4- Tissues

TISSUES
Dr. Joher B. Mendez, Jr., RN

Introduction
• Similar cells with a common function are
called tissues.
• The study of tissues is called histology.
• There are four (4) primary or major tissue types:
1. Epithelial Tissue
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue
3

Intercellular Junctions
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Tight junctions
• Close space between cells
• Located among cells that
form linings
Desmosomes
• Form “spot welds” between cells
• Located among outer skin cells
Gap junctions
• Tubular channels between cells
• Located in cardiac muscle cells
Cell membrane
Tight junction
Cell membrane
Desmosome
Cell membrane
Gap junction
4

Extracellular Matrix (ECM)
n Functions
n Helps bind tissues together structurally
n ECM components bind to each other and to
integrins in plasma membranes of cells
n In some tissues, it is primarily intercellular
junctions that hold cells together
n Allows local communication among ECM and
various cells—through connection via
integrins in plasma membranes

Extracellular Matrix (ECM)
n Components
n Water
n Proteins
n Structural proteins
n Collagen—strong, flexible protein fiber; Types
n Elastin—elastic fibers
n Includes glycoproteins—proteins with a few
carbohydrate attachments
n Fibronectin and laminins help connect the ECM
components to cells by binding with integrins in plasma
membranes
n Glycoprotein attachments also allow local communication
within a tissue

Embryonic Development of
Tissues
n Primary germ layers
n
n
n Endoderm
n Mesoderm
n Ectoderm
Gastrulation—process of cell movement and
differentiation, which results in development of
primary germ layers
Histogenesis—the process by which the primary
germ layers differentiate into different kinds of tissue

Types of tissues
n There are 4 main types of tissues:
1) Epithelial tissue
2) Connective tissue
3) Muscle tissue
4) Nervous tissue

Epithelial Tissue
n Functions
n Protection
n Sensory functions
n Secretion
n Absorption
n Excretion

Characteristics of
Epithelial Tissue

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

Simple epithelium
n SIMPLE SQUAMOUS EPITHELIUM
n One-cell layer of flat cells
n Permeable to many substances
n Examples: endothelium—lines blood vessels;
mesothelium—pleura

Simple epithelium
n SIMPLE CUBOIDAL EPITHELIUM
n One-cell layer of cuboidal cells
n Found in many glands and ducts

Simple epithelium
n SIMPLE COLUMNAR EPITHELIUM
n Single layer of tall, column-shaped cells
n Cells often modified for specialized functions—e.g.,
goblet cells (secretion), cilia (movement), microvilli
(absorption)
n Often lines hollow visceral structures

Simple epithelium
n PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
n Columnar cells of differing heights
n All cells rest on basement membrane but may not reach
the free surface above
n Cell nuclei at odd and irregular levels
n Found lining air passages and segments of male
reproductive system
n Motile cilia and mucus are important modifications

Stratified epithelium
n STRATIFIED SQUAMOUS (KERATINIZED) EPITHELIUM
n Multiple layers of flat, squamous cells
n Cells filled with keratin
n Covers outer skin on body surface

Stratified epithelium
n STRATIFIED SQUAMOUS (NONKERATINIZED)
EPITHELIUM
n Lines vagina, mouth, and esophagus
n Free surface is moist
n Primary function is protection

Stratified epithelium
n Stratified cuboidal epithelium
n Two or more rows of cells are typical
n Basement membrane is indistinct
n Located in sweat gland ducts and pharynx

Stratified epithelium
n STRATIFIED COLUMNAR EPITHELIUM
n Multiple layers of columnar cells
n Only most superficial cells are typical in shape
n Rare
n Located in segments of male urethra and near anus

Stratified epithelium
n STRATIFIED TRANSITIONAL EPITHELIUM
n Located in lining of hollow viscera subjected to stress
(e.g., urinary bladder)
n Often 10 or more layers thick
n Protects organ walls from tearing

Connective Tissue
n Functions, characteristics, and types
n General function—connects, supports,
transports, and protects
n General characteristics—extracellular matrix (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

Glandular Epithelium
• Composed of cells that are specialized to produce and
secrete substances
• There are two (2) types:
• Endocrine glands are ductless (key word: hormone)
• Exocrine glands have ducts
• Unicellular exocrine gland:
• Composed of one cell
• Goblet cell
• Multicellular exocrine gland:
• Composed of many cells
• Sweat glands, salivary glands, etc.
• Simple and compound
40

Shapes of Exocrine Glands
n Branching
n Simple
n Compound
n Shape
n Tubular
n Alveolar
n Tubuloalveolar

