Anatomy and Physiology

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Unit 1
Chapter 8: Introduction to Tissues.
Chapter 9: Tissue Types

INTRODUCTION

  • Tissue: Group of similar cells that perform a common function.
  • Matrix: Nonliving intercellular material.

PRINCIPAL TYPES OF TISSUE

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue

EXTRACELLULAR MATRIX

  • Extracellular matrix (ECM) is a complex, nonliving material between cells in a tissue
  • Some tissues have a large amount of ECM; other tissues have hardly any.
  • Different kinds of components give ECM in different tissues a variety of characteristics.

EXTRACELLULAR MATRIX (cont.)

  • Components
  • Water
  • Proteins
  • Structural proteins
  • Collagen: strong, flexible protein fiber.
  • Elastin: elastic fibers.
  • Includes glycoproteins: proteins with a few carbohydrate attachments.
  • Fibronectin and laminin help connect the ECM components to cells by binding with integrins in plasma membranes
  • Glycoprotein attachments also allow local communication within a tissue

EXTRACELLULAR MATRIX (cont.)

  • Proteoglycans
  • Hybrid molecules that are mostly carbohydrates attached to a protein backbone.
  • Examples: chondroitin sulfate, heparin, and hyaluronate.
  • Different proteoglycans give different characteristics to ECM, such as thickness and shock absorption .

EXTRACELLULAR MATRIX (cont.)

  • Functions
  • Helps bind tissues together structurally
  • ECM components bind to each other and to integrins in plasma membranes of cells
  • Some tissues are held together primarily by intercellular junctions
  • Allows local communication among ECM and various cells through connection with integrins in plasma membranes

EPITHELIAL TISSUE

  • Types and locations
  • Epithelium is divided into two types:
  • Membranous (covering or lining) epithelium
  • Glandular epithelium
  • Locations
  • Membranous epithelium: covers the body and some of its parts and lines the serous cavities; blood and lymphatic vessels; and respiratory, digestive, and genitourinary tracts
  • Glandular epithelium: secretory units of endocrine and exocrine glands.

EPITHELIAL TISSUE (cont.)

  • Functions
  • Protection
  • Sensory functions
  • Secretion
  • Absorption
  • Excretion

EPITHELIAL TISSUE (cont.)

  • Generalizations about epithelial tissue
  • Limited amount of matrix material.
  • Membranous type attached to a basement membrane.
  • Avascular.
  • Cells are in close proximity, with many desmosomes and tight junctions.
  • Capable of reproduction.

EPITHELIAL TISSUE: MEMBRANOUS

  • Classification of epithelial tissue
  • Membranous (covering or lining) epithelium .
  • Classification based on cell shape
  • Squamous
  • Cuboidal
  • Columnar
  • Pseudostratified columnar

EPITHELIAL TISSUE:
MEMBRANOUS (cont.)

  • Classifications based on layers of cells
  • Simple epithelium

Simple squamous epithelium

One-cell layer of flat cells

Permeable to many substances.

Examples: endothelium, which lines blood vessels; mesothelium, which lines pleura

Simple cuboidal epithelium

One-cell layer of cuboidal cells

Found in many glands and ducts

EPITHELIAL TISSUE (cont.)

Classifications based on layers of cells (cont.)

Simple columnar epithelium.

Single layer of tall, column-shaped cells

Cells often modified for certain functions such as goblet cells (secretion), cilia (movement), microvilli (absorption)

Often lines hollow visceral structures

Pseudostratified columnar epithelium

Columnar cells of differing heights

All cells rest on basement membrane but may not reach the free surface above

Cell nuclei at odd and irregular levels

Found lining air passages and segments of male reproductive system

Motile cilia and mucus are important modifications

EPITHELIAL TISSUE (cont.)

  • Classifications based on layers of cells (cont.)
  • Stratified epithelium

Keratinized stratified squamous epithelium

Multiple layers of flat, squamous cells

Cells filled with keratin

Covering outer skin on body surface

Nonkeratinized stratified squamous epithelium

Lining vagina, mouth, and esophagus

Free surface is moist

Primary function is protection

Stratified cuboidal epithelium

Two or more rows of cells are typical

Basement membrane is indistinct

Located in sweat gland ducts and pharynx

EPITHELIAL TISSUE (cont.)

