Body Tissues And Membranes

 

I.                  Body Tissues

A.   Epithelial Tissue

1.   Functions

a.   Forms sheets over exterior and interior surfaces

b.    Absorption -

c.    Secretion – glandular

(1)           Exocrine

(2)           Endocrine

2.   Specializations

a.   Microvilli

b.    Cilia

3.   Classification

a.   By shape

(1)           Squamous

(2)           Cuboidal

(3)           Columnar

b.    By layers

(1)           Simple

(2)           Stratified

(3)           Psuedostratified

B.   Connective Tissue

1.   Functions

a.   Binds structures together

b.    Protection and support

c.    Fills spaces

d.    Produces blood cells

e.   Stores fat

2.   Composition

a.   Cells

b.    Matrix

(1)           (Ground substance) – water + solutes (small proteins, gags etc)

(2)           Fibers

·       Collagen (white)

·       Elastin (yellow)

·       Reticular – collagenous but very thin, branched, form delicate supporting networks

3.   Types

a.   Loose connective tissue (aerolar)

(1)           Cells are fibroblasts, not packed close together

(2)           Matrix is jelly-like, contains collagen and elastin fibers

(3)           Adipose – fat storage, limited amounts of matrix

(4)           Reticular CT – only reticular fibers, found in lymphoid organs and tissues, store and/or produce white blood cells

b.    Fibrous connective tissue

(1)           Fibroblasts with tightly packed collagenous fibers

(2)           Strong, not much (ground substance)

(3)           Tendons – connect muscles to bone

(4)           Ligaments – connect bones to other bones (at joints)

(5)           Relatively poor blood supply (slow healing)

c.    Cartilage

(1)           Chondrocytes in a gel-like matrix (solid but flexible)

(2)           Chondrocytes in lacunae

(3)           High water content but avascular (slow or no healing)

(4)           Hyaline – fine collagen fibers, glassy appearance

·       nose

·       ends of long bones and ribs

·       supporting rings of trachea

·       fetal skeleton

(5)           Elastic – matrix contains lots of elastic fibers (with collagen), more flexible than hyaline

·       outer ear

(6)           Fibrocartilage – strong cartilage fibers, absorbs shock and reduces friction between joints

·       vertebral disks

·       knees

d.    Bone – mineralized matrix, calcium salts around protien fibers

(1)           Compact bone

·       Haversian systems (osteons) – osteocytes in lacunae, concentric cylinders

·       Central canals – contain nerve fibers and blood vessels

·       Canaliculi – connect lacunae

(2)           Spongy bone

·       Bars and plates (spicules) of bone

·       Spaces filled with red marrow

e.   Blood

(1)           Matrix is fluid – plasma

(2)           Matrix is not made by cells, unlike other CTs

(3)           Fibers are soluble - fibrinogen

C.  Muscular Tissue – cells (called fibers in skeletal muscle) containing actin and myosin filaments.  These are contractile; muscle cells contract and produce movement.

1.   Skeletal

a.   Attached to bone, move skeleton

b.    Multinucleated, long cells called fibers

c.    Voluntary

d.    Striated

2.   Smooth

a.   Visceral

b.    Single nucleus, spindle shaped cells

c.    Involuntary

d.    Non-striated

3.   Cardiac

a.   Heart

b.    Cylindrical, branched

c.    Involuntary

d.    Striated

e.   Intercalated disks

D.  Nervous Tissue

1.   Brain and spinal cord

2.   Neurons

a.   Dendrite

b.    Cell body

c.    Axon

(1) Long axons are nerve fibers

3.   Glial (neuroglial) cells

a.   Supporting cells

b.    Schwann cells

(1)           Neurilemma

(2)           Myelin sheath

(3)           Nodes of Ranvier

 

II.               Body Membranes

A.    Mucous Membranes – line interior walls of organs and tubes that open to the outside of the body (the inside of the doughnut)

1.   Epithelium over CT

2.   Goblet cells interspersed throughout

a.   Specialized to secrete mucus

b.    Mucus is protective; traps bacteria and other foreign particles, protects upper GI from digestive juices

c.    Ulcers result from inadequate mucus production in GI

 

B.   Serous Membranes – line thoracic and abdominal cavities, cover organs

1.   Continuous double layered membrane

2.   Simple squamous epithelium over CT

3.   Serous fluid between membranes reduces friction

4.   Help support organs and compartmentalize cavities

5.   Visceral membrane – layer next to organ

6.   Parietal membrane – layer next to abdominal or thoracic wall

7.   Mesentery – place where parietal and visceral membranes come together

8.   Examples: pleural membranes, pericardium, peritoneum, greater (intestines) and lesser omentum (between stomach and liver)

9.   Peritonitis

 

C.   Synovial Membranes – line freely moveable joint cavities

1.   Produce synovial fluid

2.   Rheumatoid arthritis – inflammation, fibrosis, thickening, eventually the bones that come together at the joint may fuse

 

D.   Meninges – line dorsal cavity, 3 layers

1.   Composed of CT

2.   Cover brain and spinal cord

3.   Meningitis

 

E.   Cutaneous Membrane – the skin

1.   stratified squamous epithelium over thicker layer of CT

 

III.            Medical Focus: Classification of Cancers

A.   Carcinomas – arise from epithelial tissues

B.   Sarcomas – arise from muscle and CT

C.  Leukemias – blood cells

D.  Lymphomas – arise in reticular CT (lymphoid tissue)

E.   Screening

1.   Pap smear – (George Papanicolaou) cervical epithelium (opening of the uterus) obtained with a swab and cells examined for abnormal changes

2.   Biopsy – removal of tissue with a plunger-like device

3.   Pathologist – a physician who studies disease

4.   Diagnosis – identification of a disease