Body Tissues And Membranes

Body Tissues and Membranes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Body Tissues o

Composed of specialized cells of similar structure and perform a common function Four major types

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Epithelial Connective Muscular Nervous

Organs are typically composed of all 4 types of tissue

Epithelial Tissue o o o o o o

Cells are tightly packed Protects external and internal body surfaces Also secretes and absorbs substances Epithelial cells can divide to replace lost or damaged cells Cells are avascular (lack a blood supply) Has a free surface and a basement membrane

Epithelial Tissue o

Classification of epithelial tissue •

Number of cell layers 

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•

Simple epithelial tissue is one cell layer thick Stratified epithelial tissue is composed of two or more layers

Shape of the cells   

Squamous epithelium has flattened cells Cuboidal epithelium has cube-shaped cells Columnar epithelium has elongated cells

Epithelial Tissue • Squamous Epithelium 

Simple squamous epithelium  

Composed of a single layer of flattened cells Found in areas where simple diffusion occurs

Epithelial Tissue 

Stratified squamous epithelium  





Has many cell layers Shape of deeper cells may be cuboidal or columnar Shape of outer cells are flattened and squamous-shaped Found in the outer portion of the skin and in body orifices

Epithelial Tissue •

Cuboidal Epithelium Simple cuboidal epithelium

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   

Single layer of cube-shaped cells attached to a basement membrane Found in glands where its function is secretion Covers the ovaries Lines most of the kidney tubules where it absorbs and secretes substances

Stratified cuboidal epithelium

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 

Often only has two layers Mostly found lining the larger ducts of certain glands

Fig 4.3

Epithelial Tissue •

Columnar Epithelium Simple columnar epithelium

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Cells are longer than they are wide Modified to perform particular functions Lines digestive organs and the uterine tubes

Stratified columnar epithelium

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 

Not very common Located in parts of the pharynx and in the male urethra

Fig 4.4

Epithelial Tissue •

Pseudostratified Columnar Epithelium 

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Appears to have more than one layer of cells, but only has one true layer Each cell touches the basement membrane Pseudostratified ciliated columnar epithelium lines parts of the reproductive system and air passageways of the respiratory system

Fig 4.5

Epithelial Tissue •

Transitional Epithelium  

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Changes in response to tension Located in urinary bladder, the ureters, and part of the urethra Allows these organs to stretch

II Connective Tissue o

Varying degree of (mostly good) vascularity can divide Cells are farther apart than ET Cells are separated by an extracellular matrix that is composed of an organic ground substance that contains the following fibers:

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Collagen fibers Elastic fibers Reticular fibers

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Ground substance binds, supports and provide a medium through which substance may be transferred between the blood and the cells within the tissue. Binds structures together, provides support and protection, produces blood cells, and stores fat Bone, cartilage (rigid); loose CT and dense (flexible)

Connective Tissue o

Fibrous Connective Tissue (Connective Tissue Proper) •

Loose (areolar) connective tissue   

Cells of this tissue are mainly fibroblasts Contains many collagen and elastin fibers Adipose tissue is a type of loose connective tissue in which the cells enlarge and store fat

Connective Tissue •

Dense connective tissue  

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Has thick bundles of collagen fibers In dense regular connective tissue the bundles are parallel (as in tendons and ligaments) In dense irregular connective tissue the bundles run in different directions (in the dermis) In reticular connective tissue the cells are called reticular cells and the matrix contains only reticular fibers (also called lymphatic tissue)

Fig 4.9

Connective Tissue o

•

Cartilage

Cells called chondrocytes are found in small chambers called lacunae Because it is avascular, it heals slowly Hyaline cartilage

• •   

•

Most common type Contains only collagen fibers Found in the nose, ends of long bones and ribs, and in the supporting rings of the trachea

Elastic cartilage 

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•

Matrix contains many elastic fibers; also contains collagen fibers; more flexible than hyaline cartilage Found in the outer ear