  • Classifications based on layers of cells (cont.)

Stratified columnar epithelium

Multiple layers of columnar cells

Only most superficial cells are typical in shape

Rare

Located in segments of male urethra and near anus

Transitional epithelium

Located in lining of hollow viscera subjected to stress (e.g., urinary bladder)

Often 10 or more layers thick

Protects organ walls from tearing

EPITHELIAL TISSUE: GLANDULAR EPITHELIUM

  • Glandular epithelium
  • Specialized for secretory activity
  • Exocrine glands: discharge secretions into ducts.
  • Endocrine glands: “ductless” glands; discharge secretions directly into blood or interstitial fluid.

CONNECTIVE TISSUE

  • Functions, characteristics, and types
  • General function: connects, supports, transports, and protects.
  • General characteristics
  • ECM predominates in most connective tissues and determines its physical characteristics.
  • Consists of fluid, gel, or solid matrix, with or without extracellular fibers (collagenous, reticular, and elastic) and proteoglycans or other compounds that thicken and hold together the tissue .

CONNECTIVE TISSUE (cont.)

  • Four main types (Table 5-6)
  • Fibrous
  • Loose (areolar)
  • Adipose
  • Reticular
  • Dense
  • Irregular
  • Regular (collagenous and elastic)
  • Bone
  • Compact bone
  • Cancellous bone
  • Cartilage
  • Hyaline
  • Fibrocartilage
  • Elastic
  • Blood

CONNECTIVE TISSUE: FIBROUS CONNECTION TISSUE

  • Fibrous connective tissue
  • Loose (areolar) connective tissue
  • One of the most widely distributed of all tissues
  • Intercellular substance is prominent and consists of collagenous and elastic fibers loosely interwoven and embedded in soft viscous ground substance.
  • Several kinds of cells present, notably fibroblasts and macrophages, also mast cells, plasma cells, fat cells, and some white blood cells
  • Function: stretchy, flexible connection.

CONNECTIVE TISSUE: FIBROUS CONNECTION TISSUE (cont.)

  • Adipose tissue
  • Similar to loose connective tissue but contains mainly fat cells
  • Functions: protection, insulation, support, and food reserve.
  • Reticular tissue
  • Forms framework of spleen, lymph nodes, and bone marrow
  • Consists of network of branching reticular fibers with reticular cells overlying them.
  • Functions: defense against microorganisms and other injurious substances; reticular meshwork filters out injurious particles and reticular cells phagocytize them

CONNECTIVE TISSUE:
BONE TISSUE

  • Bone tissue
  • Uniquely hard and strong connective tissue type.
  • Cells (osteocytes) embedded in a calcified matrix.
  • Inorganic component of matrix accounts for 65% of total bone tissue.
  • Functions
  • Support
  • Protection
  • Point of attachment for muscles
  • Reservoir for minerals
  • Supports blood-forming tissue

CONNECTIVE TISSUE:
BONE TISSUE (cont.)

  • Compact bone .
  • Osteon (Haversian system)
  • Structural unity of bone
  • Spaces for osteocytes called lacunae
  • Matrix present in concentric rings called lamellae
  • Canaliculi are canals that join lacunae with the central Haversian canal.
  • Cell types
  • Osteocyte: mature, inactive bone cell.
  • Osteoblast: active bone-forming cell.
  • Osteoclast: bone-destroying cell.

CONNECTIVE TISSUE: CARTILAGE

  • Cartilage
  • Chondrocyte is the only cell type present.
  • Lacunae house cells as in bone.
  • Avascular: nutrition of cells depends on diffusion of nutrients through matrix.
  • Heals slowly after injury because of slow nutrient transfer to cells.
  • Perichondrium is membrane that surrounds cartilage.

CONNECTIVE TISSUE: CARTILAGE (cont.)

  • Types
  • Hyaline.
  • Appearance is shiny and translucent.
  • Most prevalent type of cartilage.
  • Located on ends of articulating bones.
  • Fibrocartilage.
  • Strongest and most durable type of cartilage
  • Matrix is semirigid and filled with strong white fibers.
  • Found in intervertebral disks and pubic symphysis.
  • Serves as shock-absorbing material between bones at the knee (menisci)
  • Elastic .
  • Contains many fine elastic fibers.
  • Provides strength and flexibility.
  • Located in external ear and larynx.

