A&P-tissues

Histology

the study of tissues and how they are arranged in organs

What is the matrix also termed?

ground subtance

Tissue

a group of similar cells and cell products working together to perform a specific role in an organ

What is the matrix composed of?

fibrous proteins and ground substance

What do the tissue types differ from each other in?

1. types and functions of cells

2. matrix features

3. space occupied by cells versus matrix

What are the main characteristics of epithelial tissue?

1. closely packed cells (few matrix)

2. avascular (not own blood supply)

3. presence of basement membrane

4. high rate of regeneration and cell division

5. covers body surfaces and cavities

6. upper surface exposed to environment

What are the two main types of epithelial tissue?

simple (one layer)

stratified (multiple layers)

Goblet cells

wineglass shaped mucus secreting cells located in simple columnar and pseudostratified epithelium

Simple squamous epithelium

• single row of flat cells

• secretes serous fluid

• very thin tissue

function: permits rapid diffusion of substances

location: alveoli (lungs), blood vessels, capillaries

Simple cuboidal epithelium

• single layer of square cells

function: absorption and secretion, mucus production, and movement

location: liver and glands

Simple columnar epithelium

• single row of tall and narrow cells

• brush border of microvilli (also goblet cells)

function: absorption and secretion (nutrients)

location: digestive tract

Pseudostratified epithelium

• looks multilayered yet all cells touch basement membrane

• cilia (goblet cells)

function: secretes and propels mucus

location: respiratory tract

Keratinized stratified epithelium

• cells become flat and scaly toward surface

• dead cells

function: resists abrasion and retards water loss

location: epidermis of skin, palms and soles

Non-keratinized stratified epithelium

• lacks surface layer of dead cells

function: resists abrasion

location: oral mucosa, esophagus, vagina

Stratified squamous epithelium

most widespread and deepest tissue that functions for protection

ex. two kinds (keratinized and non-keratinized)

Stratified cuboidal epithelium

• multiple layers with square cells

• secretes sweat, produces sperm

function: protection

locations: glands and ducts

Urothelium (transitional epithelium)

• surface cells change from round to flat (when stretched)

• contains cuboidal and squamous cells

• surface cells form “umbrellas” to protect from acidity of urine

function: stretches to fill urinary tract

location: ureter and bladder

Connective tissue characteristics

• abundant type of tissue

• cells occupy less space than matrix

• vascular

• cells far apart

Connective tissue fibers

• collagen

most abundant type that is tough and resists stretching

function: binds

• reticular

thin fibers coated with glycoprotein layer

function: forms shape of organs

• elastic

very thin fibers made of protein elastin

function: allows for stretch and recoil

What are the two types of fibrous connective tissue?

loose fibrous (few fibers)

dense fibrous (many fibers)

Areolar connective tissue

loose tissue

• all three fibers

function: allows diffusion of blood vessels and nerve supply

location: beneath epithelial tissue and within empty spaces

Reticular connective tissue

loose tissue

• reticular fibers

function: forms framework for lymphatic organs

location: found in organs needing shape i.e. spleen

Dense regular connective tissue

dense tissue

• wavy and regular pattern

• collagen fibers

function: used for binding purposes

location: ligaments (bone to bone) and tendons (muscle to bone)

Dense irregular connective tissue

dense tissue

• random pattern

• collagen fibers

function: protection

location: dermis, capsules around organs

Adipose tissue

fatty tissue in which adipocytes are the dominant cell type

ex. nonliving substance is surrounded by areolar connective tissue

What are the two types of fat and their functions?

1. white fat

fat found in adults

serves to cushion organs such as the eyeballs and kidneys

2. brown fat

fat found in children

functions as a heat generation tissue and is filled with mitochondria

Do we all have the same number of adipocyte cells?

yes, some people just have increased sizes

What are the functions of fat?

1. provides protection

2. keeps homeostasis of temperature

Cartilage

stiff avascular connective tissue with flexible matrix

three types: hyaline, elastic, and fibrocartilage

location: gives shape to ear, tip of nose, and larynx

What are the cells of cartilage?

