Digestive System

Overview of the Digestive System

The digestive system is responsible for the breakdown of food, absorption of nutrients, and elimination of waste. It consists of the alimentary canal and accessory organs.

• Extrinsic Nerve Supply: Nerves outside the digestive tract that regulate motility and secretion, primarily via the autonomic nervous system (sympathetic and parasympathetic fibers).

Stomach

• Divisions: Cardia, fundus, body, and pylorus.

• Sphincters: Lower esophageal (cardiac) sphincter and pyloric sphincter control entry and exit of food.

• Gastric Mucosa: The innermost layer, containing gastric glands that secrete digestive enzymes and hydrochloric acid.

• Epithelial Lining Folds: Rugae are folds that allow the stomach to expand.

• Gastric Glands and Secretions: Parietal cells (HCl), chief cells (pepsinogen), mucous cells (mucus), and enteroendocrine cells (hormones).

Small Intestine

• Subdivisions: Duodenum, jejunum, ileum.

• Valves: Ileocecal valve controls flow into the large intestine.

Large Intestine

• Divisions: Cecum, colon (ascending, transverse, descending, sigmoid), rectum, anal canal.

Anal Canal

• Sphincters: Internal (involuntary, smooth muscle) and external (voluntary, skeletal muscle) anal sphincters control defecation.

Liver

• Secretion: Produces bile, which emulsifies fats for digestion.

• Function: Metabolism, detoxification, storage of nutrients, and synthesis of plasma proteins.

• Portal Triad: Consists of a branch of the hepatic artery, portal vein, and bile duct.

Pancreas

• Main Pancreatic Duct Opening: Delivers pancreatic juice to the duodenum.

• Secretions:

  • Endocrine: Insulin and glucagon (regulate blood glucose).

  • Exocrine: Digestive enzymes and bicarbonate.

Urinary System

Kidney Anatomy and Function

• Internal Structures: Cortex, medulla, renal pyramids, renal pelvis.

• Function: Filtration of blood, removal of waste, regulation of fluid and electrolyte balance.

Urinary Bladder and Urethra

• Urinary Bladder: Stores urine until excretion.

• Urethra: Conducts urine from bladder to outside the body.

The Nephron

• Parts (in order): Renal corpuscle (glomerulus + Bowman's capsule), proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct.

Processes in Urine Formation

• 1. Filtration

• 2. Reabsorption

• 3. Secretion

Urine Composition

• Water, urea, creatinine, ions (Na+, K+, Cl-), and other waste products.

Male Reproductive System

Testis Structure and Function

• Structure: Seminiferous tubules (sperm production), interstitial cells (testosterone production).

• Function: Spermatogenesis and hormone secretion.

Male Accessory Glands

• Seminal vesicles, prostate gland, bulbourethral glands (produce seminal fluid components).

Hormonal Regulation

• Hypothalamic-pituitary-gonadal axis regulates testosterone and sperm production.

Female Reproductive System

Ovaries Structure and Function

• Structure: Ovarian follicles at various stages of development.

• Function: Oogenesis and hormone secretion (estrogen, progesterone).

Uterus and Fallopian Tubes

• Uterus: Site of implantation and fetal development.

• Fallopian Tubes: Transport oocyte from ovary to uterus; site of fertilization.

Hormonal Regulation

• Regulated by hypothalamic-pituitary-ovarian axis (FSH, LH, estrogen, progesterone).

The Endocrine System

Classification of Hormones

• By Function: Tropic (regulate other glands), non-tropic (direct effects).

• By Chemical Structure: Steroid hormones (e.g., cortisol, aldosterone, estrogen, testosterone), peptide hormones, amines.

Regulation of Hormone Secretion

• Negative feedback is the primary mechanism.

Pituitary Gland

• Connection to Brain: Connected to hypothalamus via infundibulum.

• Function of Prolactin: Stimulates milk production.