CONNECTIVE TISSUE: BLOOD

  • Blood
  • A liquid tissue .
  • Contains neither ground substance nor fibers
  • Composition of whole blood
  • Liquid fraction (plasma) is the matrix; 55% of total blood volume
  • Formed elements contribute 45% of total blood volume
  • Red blood cells (erythrocytes)
  • White blood cells (leukocytes)
  • Platelets (thrombocytes)

CONNECTIVE TISSUE:
BLOOD (cont.)

  • Functions
  • Transportation
  • Regulation of body temperature
  • Regulation of body pH
  • White blood cells destroy bacteria
  • Circulating blood tissue is formed in the red bone marrow by a process called hematopoiesis; the blood-forming tissue is sometimes called hematopoietic tissue

MUSCLE TISSUE

  • Types.
  • Skeletal, or striated voluntary
  • Smooth, also known as nonstriated involuntary or visceral
  • Cardiac, or striated involuntary
  • Microscopic characteristics
  • Skeletal muscle: threadlike cells with many cross-striations and many nuclei per cell
  • Smooth muscle: elongated narrow cells, no cross-striations, one nucleus per cell
  • Cardiac muscle: branching cells with intercalated disks (formed by abutment of plasma membranes of two cells)

NERVOUS TISSUE

  • Functions: rapid regulation and integration of body activities
  • Special characteristics
  • Excitability
  • Conductivity
  • Organs
  • Brain
  • Spinal cord
  • Nerves

NERVOUS TISSUE (cont.)

  • Cell types.
  • Neuron: conducting unit of system .
  • Cell body, or soma
  • Processes
  • Axon (single process): transmits nerve impulse away from the cell body
  • Dendrite (one or more): transmits nerve impulse toward the cell body and axon
  • Neuroglia: special connecting, supporting, coordinating cells that surround neurons

BODY MEMBRANES

  • Thin tissue layers that cover surfaces, line cavities, and divide spaces or organs (Figure 5-38; Table 5-8)
  • Epithelial membranes are most common type (Figure 5-39)
  • Cutaneous membrane (skin)
  • Primary organ of integumentary system.
  • One of the most important organs.
  • Approximately 16% of body weight.

BODY MEMBRANES:
EPITHELIAL MEMBRANES (cont.)

  • Serous membrane (serosa)
  • Parietal membranes: line closed body cavities.
  • Visceral membranes: cover visceral organs.
  • Pleura: surrounds a lung and lines the thoracic cavity
  • Peritoneum: covers the abdominal viscera and lines the abdominal cavity

BODY MEMBRANES:
EPITHELIAL MEMBRANES (cont.)

  • Mucous membrane (mucosa)
  • Lines and protects organs that open outside the body.
  • Found lining ducts and passageways of the respiratory, digestive, and other tracts.
  • Lamina propia: fibrous connective tissue underlying mucous epithelium.
  • Mucus is made of mostly of water and mucins—proteoglycans that form a double-layer protection against environmental microbes (Figure 5-40)

BODY MEMBRANES (cont.)

  • Connective tissue membranes
  • Do not contain epithelial components.
  • Synovial membranes line the spaces between bone in joints.
  • Have smooth and slick membranes that secrete synovial fluid.
  • Help reduce friction between opposing surfaces in a movable joint.
  • Synovial membranes also line bursae.

THE BIG PICTURE: TISSUES, MEMBRANES, AND THE WHOLE BODY

  • Tissues and membranes maintain homeostasis
  • Epithelial tissues
  • Form membranes that contain and protect the internal fluid environment
  • Absorb nutrients
  • Secrete products that regulate functions involved in homeostasis
  • Connective tissues
  • Hold organs and systems together
  • Form structures that support the body and permit movement

THE BIG PICTURE: TISSUES, MEMBRANES, AND THE WHOLE BODY (cont.)

  • Muscle tissues
  • Work with connective tissues to permit movement.
  • Nervous tissues
  • Work with glandular epithelial tissue to regulate body function.