• chondroblasts

immature cells that produce matrix

• chondrocytes

mature cells that get trapped in lacunae

ex. chondroblasts become chondrocytes

Perichondrium

sheath of dense irregular connective tissue that surrounds membranes, providing them with nutrients from blood vessels

Why does cartilage have a slow healing rate?

because it is an avascular tissue

Hyaline cartilage

glassy appearance with a tough layer

fibers: thin collagen fibers

location: trachea, larynx, and fetal skeleton

Elastic cartilage

stretchy cartilage covered with perichondrium

fibers: elastic

location: external ear

Fibrocartilage

fibers: large collagen fibers

location: intervertebral discs

What is the matrix or nonliving substance of cartilage abundant in?

GAGs

function: make tissue resistant to heavy pressure

Blood

fluid connective tissue that transports cells and matter from various places

Plasma

blood’s ground substance

What is blood composed of?

formed elements and ground substance

What are the formed elements of blood?

• erythrocytes (RBCs)

transport gases (oxygen and carbon dioxide)

• leukocytes (WBCs)

neutrophils, eosinophils, basophils, lymphocytes, monocytes

fight infection and disease

• platelets (thrombocytes)

fragments of big cells that form blood clots

Nervous tissue

tissue specialized for communication via electrical and chemical signals

What are the two cell types of nervous tissue?

• neurons

detect, transmit, and respond to stimuli

• glial cells

protect and assist the neurons

What are the neuron parts?

• neurosoma (cell body)

integrates data

• dendrites

receive and transmit data

• axon (nerve fiber)

sends outgoing signals

What are the two excitable tissues?

muscular and nervous tissue

Excitability

the ability to sense and respond to stimulation

Muscular tissue

tissue specialized for contraction in response to stimulation

function: helps with body movement and provides a source of heat

Skeletal muscle tissue

made of muscle fibers (long thin cells)

• striated

• voluntary

• multinucleated

location: attached to bone

Cardiac muscle tissue

contains cardiomyocyte cells

• mononucleated

• striated (intercalated discs)

• involuntary

location: attached to heart wall

Smooth muscle tissue

made of fusiform (spindle-shaped) cells

• lacks striations

• involuntary

location: walls of viscera (hollow organs)

Tight junctions

interlocking linkage of cell membrane between two cells that is securely attached and prevents leakage of substances

ex. mechanical junction

location: digestive tract

Desmosomes

strong glue-like connection that hold cells together

ex. mechanical junction

location: skin and heart

Gap junctions

a communicating junction that allows passage of ions, nutrients, and cytoplasm

ex. electrical junction

location: cardiac muscle, and eye features

Glands

cells or organs that secrete or release substances in the body

Secretion vs. Excretion

secretion uses useful substances while excretion uses waste products

Endocrine gland

• no ducts

• infiltrate with blood vessels

• secrete hormones

Exocrine glands

• contain ducts

• secretes to surface

• secretes enzymes + specific names

Serous glands

produce watery secretion (tears)

Mucous glands

secrete mucus (goblet cells)

Mixed glands

secrete both serous and mucous substances

Eccrine (merocrine) secretion

uses vesicles

secretes ONLY SECRETION

ex. tear glands

Apocrine secretion

secretes secretion and part of cytoplasm/membrane

ex. milk fat from mammary glands

Holocrine secretion

secretes secretion and whole cell

ex. oil glands

Mucous membrane

lines passages open to external environment

consists of pseudostratified columnar epithelium based on areolar connective tissue

ex. located in digestive and respiratory tract

Serous membrane

secretes watery fluid within internal membranes

consists of simple squamous epithelium based on areolar connective tissue

ex. covers organs and lines walls of body cavities

Hyperplasia

tissue growth through cell multiplication

Hypertrophy

tissue growth through enlargement of preexisting cells

ex. muscle growth through exercise

Neoplasia

development of a tumor

Differentiation

the development of a more specialized form and function by unspecialized tissue

Metaplasia

a change from one type of mature tissue to another

Regeneration

replacement of dead or damaged cells by the same type as before

ex. repair of minor skin or liver injuries

Fibrosis

replacement of damaged cells with scar tissue

does not restore normal function

ex. repair of severe cuts and burns

Atrophy

shrinkage of tissue through loss in cell size or number

Necrosis

pathological tissue death due to trauma, toxins, or infections

types: infarction and gangrene

Apoptosis

programmed cell death

ex. normal cell death

What are the different epithelial cell types?

four types

• simple squamous

  • thin, scaly cells

• simple cuboidal

  • square or round cells

• simple columnar

  • tall, narrow cells

• pseudostratified columnar

  • some cells taller than other

• goblet cells