Glucose, lipids, amino acids, phospholipids

• Urea, ammonia

• Formed elements of the blood include:• Red blood cells – small, biconcave, and

lacking nuclei, with hemoglobin that transports oxygen

• White blood cells – larger, nucleate, and fight infection and produce antibodies

• Platelets – fragments of larger cells that form a plug in damaged blood vessels, thus helping in the clotting process

Formed elements of blood

Muscular Tissue

• Muscular tissue is made up of cells called muscle fibers.

• All muscular tissue contains actin filaments and myosin filaments; the interaction of these accounts for movement.

• Three types of vertebrate muscle are skeletal, smooth, and cardiac.

• Skeletal muscle, under voluntary control, is attached by tendons to bones and allows for movement.

• Skeletal muscle fibers are long and cylindrical with many nuclei just inside the plasma membrane.

• Actin filaments and myosin filaments form a striated appearance in skeletal muscle.

Skeletal muscle

• Smooth (visceral) muscle is involuntary and nonstriated.

• Long, tapered cells, each with a single nucleus, form layers within the smooth muscle.

• Smooth muscle is found in the walls of the digestive tract and in blood vessels.

• Smooth muscle contracts more slowly than skeletal muscle but can remained contracted for a longer period.

Smooth muscle

• Cardiac muscle is found only in the walls of the heart and functions to pump blood.

• Cardiac muscle has striations but is involuntary.

• Cardiac muscle fibers are branched and have a single nucleus.

• Cells are bound end to end at intercalated disks, areas where plasma membranes between cells contain adhesion junctions and gap junctions.

Cardiac muscle

Nervous Tissue

• Nervous tissue found in the brain and spinal cord is made up of cells called neurons.

• Neurons have three parts:• Dendrites – carry impulses to the neuron

• Cell body – houses nucleus• Axon – carries impulse away from cell

• Axons are insulated with myelin; axons are bound together to form nerves.

• In addition to neurons, nervous tissue contains neuroglia, cells that support and nourish neurons.

• Three types of neuroglia are found in the brain:• Microglia support neurons and engulf

bacteria and cellular debris• Astrocytes provide nutrients and secrete a

hormone called glia-derived growth factor• Oligodendrocytes form myelin.

A neuron and some types of neuroglia

Body Cavities and Body Membranes

• The human body is divided into the ventral cavity and the dorsal cavity.

• During development, the coelom becomes the ventral cavity, which is divided into thoracic and abdominal cavities.

• The thoracic cavity contains the pleural cavities each containing a lung, and the pericardial cavity housing the heart.

Mammalian body cavities

• The thoracic cavity is separated from the abdominal cavity by the diaphragm.

• The upper abdominal cavity contains the stomach, liver, spleen, gall bladder, and most of the intestines.

• The lower abdominal cavity contains the rectum, urinary bladder, and the rest of the large intestine.

• The dorsal cavity contains the cranial cavity that houses the brain, and the vertebral canal that contains the spinal cord.

Body Membranes• Here the term “membrane” refers to a thin

lining of epithelium overlying a layer of loose connective tissue.

• Body membranes line cavities and internal spaces of organs and tubes that open to the outside.

• There are mucous membranes, serous membranes, synovial membranes, and meninges.

• Mucous membranes line the tubes of digestive, respiratory, urinary, and reproductive systems.

• Mucus secreted by goblet cells in the epithelial layer of mucous membrane protects the body from invasion by bacteria and viruses.

• Mucus also protects the lining of the stomach from digestive juices.

• Serous membranes line the thoracic and abdominal cavities and the organs they contain and secrete a watery fluid that lubricates the membranes.

• Serous membranes have specific names according to their location:

• Pleura - line pleural cavity and cover lungs• Pericardium - lines pericardial cavity and

covers heart• Peritoneum - lines abdominal cavity where

it forms a double-layered mesentery.

• Synovial membranes line freely movable joint cavities.

• They secrete lubricating synovial fluid into the joint cavity that helps bones move freely.

• The meninges are membranes in the dorsal cavity that protect the brain and spinal cord.

• Meninges are composed of connective tissue only.

