Human Anatomy: Digestive, Connective Tissues, and More
The Human Body: Anatomy and Physiology
Digestive System
The digestive system consists of the gastrointestinal tract (alimentary canal) and accessory digestive organs. The stages of digestion include:
- Ingestion: Food enters the mouth.
- Mastication: Chewing and mixing with saliva.
- Deglutition: Food moves to the pharynx and esophagus.
- Peristalsis: Wave-like contractions move food.
- Digestion: Mechanical and chemical breakdown.
- Absorption: Nutrients pass through the GI tract.
- Defecation: Waste elimination.
The layers of the GI tract are:
- Mucosa: Inner layer with goblet cells for mucus production.
- Submucosa: Vascular with glands, nerves, and lymph nodes.
- Muscularis Externa: Responsible for peristalsis.
- Serosa: Protective outer layer.
Oral Cavity
The oral cavity includes cheeks, lips, palate, teeth, tongue, and salivary glands. It functions as a receptacle for food, enabling chewing and chemical digestion. Teeth break food into smaller parts. A tooth consists of the crown, neck, and root, with layers of enamel (hard covering), dentine (porous), pulp cavity (blood/nerves), and cementum (attachment). Humans have two sets of teeth: deciduous (20, erupt at 6 months) and permanent (32, replace from age 6 to 25). The tongue moves and mixes food, senses taste, and aids speech. It is made of skeletal muscle and papillae (some with taste buds). Salivary glands (parotid, submandibular, sublingual) produce saliva (99% water, 1% other substances) for cleaning teeth, starting digestion (enzymes: ptyalin, lysozyme), lubricating food, and killing microbes.
Pharynx and Esophagus
The pharynx is a 13 cm funnel connecting the oral/nasal cavities to the esophagus and trachea, facilitating food passage via peristalsis. The esophagus is a 25 cm muscular tube connecting the pharynx to the stomach, serving as a passageway.
Stomach
The stomach is an elastic, muscular organ with three layers (circular, diagonal, longitudinal). It consists of the cardia (upper part) and pylorus (lower part). The stomach produces gastric juice (from glands) for mechanical and chemical digestion, mainly of proteins.
Pancreas
The pancreas is a 28 cm gland behind the stomach. It has exocrine functions (produces pancreatic juice) and endocrine functions (produces hormones like insulin and glucagon).
Liver
The liver is the largest gland, reddish-brown, located on the right near the diaphragm. It has four lobes (right, left, quadrate, caudate) and produces bile (1 L/day, stored in the gallbladder). Bile contains bile salts, pigments (bilirubin), cholesterol, mucus, water, and ions. Its functions include emulsifying fats, aiding peristalsis, and removing waste. The liver also metabolizes nutrients, detoxifies blood, stores vitamins and iron, produces proteins, and converts glucose to glycogen.
Large Intestine
The large intestine is 1.5 m long and 5-8 cm wide. It includes the caecum (with appendix), colon (ascending, transverse, descending), rectum, and anal canal (with two sphincters). It reabsorbs water and salts, forms feces, and produces vitamins (K, A, B, folic acid). It contains goblet cells (mucus) and bacteria (fermentation). Flatulence results from swallowed air and digestion. The defecation reflex involves mass movement from the colon to the rectum, with sphincter relaxation.
Common Digestive Disorders
Common disorders include reflux, cancer, irritable bowel syndrome, and lactose intolerance.
Tissues: Structure and Function
- Epithelial Tissue
- Connective Tissue
- Muscle Tissue
- Nervous Tissue
Types of Connective Tissue
- Connective Proper
- Cartilage
- Bone
- Blood
Connective tissue produces 3 fibers. Smooth muscle is not under conscious control and aids in the movement of substances.
Periosteum: Dense layer of vascular tissue enveloping bones except at joints.
Bone Marrow: Red and yellow.
Carpals and Tarsals: Short bones.
Scapula: Flat bone.
Ulna: Long bone.
Ball-and-Socket Joint: Joint with a wide range of motion.
Sphenoid Bone: Cranial bone.
Occipital Bone: Not a facial skull bone.
Middle Ear Bones: Stapes, incus, malleus.
Atlas and Axis: 1st pair of vertebrae.
Manubrium: Part of the sternum.
Gout: Disease of the skeletal system.
Sarcomere: Basic contractile unit.
Tendon: Connects muscle to bone.
Smooth Muscle: Muscle found in various internal organs.
Corrugator: Facial expression muscle.
Buccinator: Not a muscle of the neck.
Internal Oblique: Back muscle.
Blood and Lymphatic System
Right Chamber: Receives oxygen-poor blood.
Red Blood Cells: Transport oxygen.
Bicuspid Valve: Located between the left atrium and ventricle.
Myocardium: Responsible for the pumping action of the heart.
Lymph Nodes: Primary lymphatic system.
Peyer’s Patches: Located in the small intestine.
Spleen: Filters blood and removes pathogens.
Additional Notes
- Connective Tissues: Connective, bone, blood, cartilage.
- Smooth Muscle: Not conscious control, helps movement.
- Short Bones: Carpals and tarsals are examples.
- Semi-movable Joint: The joints between vertebrae in the spine.
- Ball-Socket Joint: Joint with a wide range of motion.
- Sphenoid: A ceronial bone of the skull.
- Occipital: Not a facial bone.
- Sacromere: Basic muscle fiber.
- Corrugator: Muscle of facial expression.
- Right Atrium: Chamber of the heart that receives blood from the body.
- Mitral Valve: Name of the valve between the left atrium and left ventricle.
- Systematic Circulation: Type of circulation that carries oxygen-rich blood to the body.
- Myocardium: Layer of the heart primarily responsible for its pumping action.
- Blood Filtration: Role of the spleen in the lymphatic system.
- Bone Marrow: Lymphatic organ responsible for the maturation of B cells.
- Right Lymphatic Duct: Vessels that collect lymph from the lower and upper body.
- Digestion Stages: Ingestion, mastication, deglutition, peristalsis, digestion, absorption, and defecation.
- Teeth: Incisors, canines, premolars, molars.
- Sebaceous Gland: Gland that does not belong to the salivary glands.
- Stomach pH: Approximately 3.
- Amylase: Enzyme not located in the stomach.
- Small Intestine: Jejunum, ileum, duodenum.
- Liver Lobes: Right, left, caudate, quadrate.