CHAPTER 40

• Epithelial tissue can be classified based on:

  • Size: squamous (regularly shaped), cuboidal (boxy appearance), columnar (rectangular)
  • Number of layers of the cell: simple (one layer), stratified (2 or more layers), pseudostratified (seems to have several layers but only has 1 layer)
• Frog skin is classified as simple squamous - irregularly shaped

  • Respiratory function (gas exchange on the skin) - always wet not just because of their environment
  • Some frogs have a thicker layer of the epithelial layer, which is why it appears stratified
  • Even if it’s stratified, it may not exceed a few layers to retain its respiratory function
  • Three excretory glands:
  • Poison Gland: for defense against predators, has a duct that leads to the outside
  • Mucous gland: secretory function - mucus, duct within the epidermis
• • Seromucous gland: same function as mucous gland - watery secretions
• Human squamous epithelium (cheek cell) has a digestive function

  • The structure corresponds to its function (stratified)
• Large intestine:

  • Simple columnar
  • Only have one layer attached to the basal layer of the epithelial tissue
  • Have goblet cells, glands that secrete mucin to lubricate the large intestine to protect it from processed food materials
  • Columnar - optimal for absorption if there are nutrients that can be absorbed in processed food mats
  • Muscularis - Component of smooth muscle
• Human Kidney:

  • Simple cuboidal
  • For blood filtration
  • Malpighian body (renal corpuscle) after blood enters the nephron, it goes here
  • It contains the glomerulus (cluster of capillaries that absorb protein from the blood) the remaining fluid will pass through the bowman’s capsule
• Sweat glands:

  • Cuboidal
  • As opposed to the single layer for the kidney, it’s stratified
  • Has excretory and secretory segments
  • Excretory - product of the gland is excreted outside the body
  • Secretory- within the body; mucus and some hormones are secretory and produced by different glands
• Urinary bladder:

  • Pseudostratified - all cells - connected to the basal layer
  • Transitional epithelium - can change the shape
  • Its function is to store urine, which may be extended/expanded if full
• Mammary gland:

  • Stratified - many layers
  • Squamous - irregular shape
  • Active - being used to feed the young
  • Subject to abrasion/stress
  • The epithelial cells on the basal cells are actively dividing
  • The cells being pointed out are being sloughed off
  • Being replaced - older cells - pushed up when it's being replaced by younger cells in the basal layer
• Artery and Vein:

  • Simple squamous because they are part of the circulatory system which is linked to the respiratory system so simple gas exchange must be readily available
  • Difference in terms of muscular layer of the artery - experiences a wave of pressure when pumping blood from the heart unlike the vein (which doesn't need to be robust)
• Loose connective Tissue:

  • Attaches a tissue to another tissue, and is for support
  • Thin covering of muscle
  • Extracellular matrix - where components are embedded
  • Most have fibers - three different types:
  • Elastic fiber
  • Collagen fiber
  • Reticular fiber
• Tendons:

  • Types of fiber
  • Function - attaches the muscles to the bone
  • Has fibroblasts (undifferentiated cells), which can develop later on as tendons that are rich in collagen
  • Tendons are easily damaged which necessitates fibroblasts
• Hyaline cartilage:

  • The cells are referred to as chondrocytes, which secretes the matrix where the cartilages are
  • Lacunae - cavity
  • Perichondrium - covering
• Human Blood smear:

  • A slide that requires skill - blood is smeared with a cover slip
  • Before the blood clots, it should be smeared
  • Plasma - extracellular matrix of the blood
• Adipose tissue:

  • Composed of adipocytes - cyte - cell
  • Its main function is to store fats and lipids
  • Each adipocyte cell have stored lipids inside them
  • Can change in size
• Bone Decalcified:

  • Osteon - unit of the bone
  • Bone - considered a mineralized connective tissue
  • As the individual matures, it forms deposits of minerals like phosphates, magnesium, etc - bones solidify for vertebrates
  • Haversian canal - cavity at the middle
  • Several smaller cavities - lacuna/e
• Skeletal muscle:

  • Presence of striations
  • Multiple nuclei - based on the embryonic tissue where it’s derived
  • The nuclei turns flat
  • Endomysium is the covering of the skeletal muscle
• Smooth Muscle:

  • Don't have striations at all
  • Responsible for involuntary movement
• Cardiac muscle:

  • Found in the tissues of the heart
  • Has striations
  • Presence of the intercalated disc
  • Each muscle fiber has these discs for the conduction of electrical impulses of the heart
• Nervous Tissue:

  • Neurons (main nervous tissue) and neuroglial cells (support)
  • Neurons transmit and receive signals
  • Dendrites - signal passes through here
  • Away from the neuron - axon
• Hydra has a very simple body plan with a mouth and a gastrovascular cavity
• In flat animals like tapeworms, most cells are in direct contact with their environment
• More complex organisms are composed of compact masses of cells with a more complex internal organization
• Evolutionary adaptations enable sufficient exchange with the environment
• An idealized complex animal has body systems including digestive, circulatory, respiratory, and excretory systems
• The digestive system has folds with microvilli in the small intestine to increase surface absorption
• The circulatory system is tied with the respiratory system
• The lung tissue has only one layer of cells for gas exchange
• The excretory system has highly folded structures in the blood vessels of the kidney
• In animals, the space between cells is filled with interstitial fluid, linking exchange surfaces to body cells
• A complex body plan helps an animal living in a variable environment to maintain a relatively stable internal environment
• Most animals are composed of cells organized into tissues, which make up organs and systems
• Organs like the pancreas belong to more than one organ system
• The main components and functions of organ systems in mammals include:

  • Digestive system: Food processing
  • Circulatory system: Internal distribution of materials
  • Respiratory system: Gas exchange
  • Immune and lymphatic system: Body defense
  • Excretory system: Disposal of metabolic wastes
  • Endocrine system: Coordination of body activities
  • Reproductive system: Gamete production
  • Nervous system: Coordination of body activities
  • Integumentary system: Protection
  • Skeletal system: Body support
  • Muscular system: Locomotion
• The four main types of animal tissues are epithelial, connective, muscle, and nervous
• Epithelial tissue covers the outside of the body and lines organs and cavities within the body
• Connective tissue holds many tissues and organs together and contains sparsely packed cells scattered throughout an extracellular matrix
• Muscle tissue is responsible for nearly all types of body movement and consists of filaments of actin and myosin
• Nervous tissue functions in the receipt, processing, and transmission of information and contains neurons/nerve cells and glial cells/glia
• Skeletal muscle is responsible for voluntary movement and has striations