Organ Systems• Organs work together in organ systems;

all body organ systems work together.• A single organ may be part of more than

one organ system.• The integumentary system is made up of

the skin, including an outer epidermis and an inner dermis.

• Skin covers and protects the body, houses sensory receptors, and helps in temperature regulation.

• The integumentary system includes nails, glands, sensory receptors, and hairs.

• The digestive system consists of the mouth, esophagus, stomach, small intestine, and large intestine along with associated organs.

• The digestive system receives and breaks down food into nutrient molecules that are distributed to cells.

• The cardiovascular system, made up of the heart and blood vessels, distributes nutrients, oxygen, and heat throughout the body, and helps to remove wastes.

• The lymphatic system consists of lymphatic vessels that transport lymph, lymph nodes, and other lymphoid organs,

• This system helps protect again disease by producing and storing lymphocytes, collects excess tissue fluid, and absorbs fats from digestion.

• The immune system consists of all body cells that protect against disease.

• The respiratory system consists of the lungs and branched tubes that carry air to them.

• The respiratory system brings in oxygen and removes carbon dioxide from the body, and helps regulate pH.

• The urinary system, made up of kidneys, urinary bladder, and tubes that convey urine, rids the body of nitrogenous wastes, and regulates fluid balance and pH.

• The bones skeletal system protect the body and aid in movement; they also store minerals and calcium and produce blood cells in bone marrow.

• The muscular system, made up of the skeletal muscles, provides movement and generates heat for the body.

• Smooth muscle and cardiac muscle provide movement of internal organs.

• The nervous system, made up of the brain, spinal cord, and nerves, receives and processes information, and causes the body to react to stimuli; the nervous system regulates the activities of the other organ systems of the body.

• The endocrine system consists of hormone-secreting glands, helps to regulate the functioning of other body systems.

• The reproductive systems produce sperm and egg cells, allowing humans to produce more of their own kind.

Integumentary System

• The skin and its accessory organs make up the integumentary system.

• Skin plays a significant role in homeostasis by protecting underlying tissues from trauma, infection, and water loss, and by helping to regulate temperature.

• The skin synthesizes vitamin D and houses sensory receptors.

Regions of the Skin• The skin has two regions:• Outer epidermis made up of stratified squamous

epithelium, with waterproof keratin, and pigment-producing melanocytes

• Inner dermis made up of fibrous connective tissue with collagen and elastic fibers, blood vessels, and sensory receptors.

• A subcutaneous layer, composed of loose connective and adipose tissues, connects the dermis to underlying organs.

Human skin anatomy

Accessory Organs of the Skin

• Nails, glands, and hair are structures of epidermal origin even though they are located in the dermis.

• Nails are a protective covering of the ends of the fingers and toes; these increase dexterity.

• Nails grow from cells in the nail root; these become keratinized as they grow over the nail bed.

Nail anatomy

• Hair follicles are in the dermis and extend through the epidermis; arrector pili muscles allow the hair to become erect.

• Each hair follicle has oil (sebaceous) glands that secrete moisturizing sebum.

• Sweat (sudoriferous) glands are present in all regions of the skin and play a role in temperature regulation.

Homeostasis

• Homeostasis is the relative constancy of the body’s internal environment.

• Internal conditions fluctuate slightly in dynamic equilibrium.

• Illness results if internal conditions vary to a great degree.

• A homeostatic mechanism in the body has a sensor, a regulatory center, and an effector.

Homeostasis

Negative Feedback

• Negative feedback is the primary homeostatic mechanism that keeps a variable close to its set point.

• A home heating system, with its temperature set at 68oF (the set point), operates by negative feedback; many negative feedback mechanisms in the body function in a similar manner.

Negative feedback

Regulation of Body Temperature• The regulatory center for body

temperature is located in the brain’s hypothalamus.

• When body temperature is below normal, the hypothalamus sends nervous impulses to the skin blood vessels and they constrict, conserving heat.

• If cooling continues, skeletal muscles are signaled, shivering ensues, generating heat and raising body temperature.

• When body temperature is higher than normal, the regulatory center directs skin blood vessels to dilate, radiating heat to the outside.

