are Tissues
Tissues groups of cells that are similar in structure and function Histology the study of tissues The four basic tissue types are: 1) Epithelial 2) Connective 3) Muscle 4) Nervous
Epithelial tissue
Epithelial tissue covers the body, lines body cavities, and forms glands Functions of epithelial tissue (give examples): 1) protection 2) absorption 3) filtration 4) excretion 5) secretion 6) holds nerve endings
Epithelial tissue
Characteristics of epithelial tissue: 1) composed of almost all cells 2) the cells connect tightly by membrane junctions a) tight junctions b) desmosomes c) gap junctions
Epithelial tissue
Characteristics of epithelial tissue: 3) the cells show polarity, with an apical (top) surface and a basal (bottom) surface 4) rests on connective tissue, which provides support and nutrients
Epithelial tissue
Characteristics of epithelial tissue (cont'd):
5) avascular 6) the ability to quickly regenerate when damaged
Epithelial tissue classification
By the number of cell layers simple stratified By cell shape squamous cuboidal columnar
Figure 4.1
Epithelial tissue classification
This scheme gives six categories (with examples): simple squamous the lung alveoli simple cuboidal forming kidney tubules simple columnar lining the GI tract stratified squamous skin stratified cuboidal the ducts of some glands stratified columnar lining the male urethra
Figure 4.3a Epithelial tissues.
(a) Simple squamous epithelium Description: Single layer of flattened cells with discshaped central nuclei and sparse cytoplasm; the simplest of the epithelia.
Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae. Location: Kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).
Air sacs of lung tissue Nuclei of squamous epithelial cells
Photomicrograph: Simple squamous epithelium forming part of the alveolar (air sac) walls (125x).
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Figure 4.3b Epithelial tissues.
(b) Simple cuboidal epithelium Description: Single layer of cubelike cells with large, spherical central nuclei. Simple cuboidal epithelial cells Function: Secretion and absorption. Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface. Basement membrane Connective tissue Photomicrograph: Simple cuboidal epithelium in kidney tubules (430x).
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Figure 4.3c Epithelial tissues.
(c) Simple columnar epithelium Description: Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus secreting unicellular glands (goblet cells).
Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action. Location: Nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.
Simple columnar epithelial cell
Basement membrane Photomicrograph: Simple columnar epithelium of the stomach mucosa (860X).
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Figure 4.3e Epithelial tissues. (e) Stratified squamous epithelium Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers. Stratified squamous epithelium
Function: Protects underlying tissues in areas subjected to abrasion. Location: Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane. Photomicrograph: Stratified squamous epithelium lining the esophagus (285x).
Nuclei Basement membrane Connective tissue
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Epithelial tissue classification
Two special categories
Pseudostratified columnar Transitional
Figure 4.3d Epithelial tissues.
(d) Pseudostratified columnar epithelium Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus secreting cells and bear cilia.
Cilia Mucus of mucous cell
Function: Secretion, particularly of mucus; propulsion of mucus by ciliary action. Location: Nonciliated type in male's spermcarrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.
Pseudo stratified epithelial layer
Trachea
Photomicrograph: Pseudostratified ciliated columnar epithelium lining the human trachea (570x).
Basement membrane
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Figure 4.3f Epithelial tissues.
(f) Transitional epithelium Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on degree of organ stretch.
Transitional epithelium Function: Stretches readily and permits distension of urinary organ by contained urine. Location: Lines the ureters, urinary bladder, and part of the urethra. Basement membrane Connective tissue Photomicrograph: Transitional epithelium lining the urinary bladder, relaxed state (360X); note the bulbous, or rounded, appearance of the cells at the surface; these cells flatten and become elongated when the bladder is filled with urine.
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Epithelial tissue classification
Glands are epithelial in origin, there are two kinds:
Endocrine glands Exocrine glands
Connective tissue
The most common and diverse tissue type Functions:
Bind and connect other tissue types together Protect tissues and organs from damage Insulate the body and certain organs against heat loss (give examples) Move oxygen and nutrients through the body (as blood)
Connective tissue
Characteristics of connective tissue: All kinds develop from mesenchyme The bulk of the tissue is extracellular matrix Most kinds are wellvascularized, with exceptions (explain)
Connective tissue components
Ground substance Fibers of structural protein 3 kinds
Living cells 4 kinds
collagen fibers elastic fibers reticular fibers fibroblast chondroblast osteoblast hemocytoblast
Figure 4.8
Classes of connective tissue
I. CTP loose connective the fibers are dispersed in the matrix; there are 3 kinds: 1) Areolar 2) Adipose 3) Reticular
Figure 4.9a
Figure 4.9b
Figure 4.9c
Classes of connective tissue
Class
I. CTP loose connective (summary)
a. Areolar most all common, 3 fibers b. Adipose few fibers; many fat cells c. Reticular reticular fibers only Soft packing around organs; retains fluid Insulates body; stores fuel; protects Under epithelia; supports capillaries Under skin; in breasts; packs eyeball, kidneys
Function
Location
An internal skeleton Lymph nodes; spleen; for some organs bone marrow
Classes of connective tissue
I.
