Biology: Life on Earth (Audesirk) Nutrición y Digestión Chapter 29

APARATO DIGESTIVO El es un conjunto de órganos cuya misión primordial consiste en promover la progresión ordenada del alimento, la digestión y la absorción del mismo. Para ello, tienen que ocurrir una serie de fenómenos a lo largo de las diferentes partes que lo constituyen.

Digestión Intracelular en Esponja Biology: Life on Earth (Audesirk) Digestión Intracelular en Esponja Desechos expulsados por exocitosis a. Esponja H2O b. Célula en collar ósculo Célula en collar (a) Internal anatomy of a simple sponge, showing the direction of water flow and the location of the collar cells. (b) Enlargement of a single collar cell showing digestion of single-celled organisms, which are filtered from the water, trapped on the outside of the collar, engulfed, and digested. Entra por endocitosis Alimento filtrado por célula collar H2O con alimento entra por poros Fusión con lisosoma Chapter 29

Digestión en un Saco:Hydra Biology: Life on Earth (Audesirk) Tentáculos Boca A Hydra has just captured and ingested a waterflea (Daphnia, a microscopic crustacean). a. Sponge Within the gastrovascular cavity of Hydra, gland cells secrete enzymes that digest the prey into smaller particles and nutrients. Elongated cells lining the cavity ingest these particles by intracellular digestion (see Fig. 29-4), and digestion is completed intracellularly. Undigested waste is then expelled through the single opening. Células nutritivas Células Glandulares Crustáceo Ingerido Cavidad Gastrovascular Chapter 29

Tracto Digestivo Tubular: Lumbricus Biology: Life on Earth (Audesirk) Intestino Ano Boca The earthworm has a one-way digestive system that passes food through a series of compartments, each specialized to play a specific role in breaking down food and absorbing it. Faringe Esófago Buche Molleja Chapter 29

Sistema Digestivo Humano Boca Descomposición mecánica y química de los alimentos Glándulas Salivales Producen saliva, enzimas y anticuerpos Lubrican el alimento para tragarlos Esófago Tubo muscular que conecta la boca con el estómago Propulsa el bolo alimenticio por peristaltismo

El tracto digestivo humano Biology: Life on Earth (Audesirk) El tracto digestivo humano Glándulas Salivales Epiglotis Estómago Páncreas Esófago The digestive system includes both the digestive tube and organs such as the salivary glands, liver, gallbladder, and pancreas, all of which produce and store digestive secretions. The stomach has a muscular wall and folds that allow expansion. Faringe Hígado Vesícula biliar Intestino delgado Colon: Ascendente Transverso Descendente Recto Chapter 29

Estómago humano Saco muscular expansible Esfínter pilórico en su parte baja Almacena alimento; gradualmente lo envía hacia el duodeno Tritura mecánicamente partículas grandes de alimento Descompone químicamente el alimento utilizando sus enzimas Pepsinógeno y pepsina Mucus—barrera protectora de su autodigestión Quimo—alimento parcialmente digerido y secreciones Pasa agua, drogas y alcohol directamente a la sangre.

El estómago Capa de músculos Esfínter pilórico Duodeno

Intestino delgado Tubo largo, estrecho y enrollado con una gran superficie de contacto Continúa la digestión con secreciones que recibe de: HIGADO: Bilis producida por el hígado , y se almacena en Vesícula PÁNCREAS El jugo pancreático neutraliza al quimo ácido Amilasa pancreática para la digestión de carbohidratos Lipasa para la digestión de lípidos Proteasas, tripsina y quimotripsina para la digestión de proteínas Absorción facilitada por vellosidades y microvellosidades

Intestino grueso Restos de la digestión Se concentra Se transporta hacia el recto donde se almacena Defecación Su población de bacterias sintetizan Vitamina B12 Tiamina Riboflavina Vitamina K

Dientes adaptados a diferentes dietas Biology: Life on Earth (Audesirk) Incisivos Caninos Premolares Molares (a) The varied, omnivorous diet of humans has fostered the evolution of an unspecialized dentition that includes flat incisors for biting, pointed canines for tearing, premolars for grinding, and molars for crushing and chewing. (b) Carnivores (such as the lion) have modest incisors but greatly enlarged canines for stabbing and tearing flesh. Carnivores also have a reduced set of cheek teeth (molars and premolars) that are specialized for shearing through tendon and bone. (c) Herbivores (such as the cow) have incisors that are specialized for snipping leaves, and their canines have been reduced in size and moved forward to help with that job. The cheek is filled with a full set of wide, flat premolars and molars that grind up the tough, cellulose-containing plant material. Omnívoros Carnívoros Herbívoros Chapter 29

Biology: Life on Earth (Audesirk) El desafío de tragar (a) Swallowing is complicated by the fact that both the esophagus (part of the digestive system) and the larynx (part of the respiratory system) open into the pharynx. (b) During swallowing, the larynx moves upward beneath a small flap of cartilage, the epiglottis. The epiglottis folds down over the larynx, sealing off the opening to the respiratory system and directing food down the esophagus instead. Chapter 29

Biology: Life on Earth (Audesirk) Peristaltismo Food is propelled through the digestive system by the rhythmic contractions of circular and longitudinal muscles. Chapter 29

Area superficial intestino delgado 1° y 2º niveles Biology: Life on Earth (Audesirk) Area superficial intestino delgado 1° y 2º niveles Intestino The folds of the small intestine maximize the surface area available to absorb nutrients. Macroscopic folds in the intestinal lining are themselves carpeted in (b) tiny, fingerlike projections called villi. Vellosidades Pliegue de la mucosa intestinal Chapter 29

Area superficial intestino delgado 2º nivel Biology: Life on Earth (Audesirk) Area superficial intestino delgado 2º nivel Vellosidades Red Capilar Villi enclose a network of capillaries and lymph vessels. Quilífero Glándula intestinal Arteriola Linfático Vénula Chapter 29

Area superficial intestino delgado: 2º y 3° niveles Biology: Life on Earth (Audesirk) Area superficial intestino delgado: 2º y 3° niveles Microvellosidad Una vellosidad If we use a microscope to zoom in on one villus, we see that the epithelial cells on its surface are sheathed in plasma membranes that have yet another level of microscopic projections, microvilli. una célula epitelial Chapter 29