11-1 Chapter 11: Human Organization. 11-2 Types of Tissues A tissue is composed of specialized cells that perform a function in the body. The human body.

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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

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

Carcinomas – cancers of epithelial tissueSarcomas – cancers of connective tissueLeukemias – cancers of bloodLymphomas – cancers of lymphatic

tissueCancers are more likely to arise in

tissues in which cells divide rapidly.

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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.

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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.

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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.

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Simple squamous epithelium

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Simple cuboidal epithelium

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Simple columnar epithelium

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Pseudostratified ciliated columnar epithelium

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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.

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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.

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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.

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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.

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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.

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Loose fibrous connective tissue

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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.

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Adipose tissue

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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.

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Hyaline cartilage

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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.

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BoneBone 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.

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Compact bone

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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.

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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 cellsDistributes heat

Keeps pH and ions in balanceProtects against blood loss and disease

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Blood, a fluid tissue

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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

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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

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Formed elements of blood

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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.

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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.

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Skeletal muscle

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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.

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Smooth muscle

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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.

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Cardiac muscle

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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 nucleusAxon – carries impulse away from cell

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

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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 debrisAstrocytes provide nutrients and secrete

a hormone called glia-derived growth factor

Oligodendrocytes form myelin.

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A neuron and some types of neuroglia

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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.

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Mammalian body cavities

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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.

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Body MembranesHere 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.

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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.

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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.

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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.

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Organ SystemsOrgans 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.

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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.

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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.

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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.

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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.

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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.

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Regions of the SkinThe 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.

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Human skin anatomy

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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.

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Nail anatomy

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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.

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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.

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Homeostasis

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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.

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Negative feedback

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Regulation of Body TemperatureThe 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.

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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.

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Homeostasis and body temperature regulation

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Positive FeedbackPositive 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 clottingDigestion of protein in the stomach

Certain fevers

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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.

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Regulation of tissue fluid composition

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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.

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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.

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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.

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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.