Structural Types of
Exocrine Glands
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Tissue surface
Duct
Secretory portion
Simple tubular Simple branched
tubular
Simple coiled
tubular
Simple branched
alveolar
Compound tubular
Compound alveolar
42

Types of Glandular
Secretions
• Merocrine Glands
• Fluid product
• Salivary glands
• Pancreas gland (?)
• Sweat glands
• Serous Fluid
• Mucus
• Apocrine Glands
• Cellular product
• Portions of cells
• Mammary glands
• Ceruminous glands
Pinched off
portion of cell
(secretion)
• Holocrine Glands
• Secretory products
• Whole cells
• Sebaceous glands
Disintegrating cell
and its contents
(secretion)
New cell
forming by
mitosis and
cytokinesis
(b) Apocrine gland
(c) Holocrine gland
45

Connective Tissue
n Four main types:
n Fibrous
n Loose, ordinary
(areolar)
n Adipose
n Reticular
n Dense
n Irregular
n Regular
(collagenous and elastic)
n Bone
n Compact bone
n Cancellous bone
n Cartilage
n Hyaline
n Fibrocartilage
n Elastic
n Blood

Fibrous connective tissue
n Loose, ordinary (areolar) connective tissue
n One of the most widely distributed of all tissues
n Intercellular substance is prominent and consists
of collagenous and elastic fibers loosely interwoven
and embedded in soft, viscous ground substance
Function—stretchy, flexible connection

Fibrous connective tissue
n Adipose tissue
n Similar to loose connective tissue but contains
mainly fat cells
n Functions—protection, insulation, support,
and food reserve

Fibrous connective tissue
n Reticular tissue
n Forms framework of spleen, lymph nodes, and bone
marrow
n Consists of network of branching reticular fibers with
reticular
cells overlying them
n Functions—defense against microorganisms and other
injurious substances; reticular meshwork filters out
injurious particles, and reticular cells phagocytose
them

Dense fibrous tissue
n Matrix consists mainly of fibers packed
densely and relatively few fibroblast cells
n Irregular—fibers intertwine irregularly to
form a thick mat
n Regular—bundles of fibers are arranged
in regular, parallel rows
n Collagenous—mostly collagenous
fibers in ECM
n Elastic—mostly elastic fibers in
ECM

Dense fibrous tissue
n Locations—composes structures that
need great tensile strength, such as
tendons and ligaments; also dermis
and outer capsule of kidney and
spleen
n Function—furnishes flexible
connections that are strong or
stretchy

Bone tissue
n Highly specialized connective tissue type
n Cells—osteocytes—embedded in a calcified matrix
n Inorganic component of matrix accounts for 65%
of total bone tissue
n Functions:
n Support
n Protection
n Point of attachment for muscles
n Reservoir for minerals
n Supports blood-forming tissue

Compact bone
n
n
Osteon (Haversian system)
n
n
n
n
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:
n
n
n
Osteocyte—mature, inactive bone cell
Osteoblast—active, bone-forming cell
Osteoclast—bone-destroying cell
n Formation (ossification) (Figure 5-24)
n
n
In membranes—e.g., flat bones of skull
From cartilage (endochondral)—e.g., long bones, such as the humerus

Cancellous bone
n Trabeculae—thin beams of bone
n Supports red bone marrow
n Myeloid tissue—a type of reticular tissue
n Produces blood cells
n Called spongy bone because of its spongelike
appearance

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

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

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

Blood (cont.)
n Functions
n Transportation
n Regulation of body temperature
n Regulation of body pH
n White blood cells destroy bacteria
n 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 Tissues
• General characteristics:
• Muscle cells also called
muscle fibers
• Contractile
• Three (3) types:
• Skeletal muscle
• Smooth muscle
• Cardiac muscle
• Skeletal muscle
• Attached to bones
• Striated
• Voluntary
• Smooth muscle
• Walls of organs
• Skin
• Walls of blood vessels
• Involuntary
• Non-striated
• Cardiac muscle
• Heart wall
• Involuntary
• Striated
• Intercalated discs
72

Microscopic
Characteristics

Nervous Tissue
n Functions—rapid regulation and integration
of body activities
n Specialized characteristics
n Excitability
n Conductivity
n Organs
n Brain
n Spinal cord
n Nerves

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

Tissue Repair
n Tissues have a varying capacity to repair
themselves; damaged tissue regenerates
or is replaced by scar tissue
n Regeneration—growth of new tissue
Scar—dense fibrous mass; unusually thick
scar is a keloid
n Epithelial and connective tissues have the
greatest ability to regenerate
n Muscle and nervous tissues have a limited
capacity to regenerate