• Hormones of Posterior Pituitary: Oxytocin, antidiuretic hormone (ADH).

Hormones of Adrenal Cortex

• Glucocorticoids (cortisol), mineralocorticoids (aldosterone), androgens.

Hormones of Parathyroid

• Parathyroid hormone (PTH) regulates calcium levels.

Introduction to Anatomy

Levels of Structural Organization

• Chemical, cellular, tissue, organ, organ system, organismal levels.

Body Planes and Sections

• Sagittal, frontal (coronal), transverse (horizontal) planes.

Body Cavities

• Dorsal (cranial, vertebral), ventral (thoracic, abdominopelvic).

Abdominopelvic Regions and Organs

• Divided into nine regions (e.g., epigastric, umbilical, hypogastric) for anatomical reference.

The Cell

Cytoplasmic Organelles

• Nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes.

Chromosomes

• Structures composed of DNA and proteins; carry genetic information.

Bone and Osseous Tissue

Types of Cartilage

• Hyaline, elastic, fibrocartilage.

Parts of a Long Bone

• Diaphysis (shaft), epiphyses (ends), metaphysis, articular cartilage, periosteum, medullary cavity.

Composition of Bone Matrix

• Organic (collagen fibers) and inorganic (hydroxyapatite) components.

Microscopic Structure of Bone

• Osteons (Haversian systems), lamellae, lacunae, canaliculi, central canal.

Epiphyseal Plate (Bone Development)

• Site of longitudinal bone growth during development.

Bone Marrow

• Red marrow (hematopoiesis), yellow marrow (fat storage).

The Skeleton

Axial Skeleton

• Skull, vertebral column, rib cage.

Cranial Bones and Sutures

• Eight cranial bones joined by immovable joints called sutures.

Fetal Skull Fontanelles

• Soft spots that allow for growth and compression during birth.

Sternum and Coxal Bone

• Sternum: Breastbone in the thorax.

• Coxal bone: Hip bone, part of the pelvic girdle.

Myology (Muscle System)

Muscle Actions

• Agonist, antagonist, synergist, and fixator roles in movement.

Naming Skeletal Muscles

• Based on location, shape, size, direction of fibers, number of origins, and action.

Important Skeletal Muscles

• Examples: Biceps brachii, quadriceps femoris, deltoid, etc.

The Heart

Layers of the Heart Wall

• Epicardium (outer), myocardium (muscular middle), endocardium (inner).

Chambers of the Heart

• Right and left atria, right and left ventricles.

Heart Valves

• Atrioventricular (tricuspid, bicuspid/mitral) and semilunar (pulmonary, aortic) valves.

Cardiac Conduction System

• Sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, Purkinje fibers.

Blood

Blood Composition

• Plasma (liquid matrix) and formed elements (RBCs, WBCs, platelets).

Blood Plasma

• Water, proteins (albumin, globulins, fibrinogen), nutrients, hormones, waste products.

Blood Volume

• Average adult: 4-6 liters.

Red Blood Cells (RBCs)

• Carry oxygen via hemoglobin; biconcave shape increases surface area.

Leukocytes (WBCs)

• Granulocytes: Neutrophils, eosinophils, basophils.

• Agranulocytes: Lymphocytes, monocytes.

• Functions: Immune defense, phagocytosis, antibody production.

• Increase/Decrease: Leukocytosis (increase), leukopenia (decrease).

Hemolytic Disease of the Newborn

• Occurs when maternal antibodies attack fetal RBCs (often due to Rh incompatibility).

Genetics

Key Definitions

• Gene: Unit of heredity.

• Allele: Alternative form of a gene.

• Genotype: Genetic makeup.

• Phenotype: Observable traits.

Punnett Square

• Tool to predict genetic crosses and offspring ratios.

X-Linked Inheritance

• Genes located on the X chromosome; examples include hemophilia and color blindness.

Additional info: Some explanations and examples were expanded for clarity and completeness.