• Sweat glands are also activated, and evaporation helps to lower body temperature.

• Temperature drops to normal, and the regulatory center is inactivated.

Homeostasis and body temperature regulation

Positive Feedback• Positive feedback mechanisms bring

about an ever greater change in the same direction and does not achieve relative stability; they may have a cut-off point.

• Examples of positive feedback:• Childbirth and the hormone oxytocin

• Blood clotting• Digestion of protein in the stomach

• Certain fevers

Homeostasis and Body Systems

• The internal environment of the body consists of blood and tissue fluid.

• The chemical composition of tissue fluid remains constant only as long as blood composition remains constant.

• All systems of the body contribute toward maintaining homeostasis and therefore a relatively constant internal environment.

Regulation of tissue fluid composition

Chapter Summary

• Human tissues are organized into four groups.

• Epithelial tissues cover the body and line its cavities.

• Connective tissues bind body parts together.

• Muscle tissue allows the enter body or its internal organs to move and contract.

• Nervous tissue conducts nerve impulses.

• The internal organs occur within cavities.

• Major body cavities include the ventral cavity, with thoracic and abdominal portions, and the dorsal cavity, which includes the cranial cavity and vertebral canal.

• Body membranes line body cavities and the internal spaces of organs, and include mucous, serous, and synovial membranes, and the meninges.

• Organ systems provide coordinated functions for the body.

• Processing and transporting functions are provided by the digestive, cardiovascular, lymphatic, respiratory, and urinary systems.

• The musculoskeletal system supports the body and permits movement.

• The nervous system detects changes and responds to stimuli and controls the activities of other organ systems.

• The endocrine system produces hormones, some of which affect the reproductive system.

• Skin covers and protects the body, houses sensory receptors, and helps in temperature regulation.

• Homeostasis is the relative constancy of the internal environment.

• Most homeostasic mechanisms are by negative feedback, although some use positive feedback.

• All organ systems contribute to the homeostasis of tissue fluid and blood.

Chapter 12: Digestive System

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Digestive system

The Mouth• Lips and cheeks enclose the mouth.

• Taste buds on the tongue provide the sense of taste; skeletal muscle in the tongue allows it to move.

• The roof of the mouth is formed by the hard and soft palates that separate it from the nasal cavities.

• The soft palate ends in a finger-shaped projection called the uvula.

• Tonsils at the back sides of the mouth protect against infections.

• Tonsillitis results when the tonsils become inflamed; the infection can spread to the middle ears.

• Three pairs of salivary glands send saliva (containing salivary amylase for digestion of starch to maltose) into the mouth.

The Teeth• Twenty deciduous (baby) teeth are

replaced by 32 adult teeth. • Each tooth has a crown and a root. • The crown has a layer of enamel, dentin,

and an inner pulp with nerves and blood vessels that extend into the root.

• The tongue mixes the chewed food with saliva and then forms the mixture into a mass called a bolus in preparation for swallowing.

Adult mouth

Longitudinal section of a tooth

The Pharynx• The air passage and food passage cross

in the pharynx because the trachea is ventral to the esophagus.

• Swallowing occurs in the pharynx and is a reflex action.

• During swallowing, the air passage is usually blocked off by the soft palate and uvula, and the trachea moves under the epiglottis to cover the glottis opening to the windpipe.

Swallowing

The Esophagus• The esophagus is a muscular tube that

conducts food through the thoracic cavity and diaphragm into the stomach.

• Peristalsis begins in the esophagus; this collapsed tube moves the bolus of food downward after swallowing occurs.

• Heartburn is a burning pain when acidic stomach contents enter the esophagus.

• No chemical digestion occurs in the esophagus.

• The entrance of the esophagus to the stomach is marked by a constriction, called a sphincter; the sphincter must relax in order for food to enter the stomach.

• The sphincter prevents food from backing up into the esophagus.

The Wall of the Digestive Tract• The digestive tract wall has four layers:

• Mucosa (mucous membrane – secretes digestive enzymes and mucus),

• Submucosa (loose connective tissue – houses blood and lymph vessels),

• Muscularis (two layers of smooth muscle - for peristalsis), and

• Serosa (serous membrane – secretes serous fluid to prevent sticking).