CTP dense connective the fibers are highly concentrated in the matrix; there are 2 kinds:
1) Dense regular connective tissue 2) Dense irregular connective tissue
Figure 4.9d
Figure 4.9e
Classes of connective tissue
Class
CTP dense connective (summary)
a. Dense regular of parallel collagen fibers Tensile strength in one plane Tendons; ligaments
Function
Location
b. Dense irregular fibers Tensile strength in not parallel three planes
Dermis of skin; fibrous joint capsules
Classes of connective tissue
II. Cartilage
Mature cartilage contains no nerves, or blood vessels, so it heals slowly, if at all. Its resilient quality is explained by the waterholding extracellular matrix. The living cartilage cells (chondrocytes) receive nutrients by diffusion from an overlying sheet of perichondrium.
Classes of connective tissue
II. Cartilage (cont'd)
Chondrocytes reside in the tissue within cavities called lacunae. Cartilage provides a template for the developing bones of the embryo, and makes up the growth plates of the bones in children.
Classes of connective tissue
II. Cartilage there are 3 kinds: 1) Hyaline cartilage 2) Elastic cartilage 3) Fibrocartilage
Figure 4.9f
Figure 4.9g
Figure 4.9h
Classes of connective tissue
Class II. Cartilage (summary) Function Location
a. Hyaline most common, appears glassy
Firm support; resists compression
b. Elastic has more Firm but flexible elastic fibers in matrix support c. Fibrocartilage many collagen fibers Resists compression
Embryonic skeleton; nose; trachea; larynx; costal cartilages; articular cartilages External ear; epiglottis Intervertebral discs; menisci of knee joint; pubic symphysis
Classes of connective tissue
III. Bone The extracellular matrix is composed of collagen fibers and hard calcium salts (Ca3PO4 and CaCO3). Bone is well vascularized. Like cartilage, the living cells (osteocytes) reside in lacunae.
Classes of connective tissue
III. Bone Functions of bone: a) support and protect body organs b) provide levers for skeletal muscle action c) stores calcium d) site of blood cell formation
Figure 4.9i
Classes of connective tissue
IV. Blood The extracellular matrix is plasma. There are no collagen or elastin fibers, only soluble plasma proteins are present. These solidify during the clotting process.
Classes of connective tissue
IV. Blood The living cells include: a) erythrocytes (red blood cells) b) leukocytes (white blood cells) c) platelets, which are actually fragments of much larger cells
Classes of connective tissue
IV. Blood Functions of blood: a) distributes O2, nutrients, and hormones to body cells b) regulates temperature, tissue pH, fluid volumes c) protects against infection with WBCs, part of the immune system
Figure 4.9j
Covering and lining membranes
These are composed of epithelial tissue with a layer of CTP beneath. There are 3 major kinds of covering and lining membranes: 1) Cutaneous membranes the skin
Covering and lining membranes
3 major kinds (cont'd): 2) Mucous membranes line the hollow organs of organ systems that have an external body opening; includes:
Digestive system the lining secretes mucus Respiratory system Urogenital system the lining does not secrete mucus
Covering and lining membranes (cont'd)
3 major kinds (cont'd): 3) Serous membranes line ventral body cavities that do not have an external body opening; includes: Pericardium surrounds the heart (illustrate) Pleura surrounds the lungs Peritoneum surrounds the abdominal organs
Figure 4.12a, b
Figure 4.12c
Muscle Tissue
Muscle tissue is a highly active tissue type that functions in body movement, or in moving substances through the body. It consists of mostly all cells, in which the contractile proteins actin and myosin predominate. Muscle tissue is served by an abundance of blood vessels and nerves.
Muscle Tissue
There are 3 kinds of muscle tissue: 1) Skeletal muscle (voluntary) 2) Cardiac muscle 3) Smooth muscle
involuntary
Figure 4.11a
Figure 4.11b
Figure 4.11c
Kinds of
Muscle tissue
Skeletal
Function
Body movement;
Attached to bones Facial expression and skin
Location
Cardiac Smooth
Pumps blood through the circulatory system Moves substances through the body
In the walls of the heart In the walls of hollow organs
(circulatory, digestive, urinary, reproductive systems)
Nervous tissue
Nervous tissue forms one of the controlling systems of the body, the nervous system, which consists of:
Brain Spinal cord Peripheral nerves
Nervous tissue
The two basic cell types are:
1) Neurons the functional cells of the system, of several kinds. Neurons:
process sensory input from sense organs control motor output to muscles are longlived, amitotic, and have a high metabolic rate.
Nervous tissue
The two basic cell types are: 2) Neuroglia the supporting cells of the system
act in a similar way to connective tissue in other parts of the body, by insulating and protecting the neurons.
Figure 4.10
Repair of damaged tissue The body replaces damaged tissue in two ways: 1) regeneration 2) fibrosis
Repair of damaged epithelial tissue in 3 steps 1) Inflammation 2) Organization 3) Permanent repair
Inflammation
Scab Epidermis
Blood clot in incised wound Inflammatory chemicals
Vein Migrating white blood cell Artery
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Organization
Regenerating epithelium Area of granulation tissue ingrowth Fibroblast Macrophage
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Permanent Repair
Regenerated epithelium
Fibrosed area
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Tissue types and ability to regenerate
Epithelial Bone Good Areolar Dense irregular Smooth muscle
Tendons & Ligaments Fair Skeletal muscle Cartilage Poor Cardiac muscle Nervous Not at all ?
Germ layers the development of tissues
Germ layers are groups of cells in the embryo that are pre destined to give rise to distinctly different tissues in the adult. There are 3 primary germ layers: 1) Ectoderm 2) Endoderm 3) Mesoderm
Germ layers the development of tissues
In the very early embryo there are cells that have not yet differentiated into the 3 germ layers. They have the ability to become almost any cell type in the adult. What is the name of these cells?