Fibrocartilage   

Matrix contains strong collagen fibers Absorbs shock and reduces friction between joints Found between the vertebrae and in the knee joint

Fig 4.10

Connective Tissue o

Bone •

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Extremely hard matrix composed of mineral salts deposited around collagen fibers Osteocytes (bone cells) Compact bone Spongy bone

Fig 4.11

Connective Tissue o

Blood •

Composed of formed elements (cells) 

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

•

Red blood cells (erythrocytes) - carry oxygen White blood cells (leukocytes) – fight infection Platelets (thrombocytes) – blood clotting

Matrix is called plasma and is not formed by the tissue cells

Fig 4.12

Muscular Tissue o

Skeletal Muscle (voluntary muscle) • • • • •

Attached to bones of the skeleton Causes movement of body parts Have a cylindrical shape and are long Muscle fibers (cells) have multiple, peripherally located nuclei Muscle fibers appear striated due to the placement of actin and myosin filaments in the fiber

Fig 4.13

Muscular Tissue o

Smooth Muscle (visceral muscle) • • •

Spindle-shaped cells Not under voluntary control (involuntary) Found in the walls of hollow viscera (organs)

Fig 4.14

Muscular Tissue o

Cardiac Muscle • • • • • •

Found only in the walls of the heart Pumps blood Cardiac muscle cells have striations, like skeletal muscle Is involuntary, like smooth muscle Cardiac muscle cells have a single, centrally located nucleus Cardiac muscle cells are bound to one another by intercalated disks

Fig 4.15

Nervous Tissue o o

Found in the brain and spinal cord Neurons (nervous tissue cells) conduct impulses A neuron has three parts:

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Dendrite – receives an impulse Cell body – contains the nucleus Axon – conducts nerve impulses

Neuroglia (more numerous nervous tissue cells)

Fig 4.16

Nervous Tissue o

Neuroglia (more numerous nervous tissue cells) Support and nourish neurons Types of neuroglia found in the brain:

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Microglia Astrocytes Oligodendrocytes Ependymal cells

Schwann cells are neuroglia located outside the brain or spinal cord

Extracellular Junctions o

Junctions between cells help cells function as a tissue Types of cell junctions:

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Tight junction – plasma membrane proteins join, forming an impermeable barrier Gap junction – plasma membrane channels join, allowing substances to pass between the two cells Adhesion junction (desmosome) – adjacent plasma membranes held together by extracellular filaments

Fig 4.17

Glands o o o

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Consists of one or more cells that produce and secrete a product Most are composed primarily of epithelium Exocrine glands – secrete their product onto the outer surface or into a cavity Endocrine glands are ductless and secrete their product internally to be transported by the bloodstream

Membranes o

Mucous membranes •

• •

Line interior walls of the organs and tubes that open to the outside of the body Consist of epithelium overlying a layer of loose connective tissue Epithelium contains goblet cells that secrete mucus

Membranes o

Serous membranes •

Parietal membranes line the thoracic and abdominopelvic cavities Visceral membranes cover internal organs Consist of a layer of simple squamous epithelium overlying a layer of loose connective tissue Secrete serous fluid that lubricates the membranes Pleura – serous membranes in the thorax

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• •

Parietal pleura – lines thoracic wall Visceral pleura – covers the surface of the lungs

Pericardium – covers the heart Peritoneum – serous membranes within the abdomen  

Parietal peritoneum – lines the abdominopelvic wall Visceral peritoneum – covers the organs in the abdominopelvic cavity

Membranes o

Synovial membranes • • •

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Line freely movable joint cavities Composed of connective tissue Secrete synovial fluid that lubricates the ends of bones

Meninges • • •

Found within the posterior cavity Composed entirely of connective tissue Protective covering for the brain and spinal cord

Membranes o

Cutaneous membrane (skin) • •

Forms the outer covering of the body Consists of an outer portion of keratinized stratified squamous epithelium attached to a thick layer of dense connective tissue