Wall of the digestive tract

The Stomach• The stomach expands to store food.• Food in the stomach is churned, mixing

the food with gastric juices containing hydrochloric acid and pepsin for the digestion of protein to peptides.

• Alcohol, but not food, is absorbed here.• In 2–6 hours, the soupy chyme leaves the

stomach. • Ulcers are usually caused by a bacterial

infection.

Anatomy and histology of the stomach

Ulcer

The Small Intestine• The small intestine, averaging about 6

meters in length, is small in diameter.• The first 25 cm is the duodenum that

receives bile from the gallbladder and pancreatic juice containing pancreatic lipase and trypsin for digestion of protein to peptides, as well as lipase for digestion of fat to glycerol and fatty acids.

• Pancreatic juice contains NaHCO3 that is basic and neutralizes the acidic chyme.

• Enzymes that finish the process of digestion are produced by the intestinal wall.

• Walls of the small intestine have finger-like projections called villi where nutrient molecules are absorbed into the cardiovascular and lymphatic systems.

• Villi have microvilli that increase the surface area available for absorption.

• The small lymphatic capillary in a villus is called a lacteal.

Anatomy of the small intestine

Regulation of Gastric Secretions

• Both the nervous system and chemicals called hormones regulate digestive juice secretion.

• In response to eating protein foods, the hormone gastrin is produced by the lower part of the stomach and flows through the bloodstream to stimulate the stomach to produce digestive juice.

• The duodenal wall produces gastric inhibitory peptide (GIP) to inhibit gastric gland secretion.

• The hormones secretin and cholecystokinin (CCK) are produced by the duodenal wall and stimulate the pancreas to secrete digestive juice and the gallbladder to release bile.

• Acidic chyme stimulates the secretion of secretin, while fatty chyme with protein triggers CCK release.

Hormonal control of digestive gland secretions

The Large Intestine• The large intestine consists of the cecum,

colon, rectum and anal canal.

• The large intestine does not produce digestive enzymes but does absorb water, salts, and some vitamins.

• The colon includes the ascending colon, the transverse colon, the descending colon, and the sigmoid colon.

• The appendix is an extension of the cecum.

• Indigestible material is stored in the rectum until the anus allows defecation.

• Anaerobic bacteria in the feces break down indigestible material and produce some vitamins.

• Water tests that show the presence of the bacterium Escherichia coli indicate water is contaminated.

Junction of the small intestine and the large intestine

• Polyps are small growths arising from the epithelial lining that may be benign or cancerous.

• Diarrhea and constipation are two common complaints of the large intestine.

• Causes of diarrhea include infection of the lower tract and nervous stimulation, both moving feces more rapidly than normal, but also causing dehydration if prolonged.

• Water and fiber in the diet can prevent constipation where the feces become too dry and hard.

• Hemorrhoids are enlarged and inflamed blood vessels at the anus; this condition is associated with chronic constipation.

• Regular elimination reduces the time the colon wall is exposed to cancer-promoting agents in the feces and may help prevent cancer.

Defecation reflex

The Pancreas

• The pancreas produces pancreatic juice, which contains digestive enzymes for carbohydrate (pancreatic amylase), protein (trypsin), and fat (lipase), along with sodium bicarbonate (NaHCO3) to neutralize acid in chyme.

• The pancreas is also an endocrine gland that secretes insulin and glucagon, hormones that keep blood glucose within normal limits.

The Liver• The liver produces bile, which is stored in

the gallbladder. • Bile emulsifies fats; it is a yellowish-green

substance containing bilirubin from hemoglobin breakdown and bile salts derived from cholesterol.

• The liver acts as gatekeeper to the blood and receives blood from the small intestine by way of the hepatic portal vein.

Hepatic lobules

• The functions of the liver are many:• detoxifies blood,

• stores iron and vitamins, • makes plasma proteins,

• stores glucose as glycogen, • produces urea from amino acids,

• removes bilirubin after dismantling blood cells, and

• regulates blood cholesterol level when producing bile salts.

