Biol 2041 Chapters 16-20 Study Guide

Chapter $16$: Special Senses

• Sensory Receptors: Visual and auditory structures (Section $16.2$).

• Eye Accessory Structures:
    - Eyebrows: Provide protection and shading.
    - Palpebra: Eyelids that protect and moisten the eye.
    - Eyelashes: Help keep debris out of the eyes.
    - Tarsal Glands: Produce oil to minimize tear evaporation.
    - Conjunctiva: Mucous membrane that protects the surface of the eye.
    - Lacrimal Apparatus: Lacrimal gland produces tears for lubrication.
    - Extrinsic Eye Muscles: Control eye movement.

• Fibrous Layer: Composed of:
    - Sclera: The white outer part of the eyeball.
    - Cornea: The transparent front part that refracts light.

• Vascular Layer: Composed of:
    - Choroid: Supplies nutrients to the retina.
    - Ciliary Body: Changes the shape of the lens for focusing.
    - Iris: Contains the pupil, regulates light entry.

• Inner Layer: Includes:
    - Optic Nerve: Transmits visual information to the brain.
    - Retina: Contains two types of photoreceptors:
      - Cone Cells: Responsible for color vision.
      - Rod Cells: Responsible for low-light vision.

• Lens and Fluids: Lens focuses light on the retina; works with aqueous humor and vitreous humor for vision clarity.

• External Ear: Made up of:
    - Auricle (Pinna): Visible part of the ear.
    - External Auditory Meatus: Canal leading to the eardrum.
    - Tympanic Membrane: Eardrum that vibrates with sound.

• Middle Ear: Contains:
    - Auditory Ossicles: Malleus, incus, stapes transmit vibrations to the inner ear.
    - Pharyngotympanic Tube: Equalizes pressure in the ear.

• Inner Ear: Includes:
    - Cochlea: Transforms sound vibrations into neural signals.
    - Vestibule: Involved in balance.

Chapter $17$: Endocrine System

• System Functions: Regulates body activities through hormones, similar to nervous system.

• Hormone Classification: Hormones classified chemically; they interact specifically with target cells.

• Secretion Control: Governed by:
    - Hormonal Stimuli: Hormones from other glands.
    - Humoral Stimuli: Changes in blood levels of certain ions or nutrients.
    - Neural Stimuli: Nerve fibers stimulate hormone release.
    - Feedback Loops: Utilizes positive and negative feedback mechanisms to maintain homeostasis.

• Hypothalamus: Key control center regulating the endocrine organs.

• Pituitary Gland: Found in the sella turcica; secretes various hormones with distinct roles.

• Thyroid Gland: Produces hormones that regulate metabolism.

• Adrenal Gland: Composed of two sections:
    - Cortex: Produces steroid hormones.
    - Medulla: Produces catecholamines (epinephrine and norepinephrine).

• Gonads: Organs (ovaries/testes) with distinct endocrine functions related to reproduction.

Chapter $18$: Blood

• Whole Blood: Comprised of plasma and formed elements.

• Hematocrit: Volume percentage of erythrocytes in blood samples.

• Plasma: Contains major proteins:
    - Albumin: Maintains osmotic pressure.
    - Globulins: Involved in immune response.
    - Fibrinogen: Important for blood clotting.

• Formed Elements: Includes:
    - Erythrocytes: Red blood cells for oxygen transport.
    - Leukocytes: White blood cells for immune response.
    - Platelets: Cell fragments that aid in clotting.

• Hematopoiesis: Blood cell formation in red bone marrow, distinct from yellow marrow.

Chapter $19$: Heart

• Anatomy: Located in the mediastinum; characterized by a base and apex.

• Pericardium: Protective sac surrounding the heart.

• Heart Wall: Composed of three layers:
    - Epicardium: Outer layer.
    - Myocardium: Muscular layer responsible for heart contractions.
    - Endocardium: Inner lining of the heart.

• Chambers and Vessels: Contains four chambers:
    - Atria: Upper chambers for receiving blood.
    - Ventricles: Lower chambers for pumping blood.
    - Major vessels include arteries and veins conducting blood.

• Valves: Four heart valves regulating blood flow throughout the heart.

• Circulation Paths: Include three main circuits:
    - Pulmonary: Blood to and from lungs.
    - Systemic: Blood to and from the body.
    - Coronary: Supplying blood to the heart itself.

• Physiology: Heartbeat characterized by systole (contraction) and diastole (relaxation).

• Cardiac Muscle: Contains intercalated disks and specialized conduction system regulating heartbeat.

Chapter $20$: Blood Vessels

• Vessel Walls: Composed of three layers (tunicae); large vessel walls supplied by vaso vasorum.

• Arteries: Classified into three types:
    - Elastic: Large vessels near the heart.
    - Muscular: Distributing arteries.
    - Arterioles: Smaller branches.

• Capillaries: Three types regulation permeability in tissue:
    - Continuous: Least permeable, common in muscle and skin.
    - Fenestrated: More permeable; found in kidneys and intestines.
    - Sinusoid: Highly permeable; found in the liver and spleen.

• Veins: Thinner walls compared to arteries; include valves to prevent backflow.

• Circuits: Major vessels serving:
    - Pulmonary Circuit
    - Systemic Circuit (includes aorta and vena cava)
    - Coronary Circuit

• Vascular Anastomoses: Blood vessel connections providing alternate pathways.

• Portal System: Unique system where blood flows through two capillary beds before returning to the heart.