Hepatic portal system

Liver Disorders• When a person has a liver disorder,

jaundice may occur.• Jaundice is a yellowish tint to eyes and

skin, indicating abnormal levels of blood bilirubin.

• Hepatitis is inflammation of the liver; different strains of virus cause hepatitis A, B, etc.

• Cirrhosis is scar tissue that can form when the liver is diseased or killed by exposure to alcohol.

The Gallbladder• The gallbladder is a pear-shaped muscular

organ that stores bile until it is sent to the duodenum.

• Water is reabsorbed in the gallbladder making the bile thick and mucus-like.

• Bile enters the duodenum via the common bile duct.

• Gallstones are crystals of cholesterol.

• Peptidases and maltase, produced by the small intestine, complete the digestion of proteins and starches, respectively.

• Glucose and amino acids are absorbed into the blood capillaries of the villi.

• Fatty acids and glycerol rejoin in the villi to produce lipoprotein droplets which enter the lacteals.

• Digestive enzymes speed specific reactions and function best at a warm body temperature and optimum pH.

Conditions for Digestion

• For digestion to occur the correct enzyme, optimum pH, optimum temperature, and the correct substrate must be present.

• Exact conditions can be determined during laboratory experiments.

• Most digestive enzymes, aside from pepsin, require a basic pH.

Digestion experiment

Food guide pyramid: A guide to daily food choice

Carbohydrates• Complex carbohydrates from foods like

breads and pasta can be converted to glucose and used rapidly.

• Body cells can utilize fatty acids as an energy source, but brain cells require glucose, thus carbohydrates are an essential part of the diet.

• Complex, rather than simple, carbohydrates should make up the bulk of the diet.

• Simple carbohydrates like table sugar (sucrose) contribute to energy needs and weight gain without supplying other nutrients.

• Insoluble fiber helps regularity and may help prevent cancer by limiting the time substances are in contact with the intestinal wall.

• Soluble fiber combines with bile acids and cholesterol in the intestine and prevents them from being absorbed.

Complex carbohydrates

Proteins• Meat, milk or eggs are complete proteins;

they provide all 20 essential amino acids. • Because individual vegetables do not

provide all essential amino acids, vegetarians must be careful to consume a combination of legumes, grains, vegetables, seeds and nuts to secure complementary proteins.

• The amino acid pool relies on continual uptake; amino acids are not stored.

Ancient versus modern diet of native Hawaiians

Lipids• Fat and cholesterol are lipids.

• Lipids, found in fats and oils, should be used sparingly.

• Current guidelines suggest that fat should account for 30% or less of daily calories.

• High-density lipoproteins (HDL) carry cholesterol to the liver and is considered to be “good”.

• Low density lipoprotein (LDL) takes cholesterol to the cells and may contribute to the development of plaque on blood vessels walls; it is considered to be “bad”.

• Saturated fatty acids lack double bonds and raise LDL cholesterol levels.

• Linoleic acid and linolenic acid are two essential fatty acids the body cannot make; polyunsaturated fats supply these.

Fake Fat• Olestra looks, tastes, and acts like real fat

but the digestive system cannot digest it; therefore, it is called “fake fat”.

• However, fat-soluble vitamins are taken up by olestra and pass through the digestive system unabsorbed.

• Those who consume olestra have reduced carotenoids in their blood.

Vitamins• Vitamins are organic compounds that the

body cannot produce but needs for metabolic purposes; some are portions of coenzymes.

• Vitamins A, E, and C are antioxidants that protect cell contents from damage due to free radicals.

• Free radicals donate an electron to DNA, proteins, enzymes, membranes, etc. and can damage cell structures or cause cancer.

• Vitamin D• A precursor molecule in skin is converted

to vitamin D after exposure to ultraviolet (UV) light.

• Vitamin D is modified first in the kidneys and then the liver until it becomes calcitriol, which is needed for calcium absorption in intestines.

• In the U.S., milk is often fortified by vitamin D.

• Vitamin D is a fat-soluble vitamin.

Illnesses due to vitamin deficiency

Minerals• The body contains more than 5 grams of

each major minerals and less than 5 grams of each trace minerals.

• Calcium and phosphorus are in bones and teeth.

• Potassium and sodium are involved in nerve conduction.

• Trace minerals are critical in various enzymes and hormones.

Minerals in the body

• Calcium• Calcium is needed to have strong bones. • Older women in particular are at risk for

osteoporosis, a degenerative bone disease due to insufficient intake of calcium because bone cells are constantly building and eroding bone tissue.

• Calcium supplement with vitamin D (and also estrogen for women) can help prevent this bone loss.

• Sodium• Most Americans have too much salt in

their diet. • High sodium intake is linked to

hypertension in some persons.• About one-third of the sodium we

consume occurs naturally in foods; another one-third is added during commercial processing; and the final one-third is added during cooking or at the table in the form of table salt.

Eating Disorders• Obesity is defined as a body weight of

more than 20% above the ideal weight for that person.

• Obesity can have hormonal, metabolic, and social causes.

• For many, a commitment to a sensible diet and exercise program can prevent obesity or a harmful cycle of weight gain-and-loss.

Recognizing obesity

• Bulimia nervosa is characterized by a restrictive diet, binging, and purging.

• Psychotherapy and antidepressants may help.

• Anorexia nervosa is characterized by a distorted body image and feeling fat even when emaciated.

• It can be life-threatening and carries the same risks as starvation.

Recognizing bulimia nervosa

Recognizing anorexia nervosa

• The mouth, pharynx, esophagus, stomach, small and large intestines have distinct functions and hormones control digestive gland secretions.

• The pancreas, liver, and gallbladder are accessory organs of digestion; their secretions assist digestion.

• The products of digestion are small molecules, such as amino acids and glucose, that can cross plasma membranes.

• Digestive enzymes are specific and have an optimum temperature and pH.

• Proper nutrition supplies the body with energy and nutrients, including essential amino acids and fatty acids, and all vitamins and minerals.

• Anorexia nervosa, bulimia, and obesity are primary eating disorders in the United States.

Lab Ex 19: Platyhelminthes (flatworms)

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Flatworms• Flatworms are characterized by the tissue

level of organization and a sac body plan.

• These acoelomates (NO coelom) have three germ layers, and have all organs except respiratory and circulatory organs.

• The flat body facilitates diffusion of oxygen and other molecules from cell to cell.

• Planarians• Planarians are freshwater, free living,

flatworms. • Flame cells function in excretion. • The small brain extends to a ladder

arrangement of nerves. • Light-sensitive organs (eyespots) are in

the head; planarians exhibit cephalization. • One organism has both male and female

sex organs – they are hermaphroditic.

Planarian

• Parasitic Flatworms• Flukes and tapeworms are two classes of

parasitic flatworms; both have intermediate hosts.

• Flukes are oval to elongate and have suckers at the anterior end.

• Blood flukes cause schistosomiasis; other flukes infect the digestive tract, bile duct, and lungs.

• A tapeworm has an anterior scolex with hooks and suckers to hold itself inside the gut.

Schistosomiasis

Lab Ex 20: Aschelminthes(roundworms)

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Roundworms• Roundworms have the tube-within-a-tube

plan; they are prevalent in soil and some parasitize animals and plants.

• The pseudocoelom is a body cavity incompletely lined with mesoderm.

• The fluid-filled interior forms a hydrostatic skeleton.

• Most species of roundworms have separate males and females.

Coelom structure and function

• Ascaris• Ascaris larvae are swallowed and burrow

through the intestinal wall and make their way through various organs until they reach the lungs.

• In the lungs, they grow in size for 10 days, then move up to the throat, and are then swallowed.

• After they mature in the intestine, females produce eggs that pass out with feces.

Roundworm anatomy

• Other Roundworms• Trichinosis is a roundworm infection from

eating undercooked pork containing encysted Trichinella larvae.

• The filarial worm is carried by mosquitoes and causes elephantiasis by blocking lymphatic drainage.

• Pinworms are common infections in children.

• Hookworm is a more serious infection seen in the southern United States.